Help! Troubleshooting Code 36 and Running Rough

[tonybabb]

This is driving me nuts ! My 89 coupe, that I bought new in 89, is not feeling well and I'm trying to help it get better. I've been getting a code 36 (Mass Airflow Sensor Burn-off Relay), it's been running fine except for the Check Engine Light. So, I've replaced the Mass Airflow Sensor, the MAF Burn-off relay, the MAF power relay. None of this fixed the problem, a few weeks ago I also replaced the plugs, plug wires, distributor cap and rotor as part of regular maintenance. A couple of days ago it started running rough, it idles just fine but under load (acceleration or cruise) it feels and sounds like it's running on 7 cylinders, the coolant is also running 8 - 10 degrees cooler. I checked the plug wires, replaced the ignition module. I'd really appreciate some advice on how to troubleshoot the rough running so then I can get back to tracking down the code 36 problem as I'm assuming these two problems are unrelated.

Thanks,

Tony

 

[vigman]

Tony.. do you have a shop manual?

If not... I'll try to scan my 88 manual for code 36 step by step...
Mike

Short answer... replace BOTH relays.. check the ground to chassis connection on the frame rail near the master cylinder
CLEAN ALL CONNECTIONS... and make sure none of the relay connections nor maf sensor connections are funky....

And from C4C5
"This code is for the burnoff function of the MAF.
Basically, this is how it works, once you turn off your engine after a minimum of a 10 min drive. The burnoff function will enable. This will induce 12 volts to the hot wire sensing element, and will make it glow red to 'burnoff' the contamination that may stick to the wire.
Now, according to that, you might want to run the car in your driveway for about 15 mins, and have the front of the MAF off of the airbox. Have someone turn off the car, and you look inside the MAF, You should see the wire in the center of the MAF glow red within a minute or 2. It may last about 15 sec, so watch carefully.
If you dont see anything within the MAF, try this.
Take your multimeter, and monitor the drk blue wire, when your friend shuts off the motor, this should go 12 volts, once the engine is turned off."

OP post "How long should that blue wire go to twelve volts? The manual say for about one second which it does that."

C4C5
"Ok, thats fine. Now, check for 12 volts at the purple wire. For the same amount of time."

OP
"Ok I have voltage on purple for one sec also. Is this enough time for the burnoff?"

C4C5
"honestly, then I would check your grounding circuit, to make sure that the 900 circuit, which grounds your burnoff relay is constant, as I am suspecting a problem. if your ground source is longer than your on time of the burnoff relay, therein may be your issue.
1 second usually isnt what I see, it is usually 5 sec, from what I remember.
I have a feeler out for actual on time, but I believe it is 5 seconds."

And a lot more here.....
http://www.corvetteactioncenter.com...ormance/6389-code-36-maf-burnoff-circuit.html

From other places

I purchased my ’89 new and have a few observations re connectors, including ones that give a code 36 and dash lights to misbehave. Clean both sides of connectors well including spraying them out with a fast drying pressurized contact cleaner. A small pencil eraser, cut to a handy shape, works to clean up any metal parts of the connector you can get to, this helps to get a good electrical connection. Use the small tube that comes with cleaner to flush them out well a couple of times. Place a rag under the connector to catch the run off. If the connector has a weather ring around it, smear a little silicon grease on the ring, it will make the connector go together easier, help to get it fully seated and make a better seal. Sometimes it just a bad connection.

86 PDF ( 89 similar )
http://members.shaw.ca/corvette86/Engine to ECM Wiring Diagram 86.pdf

AND

there are two relays.. behind battery.. one is the burn off relay and the other is the power relay, which powers the Maf, should this relay fail, the ecm will set code 33, The MAF MUST be powered for ecm to read..if the ecm cant , will not send command to burn off relay,,hence first code 33,,burn off fail, To check that the MAF burn-off is getting power, look for 12 volts at the MAF connector position E If you get a Code 36, MAF burn-off malfunction, it should immediately reveal itself at startup and it won't affect performance. '85 Corvettes will never show a Code 36, only '86-'89 Corvettes. You can check to see if the ECM is calling for an MAF burn-off by running the car for at least 5 minutes, and checking the black wire at connection F (circuit 900) on the gray connector. It should be grounded for approximately 30 seconds. This is the ECM grounding the wire to actuate the relay. If there is no ground, the ECM is at fault. If you have ground, check the power to the relay. If the relay is sending power to the MAF, check that the dark blue wire (position D) on the MAF sensor connector has power. change both relays,,the parts number hopefully still readable on old ones..i cant recall if both relays are the same (Over the years, some changes were made to the relays for the MAF. The '86 and early '87 relay for MAF power was PN 100067925; the burn-off relay was PN 10094701.__) The relays changed in late '87. Relay No. 14089936 operated the MAF power, burn-off, and fuel pump. Although not always accurate, the connectors for the 9936 relay are the gray connector for the burn-off circuit and the black connector for the MAF power circuit chasing down several specific reasons why Codes 34 and 33 will appear. The dark green wire from the ECM to the MAF (circuit 998) can short to ground or short together with circuit 450 (black or black/white) and cause a Code 34. To get a Code 33, circuits 998 or 450 could have an open circuit. Recently, the only cure was to run new wires for both circuits. This cured the intermittent codes immediately.

 

[tonybabb]

Thanks, I have the manual..

The timings you quote are very helpful, looking through my manual it says run it until it goes "closed loop" but doesn't explain what "closed loop" means. I'll try this tonight/ tomorrow. Do you think this could be connected to the rough running? Somehow I don't think so as I've had the code 36 for a couple of weeks now but the rough running only started a couple of days ago. I'm thinking to check throttle Position Sensor next and then fuel - fuel will be hard as I think it could show 40+ lbs pressure but may be blocked and so unable to flow enough. Even at light throttle settings it runs rough so I'm thinking the TPS is most likely. When in Park/ Neutral it's fine even when I just put it in Drive it sounds rough.
Thanks again,

Tony

If not... I'll try to scan my 88 manual for code 36 step by step...
Mike

And from C4C5
"This code is for the burnoff function of the MAF.
Basically, this is how it works, once you turn off your engine after a minimum of a 10 min drive. The burnoff function will enable. This will induce 12 volts to the hot wire sensing element, and will make it glow red to 'burnoff' the contamination that may stick to the wire.
Now, according to that, you might want to run the car in your driveway for about 15 mins, and have the front of the MAF off of the airbox. Have someone turn off the car, and you look inside the MAF, You should see the wire in the center of the MAF glow red within a minute or 2. It may last about 15 sec, so watch carefully.
If you dont see anything within the MAF, try this.
Take your multimeter, and monitor the drk blue wire, when your friend shuts off the motor, this should go 12 volts, once the engine is turned off."

OP post "How long should that blue wire go to twelve volts? The manual say for about one second which it does that."

C4C5
"Ok, thats fine. Now, check for 12 volts at the purple wire. For the same amount of time."

OP
"Ok I have voltage on purple for one sec also. Is this enough time for the burnoff?"

C4C5
"honestly, then I would check your grounding circuit, to make sure that the 900 circuit, which grounds your burnoff relay is constant, as I am suspecting a problem. if your ground source is longer than your on time of the burnoff relay, therein may be your issue.
1 second usually isnt what I see, it is usually 5 sec, from what I remember.
I have a feeler out for actual on time, but I believe it is 5 seconds."

And a lot more here.....
http://www.corvetteactioncenter.com...ormance/6389-code-36-maf-burnoff-circuit.html

From other places

I purchased my ’89 new and have a few observations re connectors, including ones that give a code 36 and dash lights to misbehave. Clean both sides of connectors well including spraying them out with a fast drying pressurized contact cleaner. A small pencil eraser, cut to a handy shape, works to clean up any metal parts of the connector you can get to, this helps to get a good electrical connection. Use the small tube that comes with cleaner to flush them out well a couple of times. Place a rag under the connector to catch the run off. If the connector has a weather ring around it, smear a little silicon grease on the ring, it will make the connector go together easier, help to get it fully seated and make a better seal. Sometimes it just a bad connection.

86 PDF ( 89 similar )
http://members.shaw.ca/corvette86/Engine to ECM Wiring Diagram 86.pdf

AND

there are two relays.. behind battery.. one is the burn off relay and the other is the power relay, which powers the Maf, should this relay fail, the ecm will set code 33, The MAF MUST be powered for ecm to read..if the ecm cant , will not send command to burn off relay,,hence first code 33,,burn off fail, To check that the MAF burn-off is getting power, look for 12 volts at the MAF connector position E If you get a Code 36, MAF burn-off malfunction, it should immediately reveal itself at startup and it won't affect performance. '85 Corvettes will never show a Code 36, only '86-'89 Corvettes. You can check to see if the ECM is calling for an MAF burn-off by running the car for at least 5 minutes, and checking the black wire at connection F (circuit 900) on the gray connector. It should be grounded for approximately 30 seconds. This is the ECM grounding the wire to actuate the relay. If there is no ground, the ECM is at fault. If you have ground, check the power to the relay. If the relay is sending power to the MAF, check that the dark blue wire (position D) on the MAF sensor connector has power. change both relays,,the parts number hopefully still readable on old ones..i cant recall if both relays are the same (Over the years, some changes were made to the relays for the MAF. The '86 and early '87 relay for MAF power was PN 100067925; the burn-off relay was PN 10094701.__) The relays changed in late '87. Relay No. 14089936 operated the MAF power, burn-off, and fuel pump. Although not always accurate, the connectors for the 9936 relay are the gray connector for the burn-off circuit and the black connector for the MAF power circuit chasing down several specific reasons why Codes 34 and 33 will appear. The dark green wire from the ECM to the MAF (circuit 998) can short to ground or short together with circuit 450 (black or black/white) and cause a Code 34. To get a Code 33, circuits 998 or 450 could have an open circuit. Recently, the only cure was to run new wires for both circuits. This cured the intermittent codes immediately.

 

[vigman]

Tony

Do you have a K & N or after market air cleaner ? ( Hint here, ones that use spray oil ).
Have you used MAF cleaner on the MAF internals?

Are the MAF and relays GM or other ( auto zone etc etc ) ?
recheck you wiring.. a wire might have popped off a plug or got burnt to close to the exhaust...

run it at night... hood open.. and look for the light show

Is 36 the only " current " code you have?

Open loop= car is not listening to the O2 sensors and running off an internal map ( till it warms up ).

Closed loop= Car is up to temp.. and is closing the loop ( intake to exhaust ) listening to the O2's and making engine corrections based on the O2's output.

Mike

 

[Schrade]

vig is right on Closed Loop - computer gets a signal from the coolant temp sensor that a designated temp is reached. THen the computer reduces pulsewidth of the injectors (less fuel), and it also gets a reading from all sensors for normal operating parameters. Anything out of range sets a DTC; sometimes after one instance, sometimes after 4 instances, etc.

Why did you replace all those parts? Was the current coming to them good? And all the ground connections FROM them good too?

 

[tonybabb]

Mike,

The air cleaner is Fram, I think. haven't tried MAF cleaner, I'll get some though and report back. The new relays are from Autozone, no idea of the manufacturer, the MAF is Bosch. All wires look good to me. I did remove and replace the TPS wire connector today, it seems to have made a difference at least for a while. When I back out of my garage it sounds smooth, previously it was rough as soon as I put it into reverse, it was also smooth going up the hill outside - I thought I had fixed it but a few minutes later going down the freeway it felt and sounded rough again, more like a surging feeling than a misfire though. I'll revisit the TPS connector tomorrow though just to be sure. I'll also run it at night and look for the light show.

Code 36 is the only code I'm getting.

Thanks,

Tony

Do you have a K & N or after market air cleaner ? ( Hint here, ones that use spray oil ).
Have you used MAF cleaner on the MAF internals?

Are the MAF and relays GM or other ( auto zone etc etc ) ?
recheck you wiring.. a wire might have popped off a plug or got burnt to close to the exhaust...

run it at night... hood open.. and look for the light show

Is 36 the only " current " code you have?

Open loop= car is not listening to the O2 sensors and running off an internal map ( till it warms up ).

Closed loop= Car is up to temp.. and is closing the loop ( intake to exhaust ) listening to the O2's and making engine corrections based on the O2's output.

Mike

 

[tonybabb]

Schrade,

Thanks. I replaced all the parts while I was replacing a cylinder head gasket - previously replaced both gaskets about 3 - 4 years ago. I had a coolant leak a couple of months ago, didn't take care of it and blew the gasket......so I figured while I was there I'd replace the plugs/ wires etc. I haven't checked the grounds, I guess that's next.

As I mentioned originally, I was getting a code 36 for a week or so after the cylinder head gasket was replaced - the code comes on after about 4 - 6 trips in the car - ie start from cold, get it hot then turn off, let it cool. The rough running started a few days ago so i'm assuming I have two separate problems - sound reasonable?

Thanks again,

Tony

vig is right on Closed Loop - computer gets a signal from the coolant temp sensor that a designated temp is reached. THen the computer reduces pulsewidth of the injectors (less fuel), and it also gets a reading from all sensors for normal operating parameters. Anything out of range sets a DTC; sometimes after one instance, sometimes after 4 instances, etc.

Why did you replace all those parts? Was the current coming to them good? And all the ground connections FROM them good too?

 

[vigman]

2 seperate issues....

Autozone MAF relays... nahhhhh
Bosh MAF... well I did that and it worked...
Misfire... thinking plug wires...
Surging.. that a different dealio...
Unplugging TPS.. who knows, maybe good idea to measure its resistance.... or voltage in circuit..
Is it original.. the TPS?

So exactly what did you do during this tune up?
How many miles on the car?

(Don't want to sound like the inquisition... but more facts on the table will help )

Mike

 

[John Robinson]

Since the way it ran changed when you played with TPS try this. The next time it is running bad shake and move the TPS wires and the wiring harness to see if that changes the way it runs. The wires on those sensors are very small and will brake from age and vibration. And be aware that the TPS the Temp sensor the MAF sensor and the air intake sensor all go back to a common ground in the wiring harness. If your harness is like mine you will find a place were the ground wires all go into a wad of electrical tape. Remove the tape and I bet you will find that the common connection is corroded and maybe even wet from condensation. If so you will have to cut the wires and reconnect them with a good solder joint. Since all those sensors use a common ground point and the ecm uses the ground voltage to determine how to set up the engine. The code you get may not be the real problem it just may be that the signal that is missing for the ecm is the code 36 only because it is being lost in a bad wire or ground. The problem with codes is they only show up because something is wrong in that circuit and the ECM can not tell you to look at something like a bad wire. Put another way if you run a fever because you cut yourself and got an infection. The Doctor would look for the source of the fever and treat it.

 

[vigman]

Tony has this always been a Calif car?

Or did you wash the engine bay recently...?

Good Points John!

Mike

 

[boomdriver]

Try getting a handful of the left side wire harness at or directly behind the valve covers where it runs from the firewall to the valve cover to distribute fuel injector plugs....
wiggle that around and restart. IF you think there is a difference, continue to move that section around gently and confirm.

That section which also holds the MAF wires, and the coolant sensor and all the inj plugs, is spliced into the main harness on the firewall. It gets pulled and tugged and these splices are fragile. They DO come apart and the insulation does break and then you have cross signaling in the harness.

If you are seeing a MAF code and have replaced everything (?) then it comes down to wire, connections or plugs. the MAF plug itself is prone to the wire pulling out of the pin within the plug where it cannot be seen. I have replaced that particular plug twice on my current C4.

The rotting wire syndrome is common in the C4. Poor quality wire/insulation , the plastic sleeve dries out and then breaks open exposing wire to each other in the bundle. They do not have to touch..just be near...auora effect. Because these cares are 100% managed by electrical resistence and reference voltage, any dirty, corroded or loose contact will result in misinformation to the ECM or control device.
Your grounds for all your critical systems also come from splices in the exact same harness section within 2" of the EFI wires and MAF wires..so there are LOTS of splices in one spot and they are all the most sensitive systems on the car. Your harness grounds should also be cleaned and physically looked at. They run from behind the left valve cover harness down to a bolt on or near the oil filter. 4 or 5 wires on one bolt. Those are the most important grounds on the car.

Also, just unplug the MAF and start it and make it run 8 seconds...that may be difficult at first but this forces it to run OL and that way you can demonstrate and isolate the problem. It should run fine. That proves that its a sensor issue either thru signal, transmission of, or connectivity. Your descriptions sounds exactly like a BAD MAF, so focus on proving it !
Also, swap the burn and power relay. The burn does not matter to a running engine. They DO sell bad relays....

 

[Schrade]

Cold motor performance means NOTHING. I don't know how else to put that - ONLY idle quality of a warm motor tells anything... If you have a vacuum leak, NOTHING else sould be addressed. A vacuum leak will show itself on a WARM motor, as a loping idle, up and down RPM's. NOTHING else means ANYTHING, if there's a vacuum leak. NO cold motor operation, Codes, on a COLD motor, they mean NOTHING, if you have a vacuum leak... ANYTHING on a COLD motor means absolutely ZERO. IT HAS TO BE WARMED UP !!!

 

[tonybabb]

Still running rough and code 36

Cold motor performance means NOTHING. I don't know how else to put that - ONLY idle quality of a warm motor tells anything... If you have a vacuum leak, NOTHING else sould be addressed. A vacuum leak will show itself on a WARM motor, as a loping idle, up and down RPM's. NOTHING else means ANYTHING, if there's a vacuum leak. NO cold motor operation, Codes, on a COLD motor, they mean NOTHING, if you have a vacuum leak... ANYTHING on a COLD motor means absolutely ZERO. IT HAS TO BE WARMED UP !!!

OK, I had a chance to look at it again this evening. I still have a code 36 (MAF Burn-off Relay) and it runs rough whenever it's under load, cold or warm. I'm assuming these are unrelated problems, I'm assuming the code 36 won't cause these rough running symptons but just in case I've already replaced the MAF sensor, burn-off relay and power relay so maybe I've got a bad wire somewhere - I checked and can see the MAF glowing when I turn off the motor, it sets the code 36 when I've done 5 or 6 trips in it, not the first few times I use it.

For now I'm focussed on the rough running, when it idles it is perfect, also I can rev it to 1500 and also 2300 rpm and it sounds perfect every time. As soon as I put it into "Reverse" or "Drive" it runs rough, as though it's only on 7 cylinders, when accelerating hard or easy and cruising it runs rough. To summarize, in the past few weeks I've replaced the plugs, plug wires, distributor cap, rotor, ECM, fuel filter and thermostat(180f). I've also put in a couple of cans of fuel injector cleaner. This evening I ohmed the injectors and all checked out at 17-3 - 17.6, so I think they're OK.

As far as I can see the earths are fine, but I haven't taken any off to check. So, where to go next. I'm thinking about taking it to the garage and have them hook up their computer and tell me what's going on - I hate to admit I'm stumped but I'm stumped.

Thanks,

Tony

 

[John Robinson]

I don't see were you tried to shake the wires when it was running rough. This information is from my 93 fsm but it will explain what the tps function is. You will note the tps can cause the ecm to provide burst of fuel. That translates to a rough idle. If you have a broken wire in the tps circuit then when it is moving from vibration it will have the ecm going crazy with supplying bursts of fuel evertime the wires touch and send a signal to the ecm.

Hope this sheds some light on the tps for you

---

​

Throttle Position Sensor (TPS)
Copied from 1993 Service Manual
The Throttle Position sensor (TPS) is a potentiometer connected to the throttle shaft on the throttle body. It is a potentiometer with one end connected to 5 volts
from the ECM and the other to ECM ground. A third wire is connected to the ECM to measure the voltage from the TP sensor. As the throttle valve angle is changed (accelerator pedal moved), the voltage output of the TP sensor also changes. At a closed throttle position, the voltage output of the TP sensor is low (approximately .5 volt). As the throttle valve opens, the output voltage should be approximately 5 volts.

By monitoring the output voltage from the TP sensor, the ECM can determine fuel delivery based on throttle valve angle (driver demand). A broken or loose TP sensor can cause intermittent burst of fuel from the injectors and cause an unstable idle, because the ECM detects the throttle is moving.

If the TP sensor circuit is open, the ECM will set a DTC 22. If the TP sensor circuit is shorted a DTC 21 will be set. A problem in any of the TP sensor circuits will set either a DTC 21 or 22. Once a DTC is set, the ECM will use a default value for TP sensor, and some vehicle performance will return.

A personal note, when my TPS failed it DID NOT set a code other than to tell me the ECM was bad.

---

​

 

[tonybabb]

Thanks

Try getting a handful of the left side wire harness at or directly behind the valve covers where it runs from the firewall to the valve cover to distribute fuel injector plugs....
wiggle that around and restart. IF you think there is a difference, continue to move that section around gently and confirm.

That section which also holds the MAF wires, and the coolant sensor and all the inj plugs, is spliced into the main harness on the firewall. It gets pulled and tugged and these splices are fragile. They DO come apart and the insulation does break and then you have cross signaling in the harness.

If you are seeing a MAF code and have replaced everything (?) then it comes down to wire, connections or plugs. the MAF plug itself is prone to the wire pulling out of the pin within the plug where it cannot be seen. I have replaced that particular plug twice on my current C4.


The rotting wire syndrome is common in the C4. Poor quality wire/insulation , the plastic sleeve dries out and then breaks open exposing wire to each other in the bundle. They do not have to touch..just be near...auora effect. Because these cares are 100% managed by electrical resistence and reference voltage, any dirty, corroded or loose contact will result in misinformation to the ECM or control device.
Your grounds for all your critical systems also come from splices in the exact same harness section within 2" of the EFI wires and MAF wires..so there are LOTS of splices in one spot and they are all the most sensitive systems on the car. Your harness grounds should also be cleaned and physically looked at. They run from behind the left valve cover harness down to a bolt on or near the oil filter. 4 or 5 wires on one bolt. Those are the most important grounds on the car.

Also, just unplug the MAF and start it and make it run 8 seconds...that may be difficult at first but this forces it to run OL and that way you can demonstrate and isolate the problem. It should run fine. That proves that its a sensor issue either thru signal, transmission of, or connectivity. Your descriptions sounds exactly like a BAD MAF, so focus on proving it !
Also, swap the burn and power relay. The burn does not matter to a running engine. They DO sell bad relays....

I really appreciate the detailed wiring description, I'll start checking that out next, although I'm not sure how i can check the wires in the insulated bundle, should I remove all the insulation? When I'm done what should I replace it with? I've already replaced the MAF and burn-off relay and power relay and swapped the old and new relays.

Thanks again,
Tony

 

[tonybabb]

Thanks

I don't see were you tried to shake the wires when it was running rough. This information is from my 93 fsm but it will explain what the tps function is. You will note the tps can cause the ecm to provide burst of fuel. That translates to a rough idle. If you have a broken wire in the tps circuit then when it is moving from vibration it will have the ecm going crazy with supplying bursts of fuel evertime the wires touch and send a signal to the ecm.

Hope this sheds some light on the tps for you

---

​

Throttle Position Sensor (TPS)
Copied from 1993 Service Manual
The Throttle Position sensor (TPS) is a potentiometer connected to the throttle shaft on the throttle body. It is a potentiometer with one end connected to 5 volts
from the ECM and the other to ECM ground. A third wire is connected to the ECM to measure the voltage from the TP sensor. As the throttle valve angle is changed (accelerator pedal moved), the voltage output of the TP sensor also changes. At a closed throttle position, the voltage output of the TP sensor is low (approximately .5 volt). As the throttle valve opens, the output voltage should be approximately 5 volts.

By monitoring the output voltage from the TP sensor, the ECM can determine fuel delivery based on throttle valve angle (driver demand). A broken or loose TP sensor can cause intermittent burst of fuel from the injectors and cause an unstable idle, because the ECM detects the throttle is moving.

If the TP sensor circuit is open, the ECM will set a DTC 22. If the TP sensor circuit is shorted a DTC 21 will be set. A problem in any of the TP sensor circuits will set either a DTC 21 or 22. Once a DTC is set, the ECM will use a default value for TP sensor, and some vehicle performance will return.

A personal note, when my TPS failed it DID NOT set a code other than to tell me the ECM was bad.

---

​

It idles perfectly and also revs at 1500 and 2300 rpm perfectly, the problems start when I put it in Reverse or Drive and continue when I'm accelerating or cruising. Engine hot or cold makes no difference.

Thanks again,

Tony

 

[John Robinson]

Start by pulling the wires out of the black wire run. Carefully start with the wires going into the run and pull them out until you get to the wire bundle. You will regognize it because it is wrapped in electrical tape. One at a time cut a wire and check it for continuity back to the connector it is attached to. DO NOT BACK PROBE ANY WIRE FOR CONTINUITY TO THE ECM. THE BATTERY IN YOUR meter can FRY THE ECM UNLESS YOU HAVE DISCONNECTED ALL THE PLUGS GOING INTO THE ECM. All you need to check is the continuity from the ground bundle back towards whatever sensor it is connected to.

Good luck and don't underestimate the problems the wiring can cause. Forget anything you think you know about what makes an engine run. The C4 Corvette introduced a whole new concept in engine management control. In fact GM did not come up with the system they got it from Bosch and it is very similiar to what is on the BMW. I will be off the air for awhile since I am having surgery in about 4 hours

 

[tonybabb]

John,

Start by pulling the wires out of the black wire run. Carefully start with the wires going into the run and pull them out until you get to the wire bundle. You will regognize it because it is wrapped in electrical tape. One at a time cut a wire and check it for continuity back to the connector it is attached to. DO NOT BACK PROBE ANY WIRE FOR CONTINUITY TO THE ECM. THE BATTERY IN YOUR meter can FRY THE ECM UNLESS YOU HAVE DISCONNECTED ALL THE PLUGS GOING INTO THE ECM. All you need to check is the continuity from the ground bundle back towards whatever sensor it is connected to.

Good luck and don't underestimate the problems the wiring can cause. Forget anything you think you know about what makes an engine run. The C4 Corvette introduced a whole new concept in engine management control. In fact GM did not come up with the system they got it from Bosch and it is very similiar to what is on the BMW. I will be off the air for awhile since I am having surgery in about 4 hours

Thanks, did you mean literally to "cut" the wire?
Good luck with the surgery

 

[John Robinson]

Thanks, did you mean literally to "cut" the wire?
Good luck with the surgery

Yes cut the wire. That is if you find the bundle and it is gray and corroded you are going to have to redo the bundle by cutting each wire loose and remaking the connection by soldering all the wires to a new common connection. One wire at a time and use some masking tape to mark and number each wire so you get it back together correctly. If your skill level is being pushed with doing wiring and continuity testing then get someone who works with electronic repairs to check it out. Maybe a neighbor or friend or even a relative.

 

[vigman]

Do not believe your eyes.....

The quality of an electrical connection needs to be measured... ( unless your superman.. LOL )
So frame grounds, need to be removed, wire brushed, sanded, a little dielectric grease won't hurt and put back down...

Measure from the batt neg to the frame... it should be VERY close to an ohm or 2.... the repeat from Batt neg to engine block.. same deal.

Has you battery ever leaked.. the power distro block is right under there.... and all the fusible links are there too...

I had 2 links that were marginal causing weird intermittants..My chassis to engine ground was funky...
Have to start with the basics... if you assume... you could be chasin' your tail for quite some time ... like I did.

The TPS is no different then an old volume controlin the funky garage radio....
You know the one..... you turn up... and scratch... scratch... ( volume goes down ) scratch...

Your TPS might be doing the same thing sending a bad signal to the ECU...and TPS's do not like sitting..
But you do not know anything till the basics are checked...

Mike

PS I agree with John, the internal harness grounds connections are a bit dodgy... I had to re do one in my 84....