ECM Removal

[Tommy Almond]

Hey guys, thinking of getting rid of all my ECM operated system. Seems fix one thing and another pops up. Mechanical I can adjust but this darn ECM controls items I can't change. Been having problems with sluggish accerlaration at take off. Vette runs well once taken off from dead start, just a terrible hole shot.
Has anyone removed the ECM? I know a change of carb and dist. is needed, what would I need to address? Trans lockup is one item I know of, what about the ERG valve and other parts?
I'm between painting the vette or swapping out the ECM so any comments will be great.

 

[tmkassin]

You should start by telling us what year and model Vette you are working on.

 

[Tommy Almond]

You should start by telling us what year and model Vette you are working on.

I posted this on the L-81 Forum, so figure all posts here were for the 81. But if not it is a 1981 vette w/stock 350 engine, auto 350 trans.

 

[bill81vette]

I would have (hate to use the word)assumed it was an 81 !

1st welcome to CAC!!!!
2nd..are these your only symptoms..
almost sounds like a carb adjustment to me...but wait till sensi sees this he's the carb expert!!!

 

[spikebot 81]

I removed all the senors ecm and wiring on my 81 and glad I did. Components kept failing sending bad signals to the fred flintstone type computer so enough was enough. The cost is high if you go the route I took. New carb, dist, intake manifold, headers, duals. But now I have control of the engine tuning and not fred. The lockup torque converter will not work without some mods and there are several ways to address this. Do a search on tcc lockup and pick method that works best for you.

 

[Tommy Almond]

I would have (hate to use the word)assumed it was an 81 !

1st welcome to CAC!!!!
2nd..are these your only symptoms..
almost sounds like a carb adjustment to me...but wait till sensi sees this he's the carb expert!!!

Yes the sluggish take off is the main problem. If I set the rpm up to about 800 in drive she takes off fine, good power and accerleration, but lower rpm she just hestiates for a few seconds before she picks up. I installed a new rebuilt q-jet from Ecklers last month. Problem was not there afterward, just came back last day or two so thinking something in the ECM is causing some problem.

 

[Sensei]

Yes the sluggish take off is the main problem. If I set the rpm up to about 800 in drive she takes off fine, good power and accerleration, but lower rpm she just hestiates for a few seconds before she picks up. I installed a new rebuilt q-jet from Ecklers last month. Problem was not there afterward, just came back last day or two so thinking something in the ECM is causing some problem.

I can almost guarantee the problem is NOT the ECM, but you have to do some simple diagnostics to know where the problem is. Otherwise you are just guessing, which leads to a lot of frustration, a lot of wasted money and often without ever getting the real problem fixed.

A commercially rebuilt carb (like you got from Eklers) will be built with a lot of shortcuts that often make the carb unusable in the long run.
The first thing I would check is the accelerator pump. With the engine off and air cleaner removed, look down the primary bores, move the throttle and there should be an immediate, strong, squirt gun like shot of gas in each bore. If the shot hesitates, sputters or is weak, the problem is either (in order of probability) 1. Bad pump plunger (easy fix), 2. debris in pump channel (PITA, but it does not cost anything), 3. damaged pump well (this one is rare, usually caused by bad rebuilder)

If your pump shot is good, the next thing to check is the secondary air valve adjustment. (Before I go into this proceedure, check your pump shot.)

Otherwise, get a GM Service Manual and follow the diagnostic litanies. But overall, the ECM and it's related components, including the E4ME carb are all very reliable and inexpensive to repair vs replacing everything with parts that will have absolutely no benefits in performance or reliability and will be less efficient!

God bless, Sensei

 

[Tommy Almond]

I can almost guarantee the problem is NOT the ECM, but you have to do some simple diagnostics to know where the problem is. Otherwise you are just guessing, which leads to a lot of frustration, a lot of wasted money and often without ever getting the real problem fixed.

A commercially rebuilt carb (like you got from Eklers) will be built with a lot of shortcuts that often make the carb unusable in the long run.
The first thing I would check is the accelerator pump. With the engine off and air cleaner removed, look down the primary bores, move the throttle and there should be an immediate, strong, squirt gun like shot of gas in each bore. If the shot hesitates, sputters or is weak, the problem is either (in order of probability) 1. Bad pump plunger (easy fix), 2. debris in pump channel (PITA, but it does not cost anything), 3. damaged pump well (this one is rare, usually caused by bad rebuilder)

If your pump shot is good, the next thing to check is the secondary air valve adjustment. (Before I go into this proceedure, check your pump shot.)

Otherwise, get a GM Service Manual and follow the diagnostic litanies. But overall, the ECM and it's related components, including the E4ME carb are all very reliable and inexpensive to repair vs replacing everything with parts that will have absolutely no benefits in performance or reliability and will be less efficient!

God bless, Sensei

Pump shot into the front chambers are strong. Car had not been cranked since Sunday and tonight before cranking I tested the pump shot and both chambers were strong.
I had the ECM checked out at the local Chevy dealer in May and they advised I had input going into the ECM but not coming out, check engine light did not work. They also said the original carb was shot, so that is why the replacement installed.
I purchased a new ECM from NAPA and installed it along with a new Hypertech power chip/prom so I am not running the original prom. My Chevy mechanic recommended to get a new prom if could. So any thoughts on that new prom? Should I go back to the original?
Check engine light now works. Sometimes I get a light sometimes when sitting at a red light but goes off once start moving again. Pulled code and was 13, O2 sensor system.
Also last month had the whole fuel system serviced, cleaned out fuel tank, installed new tank screen, blew out lines to fuel pump, installed new fuel pump and new line from pump to carb and insulated line w/500 degree heat wrap.
Car ran strong for a while then just started being sluggish again on take off; Saturday one time it felt as if when I pushed the gas pedal the engine had no change in rpm.
Since most parts are probably not been changed in a while (I got the car last Sept.) I am changing ERG, PCV and replacing vacuum hoses as needed. Just mainly for piece of mind to know I have good working parts. I have the shop manual for the '81 and it does mention the ERG as possibly sticking to cause sluggish accerlation so will install new one tomorrow.
I do thank you for all your help and look forward to any other comments or suggestion. I hear on here you are "the man" so I feel honor to have you reply to my post.

 

[Tom Bryant]

I see you got a code 13. Did you replace the O2 sensor? I didn't see that in the list of things you did. This is one of the most common problems with these systems.

The EGR will cause rough idle if it is sticking open. If it's stuck closed, fully seated, it will not cause any drivability problems. I preferr mine closed and have inserted a ball bearing in the vacuum hose to the EGR on cars of this era just to make sure it doesn' t pull open. A lot cheaper than buying a new EGR valve.

Tom

 

[Sensei]

.. any thoughts on that new prom? Should I go back to the original?

The Hyperchip is fine. Keep it.

Pulled code and was 13, O2 sensor system.

Your O2 sensor is a critical component in the system, it must be working properly.

Car ran strong for a while then just started being sluggish again on take off; Saturday one time it felt as if when I pushed the gas pedal the engine had no change in rpm.

Is this a general sluggishness with normal acceleration, or does it bog down like it is dying when you floor it?

I am changing ERG, PCV and replacing vacuum hoses as needed. Just mainly for piece of mind to know I have good working parts.

That is all fine. Expensive, but fine. You might want to test things first. A lot of these components really last forever.

One good thing to do if you are motivated (which you seem to be) is to clean all of the system's contacts with Caig Deoxit. You can find it on Ebay:

HOSA CLEANERS LUBRICANTS CAIG-BRAND DEOXIT D5 SPRAY 5oz - eBay (item 130407578522 end time Aug-05-10 12:45:22 PDT)

That is the stuff. The price there seems high, so you might want to look around. The last time I bought it I seem to remember getting 2 cans for around that price, but it has been a while.

Use it on the 4 pin connector for timing at the distributor, on the connectors going into the ECM, the connectors on the carb, etc.

God bless, Sensei

 

[kosbahr]

Sensi,
So what OEM parts should still be connected for optimum performance? I have had an 81 for two years and can not register it due to the CA smog laws that must have a fully operational factory installed emission system. It has failed a smog test once, the car passed the tailpipe test but not the visual inspection. I am up for an exemption by a state referee. What I need is as many original OEM installed parts installed and operational as possible and still pass the tailpipe test. The visual test can be cleared by the referee if the missing parts are found to be unavailable (they have been). If the car does not pass it will be labeled as a "gross polluter" and can never be registered in CA. There are duel cats and duel exhaust with no cross over pipe. What I'm missing is the EFE pipe and check valve from the cat to the smog pump air valve (plugged off at air control valve), the EFE valve pipe and hose from the passinger side pipe heat riser to the thermal valve on the thermostat housing. I have installed a carb from an automatic (have a 4 speed), the correct distributor, EGR soloniod, wire harness, thermal valve and vacuum hoses. Basically what do you suggest to have connected to have the engine run effeciently? Do I need to replace the carb and dist and get away from the ECM system?

Thanks!!!

 

[Sensei]

This should probably be a new thread, but here goes.

No, you do not need to replace the carb/ distributor (it is passing the sniffer test!) The automatic carb is fine. The only difference is that the automatic has a kickdown attachment for the transmission on the throttle linkage.

The AIR pump actually causes pollution, so if it can be deep sixed, so much the better. It was the automaker's way to satisfy government regs they did not have the technology to meet at the time. The regs said exhaust could not have more than a certain % of pollutants. By pumping clean air into the exhaust, it was diluted. This killed fuel economy, causing the car to actually produce more pollutants. They claimed the system worked by causing unburnt fuel in the exhaust to finish combusting. There is a name for when unburnt fuel in the exhaust combusts: backfiring!

Bottom line, without the AIR system functioning, it should pass the sniffer test as long as it is properly tuned and running well.

God bless, Sensei

 

[Tommy Almond]

Sensei, changed out the ERG valve and made a vast improvement on the idle and take off response. Old one was in bad shape and was sticking some so now a new one in place. Thanks for your input and thoughts.
I feel so good about the ole girl now that she was taken to the paint shop yesterday to get the full treatment and a new dark blue paint finish with clear coat to replace the original paint she had. No color change, love the dark blue.

 

[Sensei]

Everybody loves a happy ending!

God bless, Sensei