82 Vette--Check Engine Light HELP

[Makogary]

I have an intermitten problem with my "check engine light" ,Sometimes it works and sometimes it don't..The bulb and socket are ok. When I turn the key on when its working it lights, When its not working it dos not light. And I am not sure if its affecting the Open/Close loop. It seems to run a little rich and ruff when its not working.. Can anyone tell me how you know if it's in open or closed loop?? Also if anybody had this problem (Check engine light) (On/off) and what caused it..Again all connections are good and are tight, and bulb and socket are ok... Do I have this correct? When you turn on the ignition it tells computor to turn on the light (Check bulb) until you hit start.After that its off until a malfunction occurs.:confused

 

[Hib Halverson]

The service manual has instructions as to what to do if the MIL is not working or intermittantly working on key-up.

As for closed/open loop, back in the "prehistoric" era of engine controls, systems were very slow. In fact, the 81-85 systems are benchmarked with a sun-dial. Things happen very slowly. Also, because the cat and the O2S were so far back inthe system, closed loop sometimes doesn't come at all at idle. The engine usually needs to be fully warmed up and running at an rpm that's off idle for the system to go closed loop.

Once you get your MIL fixed, you can put the ECM in the field test mode and the MIL will flash a sequence that will tell you whether the engine is in closed or open loop. That sequence and how to get the MIL to display it is in the service manual.

 

[Makogary]

82 Vette "Check engine light" HELP

Hib: Thanks for quick response. I have read all manuals I have and can't find anything...Can you point me in the right direction for the "Service Manual" You speak of..MAKOGARY

 

[wishuwerehere82]

MAKOGARY,

Here is a very helpful forum on Crossfire Corvettes. I have found them to be very useful in diagnosing problems with my '82 Vette. The tutorial on Crossfire ECM interactions and the schematic diagrams can be found there.

http://www.crossfire.homeip.net/

 

[Hib Halverson]

Hib: Thanks for quick response. I have read all manuals I have and can't find anything...Can you point me in the right direction for the "Service Manual" You speak of..MAKOGARY

Section 6E of the 1982 Corvette Shop Manual.

 

[jdp6000]

Section 6E of the 1982 Corvette Shop Manual.

Hib,

Finally someone familiar with section 6E.

I am trying to follow the test instruction in section 6E for Code 22. I'm stuck...

I just replaced the TPS. I adjusted it to .525. I get code 22.

In the instruction is states, "disconnect TPS and jumper CKTS 416 and 452". What does this mean???

Does it want me to run a jumper on circuits 416 and 452 (from plug to TPS)???

Any help would be appreciated.

Jim

 

[wishuwerehere82]

Circuit 452 is the black(top) wire on the TPS connector.

Circuit 416 is the grey(bottom) wire on the TPS connector.

Since the sensor is new, Check the connections at the ECM.
Thay may not be making good connection. The ECM is in front of the battery and has 2 connectors plugged in to it.
Those connections are card edge connectors that plug into the ECM boards, and are prone to oxidation. If you pull the ECM out, and remove the case screws, the card edges can be cleaned with a pencil eraser and the connectors can be cleaned with a spray can of contact cleaner.
The connection is a solid wire from the TPS sensor to the ECM card edge connector, so if you don't have a signal it could be a bad connection or a broken wire.

 

[jdp6000]

Circuit 452 is the black(top) wire on the TPS connector.

Circuit 416 is the grey(bottom) wire on the TPS connector.

Since the sensor is new, Check the connections at the ECM.
Thay may not be making good connection. The ECM is in front of the battery and has 2 connectors plugged in to it.
Those connections are card edge connectors that plug into the ECM boards, and are prone to oxidation. If you pull the ECM out, and remove the case screws, the card edges can be cleaned with a pencil eraser and the connectors can be cleaned with a spray can of contact cleaner.
The connection is a solid wire from the TPS sensor to the ECM card edge connector, so if you don't have a signal it could be a bad connection or a broken wire.

To test these two wires am I suppose to run jumpers from ckts 416 and 452 between the TPS and plug??....start the car and wait for the engine light to signal???

 

[wishuwerehere82]

I don't know. I don't have that manual.

What I do know is that the voltage between the bottom wire(grey) and the middle wire(blue) should be set for .525V at idle(650RPM) or not running with the key on, and 4.5 Volts at Wide open throttle. That sets the initial voltages for the ECM to read in open loop mode.
Code 22 indicates that TPS voltage is low, meaning that the initial voltage is too low for the ECM to implement fuel/air mixture calculations.
Back to you, Hib!

 

[jdp6000]

I don't know. I don't have that manual.

What I do know is that the voltage between the bottom wire(grey) and the middle wire(blue) should be set for .525V at idle(650RPM) or not running with the key on, and 4.5 Volts at Wide open throttle. That sets the initial voltages for the ECM to read in open loop mode.
Code 22 indicates that TPS voltage is low, meaning that the initial voltage is too low for the ECM to implement fuel/air mixture calculations.
Back to you, Hib!

I had posted on corvettedoctor.com. The guy over there indicates my book is wrong. The TPS setting for an 82 should be .420 to .460 NOT .525. Have you heard anything similar. I reset the TPS at .420 and am no longer getting code 22. Car runs like crap but it always did so I'm not sure if the cause is the TPS setting or other problems. I'm going to make a manometer today and try to set the TBI's.

Jim

 

[wishuwerehere82]

Yes, I have heard that number before, but was told it was incorrect. It will probably work at any number below .530V will turn off the EGR and set the parameters to idle. Mine also works a little better at a lower voltage than .525V as the mixture is a little leaner.

When you make your manometer, make sure you have a pinhole flow restrictor in the top of the manometer where you attach it to your vaccuum port. It's very easy to exceed 6" of water by setting the throttle plate too wide, and you will end up sucking all of the water out of the manometer into the carb. I know, I have done it.

A standard vacuum gauge that reads in inches of mercury, will work to get you in the neighborhood of 6" of water. 6" of Water is 1/2" of Mercury. You will know when you get them closely balanced, because the cylinders will smoooth out as you approach the balance point. The amount of variance between balance and out of balance is about 1/8 of a turn of the balance screw. It's real tricky to get it stable, especially if your throttle shafts are worn( and who's aren't). Don't rev the engine with the manometer connected, it will suck the water out of it.
But DO operate the throttle with the engine warmed up and the manometer dis-connected, and then recheck the settings to make sure the balance is still correct.
Good luck!