Patient: 1989 Corvette Convertible manual transmission.

Problems: Service Engine Soon light on, rough idle and loud clunk during engine braking conditions.

Description: RPM at idle go up and down on a cyclic way, like a wheel spinning with an Off center hub.
The clunks appear when I remove the foot from the throttle and the engine starts the "braking" action, gears on.

Thanks to you guys' knowledge, I was able to run the Trouble Codes.
Result: Code 32 EGR circuit fault and Code 36 Ignition system circuit error or Transaxle shift problem.

Code 32 is self explanatory but for Code 36 which way should I go base on the above sintoms? Ignition or Transaxle?May a worned U-joint be the problem for the clunks and the ignition for code 36?

Anybody had anything like this before and willing to share the corrective actions? Anyhint is highly appreciate and by the way you guys are great. You really know this great cars in and out!

Thank you for your valuable time.

 

I am showing code 36 to be Mass Air Flow Burn Off Circuit. For code32 The most common cause of this code is a bad or intermittent EGR switch which is located on the EGR pipe between the exhaust manifold and the intake manifold. Replace this switch first when you get this code. Next, check electrical connections at EGR valve solenoid and then the ECM. Check all vacuum lines for leaks especially around the EGR valve. Possible ECM failure.

For code 36 Check connections at MAF, MAF relay and MAF Burn off relay. Check resistance of MAF relay and MAF burnoff relay with digital Ohm meter. replace if less than 18 Ohms. Possible ECM failure

 

Dear LeesVette:

Thank you for the reply. I got my codes out of Chilton repair manual. I'll try your valuable suggestions and I'll let you know the results.

Have a nice weekend, mine will be under the hood!!!

 

Use this link and look up the codes and remedies.

http://corvettebuyers.com/c4vettes/ecm.htm

Scroll down, look up the code number and click on that number for possible action.

 

Regarding your loud clunk during engine braking;
Definately check the U joints in the propshaft and in the rear half shafts, but also check the splines where the rear half shafts connect to the rear hubs. Make sure the splines are clean & lubricated, I would suggest anti seize or teflon pipe thread sealant, and make sure the rear hub nuts are properly tightened. Dry splines can make a lot of noise even if the nuts are tight.

 

Back in the olden days, when I was a tech in a Pontiac dealer, we saw a lot of problems with the relays for the MAF sensor & the MAF burn off. I would suggest replacing both the MAF & the MAF burn off relay, as was suggested in a service bulletin for Firebirds with the same engine when code 36 set. If the MAF burn off is operating, if you have the air duct disconnected after the engine has been running for a while then turned off, you can watch the MAF wire glow orange when the burn off relay is on. It is kinda cool to watch!

 

Thanks for the link Lee. AWESOME info

Dave

 

I agree entirely with Leesvette on this one concerning Code 36. I had the screens cut off my MAF 7 years ago and I periodically get a Code 36 reading, but my Corvette mechanic tells me that the code will sometimes pop up because of the increased air flow through the screenless MAF, which is working flawlessly. I certified this finding last year with MECH258, and I believe he cautiously agreed with this. Just make sure your connections to and fromk the MAF are clean and well-connected. Good luck.....

mypetu39