avgjoe

I recently changed the intake manifold gasket on my totally stock 88. While I had it apart I replaced the EGR temperature sensor because the wire to it was broken. At that time the engine light would come on with code 32 (EGR) when I was out on the highway for a while and I assumed it was because of the broken wire. Now, since I did the intake and replaced the temp sensor, the engine light comes on upon startup and stays on until the water temp reaches 160 and then it goes off. I still get the light when on the highway for a while and it stays on until I turn the car off. The only code I have is code 32 which is EGR. The FSM gives a very detailed flow chart on diagnosing that code. Just wondering if anyone has any ideas for me since I don't have a working scan tool.

I have checked to be sure everything is hooked up properly. I also replaced the EGR valve itself a couple of years ago when I first got the code when driving down the highway and it made no difference.

Thanks for your help.

billschroeder5842

When you replaced the EGR did you check the tube to see if it was clogged? If the EGR was faulty, the pipe could have clogged it. Also the O2 sensor could be tricking your EGR

ctmccloskey

Did you verify that you EGR systems Vacuum solenoid is working properly? It is attached to the thermostat housing by one of the two nuts. Does it have a good connection electrically and a good source of vacuum? The ECM use PWM to control the solenoid so don't expect a solid signal testing it.

I also have a 1988 L98 C4 Coupe and when my EGR failed it did not set off any lights or warnings. My short pipe section near the thermo switch got way hotter than normal and started to burn off the velcro reflective covering.

I found out I had an EGR problem when I went to get the emissions tested and got a higher than normal NOX reading. There was a lot of carbon in my passageways so I had to remove the intake to de-carbonize it completely.

Good Luck! Driving a Corvette in Virginia is great isn't it!

Best regards,

Chris

avgjoe

This seems like a place to start and it makes sense that I could have done something to cause this when I had it apart for the intake gasket change. I'll check that first. It seems I may have two different conditions going on.

avgjoe

Yes, driving a Vette in Virginia is fantastic. It loves the mountains I have checked and cleaned the electrical connection at the solenoid. Any suggestions on how to check it's functionality?

Thanks!

avgjoe

I didn't check the tube. I will do that. I can see that a clogged tube could be causing the light to come on when on the highway.

ctmccloskey

Hello again avgjoe!

The wire going to the sensor on my car had the insulation falling off of it due to the heat they get exposed to. Ihatebarkingdogs sounds like he knows what he is talking about so that would be the first thing I would look for. The wire can get grounded very easily in that area but can be very hot so do it while it is cool. Disconnect the wire to the EGR's thermo sensor and test it to see if in fact if it is grounded without being connected to the sensor. If it is than that would be the problem.

On my 1988 I tested the EGR with a vacuum pump to see it move and you will hear some change in the engine when it is opened manually. When mine failed the carbon built up on the parts prevented the movement of the diaphragm. The vacuum solenoid applies vacuum to the EGR when told to do so by the ECM. Measuring the power is a bit harder as it uses PWM to control the EGR and like a lot of things it probably has 12 Volts at one side when the car is turned on and the ground is applied when the ECM wants the EGR to operate. The ECM likes to apply Ground (0 Vdc) to make things like injectors fire so it would be similar I assume. Let me look in my manuals and see if there is a procedure. Using my Snap On MT 2500 I can make the EGR go through a self test which tells you right away if it is working properly.

Do you go to Corvettes@Carlisle at all? It is right up I-81 in Pennsylvania. It is 103 miles from my door to their entrance of the fairgrounds. It is the third weekend of August and is a blast if you have never been to it. I might be taking my C3 there this year as it fun to drive.

There is one book I highly recommend to ANYONE who has a C4 Corvette. It is called: "How to Understand, Service and Modify CORVETTE FUEL INJECTION & Electronic Engine management" and it was written by Charles D. Probst and printed by Bentley Publishers. This is one book that really helps me understand the various components of the fuel systems. It is a good book to have in addition to the factory service manuals.
This book covers all the systems used between 1982 up to 2001 and the following engines are covered: L83, L98, LT1, LT4, LS1, LS6 and ZR-1

Enjoy those beautiful Mountains!
Chris