Corvette Shuts Off due to EGR Valve No SES Light C4 1985
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- Опубліковано 22 гру 2022
- My 1985 Corvette would stall or shut off occasionally in stop and go traffic or when coming to a stop. There were no fault codes and no Service Engine Soon light. I changed just about everything related and I was about to give up when I read an old post on the web that explained my problem. It ends up that my EGR valve was either stuck open or the diaphragm was leaking. The EGR Valve needs to be closed and not allow any air when decelerating or at idle because if unaccounted air is coming through the intake manifold the gas/fuel air mixture will be thrown off and the computer will not know how to correct the ratio, and the car will stall or shut off. Also, after replacing the EGR valve and swapping the EGR Temperature Sensing Switch, I made the mistake of screwing it all the way in, causing the switch to be closed all of the time. This caused a SES light during a cold start. The SES light would not come on during a warm or hot engine start. The fix was to back out the EGR Temp Switch about two threads verifying with a meter that it was no longer closed.
A couple of more things not mentioned in the video is that the EGR Solenoid Activation Valve may be causing the EGR Valve to remain open. If your car continues to stall or idle rough after replacing the EGR Valve, verify that the EGR Valve Actuator Solenoid is operating properly. Also, a large source of a vacuum leak can be from a cracked or leaking Brake Booster. A smoke check for vacuum leaks does not always catch it. Consider replacing it if your brake pedal pressure seems unnormal. I hope this video helps.
Below is a link to a really good Corvette EGR article that explains everything about the EGR including how it works and how to test it etc…
tech.corvettecentral.com/2012...
That's good information to know, probably solved a million 85 Corvette owners' headaches. I now know, thanks, Juan.
You’re welcome Johnny. I have to give credit to the Corvette forums and articles where people write about their troubleshooting experiences.
The C4s are really good solid cars and they are fun to drive. The C4s are definitely a bargain treasure.
I have a 90 that was truly painful ruff idle issue. The intake had an oil leak at the back of the manifold. So, since it was apart, changed out the egr, which was nasty. Idac value, thermostat, O2 sensor was ok. After all that the car would show a cede 32 after it got warm. Turns out the Y fitting was cracked going to the EGR vacuum sensor. Other idem was a bad EGR from Delco. wouldn't hold Vac. So even new parts should be checked before install. Had a smoke check done and found the leak. You wouldn't have seen that, and leaks can be sneaky suckers. Runs good now. Thanks for your sharing your 85. I know the Vac. routing is different with a 90, but sometimes the simple stuff can happen.
Absolutely, I agree that the simple fundamentals can fool you. These are phenomena of physics which can be corrected albeit once discovered. Thank you for sharing as well!
WOW!!! BEEN CHASING THIS PROBLEM FOR OVER A YEAR. ONE OF MY VETTE CLUB MEMBERS CAR HAD THIS ,COULD NOT GET A STATE INSPECTION. I SEARCHED MANY C4 VETTE & THIRD GEN GM CARS FOURM. I HAVE MANY FACTORY C4 MANUALS & DID NOT EVER RUN ACCROSS THIS POSSIBLE FIX. BEST, I WILL GET HER CAR BACK IN MY SHOP ASAP, THANKS A MILL.☑🗝
Yeah, this was a tricky one!
My 89 is doing exactly the same thing and I got a code 32. I’m going to replace the EGR. Thanks!
Hey Albert, let us know how your repair turned out. My C4 runs like a champ now and no more stalling or shutting off. Remember that a vacuum leak can throw off the gas fuel mixture ratio and it can cause your car to stall or shut off when decelerating to a stop. Another hard to detect vacuum leak source is the brake booster. They have been known to crack or the diaphragm will leak when they get old. Good luck and enjoy your classic Corvette!
The EGR was clogged and rusted shut. I replaced it but unfortunately my C4 still stalls. I’m going to replace the fuel pump now. Fingers crossed. Thanks Juan!
Another thing to consider replacing is the often overlooked IAC (idle air control valv). It’s not to expensive.
Also, you could have a bad fuel injector. Check the resistance of each one and it should be around 26 to 28 Ohms.
Another few items to consider are the Fuel Regulator Valve, the MAS ( Mas Air Flow Sensor), and the TPS (Throttle Positioning Sensor).
And maybe a clogged fuel filter?
What is the history behind the car?
Hi Juan, I replaced the fuel pump and still turned off. It idles rough after it warms us so I’ll now change the IAC. Thanks for that suggestion.
You can do an EGR delete. However, it requires programming a custom chip for the computer.
I have a similar problem. not necessarily stalling in traffic although it has happened. mine will stall simply when idling and warming up while in park too. it doesn't just stall though, it will lope and rev up and down almost like it has a huge cam in it. each time the rpm drops, the check engine light flashes, then the light turns off when the rpms rise, and the cycle repeats until the engine stalls. the check engine light turns off once it stalls, and no code gets stored. this only happens when its below about 65 degrees F outside. I have a hunch it has something to do with the egr but im not sure.
It could possibly be related to your Mass Air Flow sensor, because the air flowing into and through the MAF affects the computer’s calculations of fuel and ignition firing, and the temperature of the air flow can affect the millivolt output of the MAF. Another possibility is the IAC valve (Idle Air Control Valve) at idle it should throttle to control the air/fuel ratio so that the engine idles properly.
Also, have your vacuum lines/system smoke checked for vacuum leaks because air coming in unaccounted for will throw off your gas/fuel mixture when idling. Driving down the road it won’t be noticeable because you are burning more fuel etc…
@@JuanLopez-nt1dh since I made that comment, the problem has actually fixed itself. I deduced that the stall would only happen during the first start of the day, and only when it was below about 65°F outside. I’m not totally sure, but I think it may have had something to do with the EGR valve getting stuck when it was cold and on the first start of the day, and then freeing up afterwards. Not sure though. Never looked into it again after the problem stopped on its own.
Maybe the car just needed to be run for a while until something became unstuck or burned itself clean? The intermittent problems are the hardest to fix, unless you can duplicate the problem?