EGR error disappears
Thread Starter
Heel & Toe
Joined: Feb 2013
Posts: 16
Likes: 0
From: Alabama
EGR error disappears
I recently obtained my first vette, a 1986 Coupe. The only error code that I pulled was the EGR Circuit.
Right after I brought her home I took her to a local business where they would let me put her on the rack and inspect her closely. At that time I used a 3-part fuel injector cleaner http://www.expressoil.com/services/fuel-systems/.
All of the the fuel I have used since I got her back from her former state has been non-ethanol 93 octane.
A few weeks ago I ordered my first batch of parts from Ecklers, and included a EGR sensor in that order after having read to start there on clearing up the EGR Circuit error code (32).
Since I placed that order with Ecklers the error code has not returned. I first noticed that instead of the "Service Engine Soon" light coming on and staying on until I cut the ignition off, it would come on and then five or ten minutes later be back off. Now it seems to just stay off, like its fixed.
So is it possible that the use of quality, non-ethanol gasoline could clear up a EGR code, or is the fuel system cleaner I used more likely the cause?
What do you guys use for fuel in your C4s? Is High Octane fuel good enough, or does it need to be non-ethanol?
Thanks for the input!
Derek
Right after I brought her home I took her to a local business where they would let me put her on the rack and inspect her closely. At that time I used a 3-part fuel injector cleaner http://www.expressoil.com/services/fuel-systems/.
All of the the fuel I have used since I got her back from her former state has been non-ethanol 93 octane.
A few weeks ago I ordered my first batch of parts from Ecklers, and included a EGR sensor in that order after having read to start there on clearing up the EGR Circuit error code (32).
Since I placed that order with Ecklers the error code has not returned. I first noticed that instead of the "Service Engine Soon" light coming on and staying on until I cut the ignition off, it would come on and then five or ten minutes later be back off. Now it seems to just stay off, like its fixed.
So is it possible that the use of quality, non-ethanol gasoline could clear up a EGR code, or is the fuel system cleaner I used more likely the cause?
What do you guys use for fuel in your C4s? Is High Octane fuel good enough, or does it need to be non-ethanol?
Thanks for the input!
Derek
Safety Car
Joined: Oct 2007
Posts: 4,426
Likes: 229
From: Pennsylvania
I had the same problem with the EGR valve code coming on and going off by itself too on my 85. I disconnected the vacuum hose going to the valve and noticed that the metal tube going into the EGR valve was clogged. I took a small drill bit that matched the inner diameter of the tube and drilled it out. I could feel the clog disappear. I then used my hand vacuum pump on the EGR valve to check if the diaphram was still good. It was good. That was more than a year ago, and the problem is corrected. As far as fuel in your 1986, a fuel rated at 89 octane is all that you should need if your engine is completly stock. I tried 87 octane in my 1985 and it pinged. Now I stick with 89 octane. Putting 92 octane in a 1986 stock 350 isn't going to do much except drain your wallet even more with the ridiculous prices of gas today.
Last edited by FOURSPEEDVETTE; Feb 25, 2013 at 09:05 AM.
Le Mans Master
Joined: Jun 2009
Posts: 6,528
Likes: 752
From: South Dakota
You might want to take notice of when the light turns on.
The EGR doesn't function all the time. On my '88 the EGR was bad, but the light would only come on after about 10 miles at highway cruising speed. In town it frequently would not turn on.
Good luck.
The EGR doesn't function all the time. On my '88 the EGR was bad, but the light would only come on after about 10 miles at highway cruising speed. In town it frequently would not turn on.
Good luck.
Safety Car
Joined: Oct 2007
Posts: 4,426
Likes: 229
From: Pennsylvania
That's exactly how mine was acting up.
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
The EGR code is because the ECM doesn't see the EGR working when it turns it on because;
EGR is not actually working
or the switch which tells the ECM the EGR is working is faulty
Could also be a problem with a bad ( intermittent ) wire connection to the terminal on switch (common )
Le Mans Master
Joined: Jun 2009
Posts: 6,528
Likes: 752
From: South Dakota
When I looked into it, the egr code on my '88 was set when that insulated tube at the back of the manifold has a sensor. When the egr is supposed to be functioning, that sensor should show that it is hot from the exhaust passing through it.
There are a few threads on here that say you can "fool" the computer to turn of the light by wiring a resistor into the sensor wiring so it thinks it is hot and it won't trip the code. I tried that a couple of ways, and couldn't get it to work. I finally broke down and just changed the EGR valve. That fixed mine. (Just a note: I tried one from a local parts store and it wouldn't hold a vacuum. I checked the second one before I left the store and it was bad too plus it was the wrong part for some other application in the correct box for what I needed. I got the original AC part and it worked fine.)
Good luck.
Thread Starter
Heel & Toe
Joined: Feb 2013
Posts: 16
Likes: 0
From: Alabama
I am driving about 40 miles of interstate at normal highway speeds each way to & from my job. It's been about 2 weeks of driving it, about 20 hours of driving combined, without seeing the code again.
I think I'll just install that sensor I bought and forget about it if the error code does not return.
All I need to do is unhook the electrical plug and unscrew the sensor? When I install the new one should I use some anti-sieze or something on the threads of the sensor?
Appreciate you guys!
Derek
Safety Car
Joined: Aug 2009
Posts: 3,751
Likes: 276
From: Melbourne, Victoria, Australia
The EGR valve is commanded by the ECM only at cruising speed in varying pulse widths, the ECM then looks at the temp sensor to confirm it is working and will set a code if the temperature sensor is not closed when it should be.
The valve will shut when accelerating or not on a steady cruise hence why it does not give a code in stop start driving with varying throttle positions.
The EGR code will appear after a steady cruise of 10-20 mins if the sensor does not close with the temperature.
Check the EGR tubes are not blocked for later 86 early c4 had the egr bypass in the inlet manifold.
Check the valve actually works, you can do that by sucking on the vacuum hose to the valve and confirm it rises and drops again. Note if it sticks you will get hard starting.....
There is a vacuum solenoid valve that the ECM opperates it has the vacuum hose from the TPI inlet manifold going to it and the other hose on the valve goes to the EGR valve under the tpi manifold but you can see the EGR valve by looking between the runners.
Good luck should be a simple fix
The valve will shut when accelerating or not on a steady cruise hence why it does not give a code in stop start driving with varying throttle positions.
The EGR code will appear after a steady cruise of 10-20 mins if the sensor does not close with the temperature.
Check the EGR tubes are not blocked for later 86 early c4 had the egr bypass in the inlet manifold.
Check the valve actually works, you can do that by sucking on the vacuum hose to the valve and confirm it rises and drops again. Note if it sticks you will get hard starting.....
There is a vacuum solenoid valve that the ECM opperates it has the vacuum hose from the TPI inlet manifold going to it and the other hose on the valve goes to the EGR valve under the tpi manifold but you can see the EGR valve by looking between the runners.
Good luck should be a simple fix
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My 86e would show the SYS lite after crusing at highway speeds for 20 minutes or so.
It would go out and stay off (self clear) until I repeated the above condition.
I replaced the EGR temp sensor that's mounted in the exhaust tube from #8 to the intake.
No more code.
It would go out and stay off (self clear) until I repeated the above condition.
I replaced the EGR temp sensor that's mounted in the exhaust tube from #8 to the intake.
No more code.
Last edited by JrRifleCoach; Feb 25, 2013 at 08:27 PM.
Thread Starter
Heel & Toe
Joined: Feb 2013
Posts: 16
Likes: 0
From: Alabama
My 86e would show the SYS lite after crusing at highway speeds for 20 minutes or so.
It would go out and stay off (self clear) until I repeated the above condition.
I replaced the EGR temp sensor that's mounted in the exhaust tube from #8 to the intake.
No more code.
It would go out and stay off (self clear) until I repeated the above condition.
I replaced the EGR temp sensor that's mounted in the exhaust tube from #8 to the intake.
No more code.
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