Okay, so my 1991 Camaro RS 3.1 all of the sudden started running extremely rough. About 500 RPM.
I took the EGR valve off today and the car idled around 1200 RPM and sounded smooth.

Before this happened I filled up my gas tank and added a bottle of injector cleaner. Maybe carbon ended up in the EGR valve?
Should I replace it? Thanks for any help anyone can offer.

 

Anyone have any input?

 

I've heard that you can have your car running and give it some throttle and if the egr opens up it's a good egr, but I've also heard that you can push the plunger in when the car is at idle and if nothing happens it's not the egr, if it doesn't open at all well...time for a new egr.

 

Hey thanks for the reply. I ended up breaking my EGR valve yesterday, so I'm going to have to replace it anyway
I could step on the gas and it would run smooth above 2000 RPM, but horrible once it dropped below that.
I'm thinking it must be the EGR. I'll post what happens.

 

Okay, so I replaced my EGR valve today and still have the same problemo!
It will idle at 500 RPM or just stall.
If I hold my foot on the gas it fires up and idles smoothly at higher RPM's, but takes an eternity to climb up in RPM!
It will still run fine with the EGR valve off.

 

Any codes being set? You have a digital EGR controlled by the ECM in three steps. As the ECM demands more EGR, a different solenoid is activated. The 3rd has a large port and can stall the engine. If the Red, light blue or brown wire to the EGR is grounded (with ignition off), the associated port will always be open and can cause a rough idle or a stall. The EGR also uses input from the coolant temp sensor, throttle position sensor and the manifold absolute pressure sensor. Exhaust gas is inert and does not aid in combustion and is what causes the stalling/rough idle. As the RPM increases and draws in more air, it will run better. This is all from the 91 field service manual. It also says the ECM has a built in diagnostic check for the three solenoid EGR valve. When the vehicle is decelearting the valves are normally closed. The ECM then opens each solenoid in order and monitors the manifold pressure for the approrpriate increase. Should the correct pressure not be seen, Code 32 is set.

I would check for grounded wires going to the EGR then check the MAP sensor, TPS and CTS but all the sensors should set a code if failed. MAP is Code 33 or 34, TPS is Code 21 or 22 (and may cause a high idle if failed) and the CTS is code 14 or 15.

Also, did you block off the EGR port while you have it off?

 

Thanks Zig!

Alright, update:
The car will not even run now! Not even rough idle, and not even with the EGR off.
It will start and die. I smelled a lot of fuel! And it had black smoke.

I will try what Zig said, but any thoughts for what's happening now?

 

Okay, one more thing.
Now if I hold my foot all the way down on the gas it will run.
It is super nasty though, the exhaust is popping the whole time you gain in RPM and it hangs at about 4000 RPM before jumping up if you really have your foot in it.

I didn't block the EGR off when I took it off, but now it won't run regardless.

 

Probably fouled the plugs. Pull adn inspect them then clean them. Also block the EGR port if you have it pulled off. That will casue a bad idle in itself.

 

Oh my gosh, I didn't even think of that...
Your probably right. I'll check the plugs.
Thanks for all the help, I'll keep you posted!

 

Okay, the spark plugs were EXTREMELY fouled out!
I sand blasted them and put them back in.
It fired up and ran at a nice, smooth idle for about a minute and then stalled out.
It now won't idle smoothly anymore.

I thought it might need cleaning out, so I fire it up and took it for a drive down the highway.
It stayed running the whole time until I came to a stop, then it would stall.
What to check now... have any ideas?

Also, this must be tranny related, but it would rev up and not shift until I let off the gas?

Thanks.

 

One more update:
I've been smelling a lot of fuel, so figured it was probably running rich.
I pulled off a vacuum hose coming out of the rear of the manifold.
It fired right up and idled nice and smooth just about where it should.
If I put my finger over the hose it would stall.

Now to figure out what is causing this rich mix. Any ideas?

 

It is officially derivable with the vacuum hose off.
Unfortunately the gas mileage sucks because it is running SO rich.

What should I check? Maybe the O2 sensor got carbon coated?
I really don't think it's the fuel injectors, but I haven't tested them.