I had a problem the other nite with my `87 305 IROC 700R4. Off the line, you hit the gas, and the car would NOT go! if you very easily gave it gas, it would accellerate, but barely! If you floored it, it sounded like the car had a Mack truck engine break. Now, I have tested my EGR valve per everything I have read in the Haynes manual, and AllDataPro. It works fine! With these EGR valves being a back-pressure operated EGR system, I know they are a bit tricky to test! Could it be possible that the EGR is intermittently faulty!? I had the plenum & fuel rail off yesterday, flow testing the injectors - which one of them looked like you were turning a water faucet on and off, so I got that taken care of. Now my idle is 99.9% better, but the car still seems to be running a bit rich in closed loop. Could it be that there's a a faulty EGR, but it's not all the way bad that the tests will show!?

 

Instead of typing everything over, please read this thread on my stumbling problem. The EGR was what caused the problem. Acted just like yours. You could accellerate easily, but the second you gave it gas it bogged. Also, be sure and get a GM EGR valve and sensor. Do not get an aftermarket one. Do a search on EGR valves and you will see what I mean about aftermarket valves.

Dan

https://www.thirdgen.org/techbb2/sho...hreadid=129411

 

I actually noticed that after I posted this, and couldn't delete it and redo it!

Is there a such thing, though, as an intermittently faulty EGR valvE?!

 

Could be an intermittant EGR solinoid or one that sticks and has the valve open all the time.

 

Thinking about it, my problem was intermitent. I drove to UPS one day and on the way back some ***** honda pulled up next to me and goaded me into a stop light to stop light run. Thankfully it ran great and I easily beat him. Then pulling away from the next light it stumbled again. So yes they can be intermitent. At least that was my experience.

Dan

 

Would it be an intermittent solenoid or valve, though! I guess it wouldn't hurt to change both, huh!?

After I pulled the fuel rail off, and flow tested and cleaned the crap out of the injectors, the idle is 99.9% better than it has been since I have had the car. The only problem now, is it is still running way rich, which I guess a bad / faulty EGR would possibly do, correct!?

My stumbling problem is for the most part, 99.9% gone! The only problem that I have right now, is a hunting idle at a stop light, or traffic or whatever. Most of the time, when pulling upto the stop light, if I pull up slow enough, it doesn't hunt, or it minorly hunts, like 100-250rpm or so. If I stop fast enough, or sometimes, even sitting there for a period of time, it will idle fine, then start hunting for about 5 seconds, upto like 400RPM, enough to launch the car if I didn't have good brakes. Then othertimes, 75% of the time, it hunts right when I come to a stop, then settles down after about 5 seconds, right where it should be. And if you really pay attention, while driving, at like between 2000 & 3000 rpm, right where the EGR really kicks in, it sometimes slightly chokes back. not enough to hear it, but enough that the driver can feel it. But nowhere near as bad as it was when I first got the car!

This could all, in fact, be a bad / faulty EGR, correct!? I have changed every other thing that could be changed. O2, MAF, Air filters, fuel filter, checked the pressure for both vacuum and fuel, cleaned the injectors, etc. this could be the only thing left, that I would imagine! Any other thoughts!?

 

Well an EGR from GM (you should always use the factory EGR) costs between $50-$80 (can't remember exactly) and I have no idea on the solinoid.

Here is a simple test for the EGR valve though.

Take a small inspection mirror and place it under the valve so you can see the bellows, next remove the vacuum line to it and hook up a vacuum pump (Mityvac works great and has hundreds of uses on a car), next pump the vacuum pump and watch the bellows, it should move upward and stay there until you release the vacuum going to it. If it doesn't stay retracted until released or if it sticks open after it is released, replace the valve.

The solinoid is a bit harder to troubleshoot, it is controlled by the ECM and could either be actuating uncommanded or the ECM is telling it to open when it shouldn't.
I would tend to think it is just carboned up bad and sticking open. On a V-8 it is harder to diagnose than a 4 or 6, if they stick open then the engine will die at idle within a minute or so when at operating temps.

 

I've already tried that Morley.. I read that test for the EGR valve somewhere on here before, so I did it, and it worked. I found a test for the solenoid in my Haynes manual, and it also worked fine! So that's why I am saying.. Is it still possible that the tests that they give you to do with the car not operating can cause the EGR system not to undergo as much strain and stress, and to pass the tests, but fail when under a real load!? I think I said that right!

--- Charles!

 

Well, if everything passed the static tests then that points to the ECM possibly giving the command to open the EGR when it shouldn't be. Have you tried disconnecting the plug from the solinoid and driving the car to see if the problem is still there?

If the valve passed the static test then it is good, it is a simple open/close valve and just responds to the vacuum applied by the solinoid.