350 Tbi Egr?

I also posted this in the GMC forum..But I figured the Cheby forum would be more active.


Great Site!!
My 125k mi. '87 GMC Shortbox 1500 350TBI 700R A.C. stumbles at cruising or at low throttle input(10-25%)

I've repaced cap,rotor,fuel filter and problem still occurs.(I'll do plugs next)
I've had the truck parked for a while , but the problem was starting before I parked it.

I did discover though when I disc. EGR the problem goes away.
If I roll the throttle up from idle the engine wants to die.

Under a load the truck seems fine

With my hand on the EGR , I can feel it moving , and when I diconnect it at that time , the engine comes back to smooth running.

The EGR valve seems to hold (blowing through it)
The EGR sol. seems to shut down on decel.

Am I close? or looking in the wrong area

sounds to me like you found your problem.If you disconect the egr and it fixes the problem more and likely thats it.Remenber the egr valve opens at crusing speeds.It should not open at idle and if it does the engine will idle rough stumble and possibly die out.if iwas you i would remove the egr valve get a vacuum pump and test it .Also look if the egr is not restricted with carbon deposits and the passage way itself.If you find any restriction clean it because it might be keep the egr valve from opening and closing all the way.

sounds to me like you found your problem.If you disconect the egr and it fixes the problem more and likely thats it.Remenber the egr valve opens at crusing speeds.It should not open at idle and if it does the engine will idle rough stumble and possibly die out.if iwas you i would remove the egr valve get a vacuum pump and test it .Also look if the egr is not restricted with carbon deposits and the passage way itself.If you find any restriction clean it because it might be keep the egr valve from opening and closing all the way.

I'm sorry ...I should have been more clear.
I can feel it moving when throttle is applied. It stumbles in that low throttle range but at 25% on up it seems to be ok.
If I duplicate the stumble at low throttle and I unplug the EGR the engine recovers quickly.
That's where I left it.
Thanks for your input.

Did you vacuum test the solenoid? It needs to hold a vacuum on the TBI side.

//2000CAYukon

Did you vacuum test the solenoid? It needs to hold a vacuum on the TBI side.

//2000CAYukon

I didn't put a gauge on it...but it seems to hold.

At Idle it seems fine , it's at partial throttle that dogs the engine out.

I've heard the EGR could be weak and moving too much/feeding too much...haven't had time to dig into lately.

Will probably r&r EGR (from what I'm hearing):banghead:

I didn't put a gauge on it...but it seems to hold.

At Idle it seems fine , it's at partial throttle that dogs the engine out.

I've heard the EGR could be weak and moving too much/feeding too much...haven't had time to dig into lately.

Will probably r&r EGR (from what I'm hearing):banghead:

went to several repair shops and had numerous scans and $2000 parts and labor.

turns out 4 year old egr was sticking intermittently causing many trouble codes and issues.
replace egr!