EGR ?

[ak diesel driver]

Working on a 94 k2500. It idles and runs rough, fuel system checks out ok. Tried a known good PMD didn't seem to make any difference. Checked the codes and there was 8 of them, 3 EGR 3 Trans, 1 turbo, and one stepper motor. Haven't checked the vac system out yet other than it doesn't roll coal. It's pretty hard starting, warm or cold and may be just glows. Any way my EGR ? is how do you go about testing if it is working properly? when should there be vacuum at the EGR valve and how much should there be? I assume it will be varied by the ECM. I'm triying to rule things out before I go to injectors and/or IP. Most of the smoke I do get is white and is definetly unburnt fuel

 

[3500GMC]

The hard start shouldn't tie into egr I wouldn't think. My vote is for stepper motor.

 

[turbovanman]

EGR should only get vacuum when the computer commands it, which is at cruise, its off at idle and WOT. Testing it, the rpm should change if you apply vacuum at idle, if it doesn't, then the valve is faulty or its leaking internally.

 

[tanman_2006]

Egr delete will fix atleast 3 codes.

Is timing ok? My 95 has a stepper motor issue and my truck cranks about 3 times warm or in warm weather but it starts better in the winter w/ cold fuel. Been mid 40's the past few mornings and it cracks off in 1.5 revs. Also has 60k on accurate injectors and atleast 3 leak down (3 chugs then smooths out)

Source Unknown

 

[Twisted Steel Performance]

I would think you could plug the vac line going to the egr and see if it changes anything....

 

[WarWagon]

I am not 100% sure the 6.5 EGR operates like this. Some EGR valves are 'regulated' by backpressure. So the vacuum is on or off and the EGR opens with backpressure. There is a complicated valve in the EGR valve that controls it's opening. If you apply vacuum at idle and the valve flops wide open it is bad. Ours may operate differently.

 

[Twisted Steel Performance]

Me either WW, I haven't messed with ours, I tried to edit the post, but too much time had passed... :mad2:

 

[tanman_2006]

I took mine off and did a F swap. I might still have the valve, it's been bout 5 yrs ago though.

Source Unknown

 

[uniquediesel]

May not be a stepper motor actual fault either, if it's out of the time range (not timed correctly), it'll set this fault.

 

[ak diesel driver]

So update. We finally got down to it had to be the IP. So I had a good 5068 pump laying around and my brother installed it. Didn't run much better, he said it ran better initially. So he brought it over for me to time. After he got here it started running like crap. Wouldn't idle acted like the throttle was dead. I set the idle to 800 and managed to sorta set the timing. Still ran like crap. So finally I decided to unplug the CPS, it took a long time to start but idled perfectly. So my next ? is why didn't it show any counts missed on gmtdscan software?

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