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88 GMC K2500 Stalling Problem

it will run with the aldl grounded. this puts the system in back-up spark and fuel mode. base timing and no fuel trim available.

  1. Am I suppose to start the truck? All I did was turn the ignition on. Tim No, do NOT start the truck with the ALDL port grounded! A few more questions...............
1) Will it do this forever (start, stall) or does it eventually resolve and let you get moving? 2) When you tweak the skinny pedal, in neutral, do the revs come up smoothly or is it sluggish/rough 3) Manifold vacuum (in/hg) at idle in neutral? Manifold vacuum at 42 would blink 4 fast, pause a moment and then blink 2 times. The sequence will begin and end with a 12. Each code repeats itself 3 times 2004 15:07:43 -0500, "Tim Duerst" wrote: :|> :|> >:|Hi, :|>=A0>:| :|>=A0>:| :|> >:|First, a little history- Last summer I had to replace the fuel pump in :|the :|> >:|tank.... not fun, but not too bad. I also replaced the fuel filter. It :|has :|> >:|been running good until this week. It starts ok and idles fine for a :|TBI 350 :|> >:|engine. I can rev it and it's fine but, when I put it in gear it goes :|> >:|forward and then stalls. It starts right up again and stalls the same :|way. :|> >:|My question is this related to last years pump replacement or something :|new? :|>=A0>:| :|> >:|Thanks, :|> >:|Tim :|>=A0>:| :|> :|> do you have any DTC? :|> -Bret :|
Reply to
pete carb
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Ummmm... grounding the ALDL with the engine running puts the system in "Field service mode," fixed timing above base and the CE light indicates open or closed loop and rich/lean status. Jumpering pins "A" and "B" with a 3900 ohm resistor will put the system in back-up spark and fuel mode.

Reply to
Neil Nelson

Ok, I took the vacuum at idle and at 3000 rpm it stays steady at 18. I did replace the egr valve. The other one was froze up. Still does the same thing. The funny thing is that I can go farther in reverse than forward. Any more suggestions would be helpful.

Reply to
Tim Duerst

Ok, the purpose of the vacuum test was to look for vacuum leaks and also a plugged catalytic convertor. From what you have posted, neither of those are the case.

Have you tried upping the revs to maybe 1300-1400 RPM and then dropping it into gear to see if the same thing happens (not too good for tranny, don't try this more than a few times).

Have you tried jacking up the rear-end, supporting it on jackstands, and putting it into drive to see if you can duplicate the effect with no load on the engine?

Another thought, try putting it into1st instead of "D" and see if the same thing happens.

Sounds like a funky electrical connection in your steering column. If it happens while she's up on jackstands this would further that "guess."

Doc

Reply to
"Doc"

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