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Discussion Starter · #1 ·
got a 89 suburban with the 5.7 tbi and it will every once in a while want to begin surging at about 30-35 mph with a steady throttle and will also sometimes try to die at an idle after stopping, you can give it some gas and it will idle up and clear up?? the idle also seems to change slightly at times?? it is not calling out any codes and I have replaced pluggs, cap, rotor, wires, 02 sens, tps, fuel filt, and the idle air control valve and has not seemed to make any diff, not sure what to try next??
 

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Could be a sticking EGR valve. Is this actually in a Burb, or in your CJ?

If it's in your CJ, I presume you are not running the tranny it came with. You might want to get a custom chip, as I think the 89's computer controlled the tranny.

It could also be a leaking MAP vacuum line - this seems to be the most likely issue. Or a leaking at the TB and/or intakes manifold/runners to the head - my friends 94 had this problem.

If all checks out - you might want to get a WINALDL and a laptop and see what the computer sees.... This gives you an on-board real-time diagnostics. For more info you can check out www.thirdgen.org this site is dedicated to the F-body, but they have WAY more info than you ever wanted to know about GM ECMs.

Finally, it could be a bad TPS, (has a bare spot in it), or a going bad temperature sensor.

The temperature sensor would be hard to check, but the TPS, you can get a DVOM and check for consistently growing resistance as you sweep the throttle. If it suddenly goes open, than that's your culprit.

Good luck.
 

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TopOff said:
Could be a sticking EGR valve. Is this actually in a Burb, or in your CJ?

If it's in your CJ, I presume you are not running the tranny it came with. You might want to get a custom chip, as I think the 89's computer controlled the tranny.
'89 computer controlled the lockup converter only, on 700R4s. IIRC, on 400s, it controlled the kickdown.

Pete
 

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Discussion Starter · #5 ·
it is still in the burb and I have already changed the tps, but this morning it did come up with the tps low output code?? but I am not sure if it was stored from when I was messing around unhooking stuff? It seems to run great otherwise, I should be able to see a vac leak with a gauge shouldn't I?? I had a guy run a scanner on it while it was running and it came up with the tps low output so that is why I changed it, but it didn't fix, I tried to do the tps calibration but got stumped at the retracting the idle air control motor plunger? but the output of the tps is in the range called for in the book with a closed throttle....I did notice that the inside of the distributor is kind of rusty? so I cleaned it up with some electrical spray but again did not help
 

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I've had the same problem on my 89 Chevy Cavalier, and it could be the mass air flow sensor or you may just need to replace the computer. Good luck!
 
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