Stumble at idle when you first start up (2000 Chevy)

[jeffro788]

Hey guys, I am having a little issue with the truck not wanting to idle at first when you start it up and put it in gear. You have to pedal it to keep it running, but it will eventually straighten itself out and run perfect. It only happens right after you start it and put it in gear.
We have changed the fuel pump, pressure regulator, air filter, and checked the plugs. The idle air control has been checked and operates and all other sensors seem to check out. This happens whether it is hot or cold.
Just a little history on the motor (not stock at all), it is a LS1 (5.3L) lower end with 6.0L (317 stamped) heads, mild cam, whipple supercharger, bigger injecters, custom tune, headers, and 4" y-pipe with a Borla race muffler.
The transmission has a 3000 stall torque converter so I don't think the load is pulling it down.
Not sure if I am missing anything to check. It does run fine after a minute but not understanding what is going on.

[clinebarger]

Did you do any wiring on the IAC curcuit for the blower install? Make sure the IAC curcuits are not wired backward.

[jeffro788]

I don't think there was any wiring done on it. I am starting to believe however that the gas was the problem. It is set up to run on 93 octane and we have ran some regular and midgrade. It seems to be better since there is a full tank of premium in it. I don't know that it has completely solved the problem, but I am open to any more checks I need to make.

[G&R's57GMC]

If your Mass Air Flow sensor has around 100,000 miles OR your using a oiled type air filter

The MAF may be contaminated thus not sending the correct values to the ECM and this will cause an issue like this. The cure is to replace the MAF.

Also 100,000 mile before CAT O2 sensors could be slow acting and add to other problems. Replace them also.

[jeffro788]

I may try the MAF replacing and the IAC also. The O2 sensors are not hooked up and taken out of the tune.

[usmcchevy]

If you have no o2's than you have a SD tune which dosent use the maf, just the iat sensor which is in the maf. You can check its operation with a decent code reader.
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EDIT: Just to add a little more info for you. Google SD tunes, Some people complain about idle quality so your problem may be in the tune. Do you know who did the tune?

[jeffro788]

I do know the peron the person that tuned it, however he worked on it for a little bit and told us to bring it back after vacation, so we took it to some mechanics that we trust and have worked on everything we own that we couldn't do ourselves, they checked all sensors and any codes and they claim it is in the tune, but they are unable to do any tuning. Well, the tuner got off vacation and heard that someone thought it was in his tune and he got his panties in a wad and told us to take it b/c there is nothing he can do for it and it definitely wasn't in the tune according to him. We have found out more and more that some of these guys that tune these motors have pretty major egos and paranoia issues. He claims that my computer is unlocked and I really don't think that it is. If we do anything else we will probably have to buy a new ECM and start over.
Sorry to go on about this...... been a rough time dealing with it.

[truckdude239]

tell him to detune the computer and put it back to factory specs

[jeffro788]

unfortunately my motor probably wouldn't start or get me back home if that was done

[usmcchevy]

A 0411 pcm should be $50-100 at a yard. I'd buy one and find a new tuner.
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[jeffro788]

That's probably the right idea
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