I am a college student and one of our class projects is a 99 dodge dakota with a 3.9l in it. It was donated to us from a guy who has pretty much done everything to it. It has short headers, hughes performance throttle body, msd 6al box, msd coil and msd 8.5 mm wires. It has crower 1.7 roller rockers, with a pretty big cam. (Not sure on specs of cam so i will just say its very healthy) Our problem is after installing all these parts then engine will start and run but only at off idle, also at off idle it has about 3" hg of vaccum when it should be closer to 17" hg. The truck seems to have a timing problem but the timing is controled by the computer so we cant adjust. We are going to scan the PCM and see if the cam sync inside the cap is set propper. Is there anything else we should try doing to get this truck to run. Our goal is to have it up and running by May 9th.

The problem may be very simple, I had the same symptom on my 2000 dakota 5.9 after the battery was disconnected for a while, which caused the SBEC to lose the EFI calibration. You can wait for it to reset on its own which can take a few hours of driving, or use a diagnostic computer to force a throttle calibration. Well at least I hope this is the cause of your problem!

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06 Jeep SRT8

idealrides> Hey, we just replaced the tranny on my sons '99 Dakota, and it will not idle correctly either, dies when coming up to a stop sign. I remember reading something like you mentioned, but I dont remember what I did in the past to help the computer "relearn" so to speak. I have been doing some searching but havent came up with anything. I know I didnt use a diagnostic computer to fix the problem, but cant remember what I did. Any ideas?
thanks,
coadman