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I just got my truck back on the road and am having this problem. Every time i start it, the idle goes up to 2500 sits there for a few seconds then slowly comes down to about 700. I'm sure the computer hasn't fully "learned" the truck but i still don't think it should be doing this. also when i put it in gear it wants to idle high, and when i pop it in neutral coming out of drive or reverse the rpms go up to 2000 then drop past 500. are idle relearns really this bad? mods are in sig.
You didn't mention which mods were just done, but it sounds like you could have a vacuum leak. To verify, unplug the MAF and start the engine. If the surging stops and the idle becomes less erratic, you have a vacuum leak. Any codes being thrown?
How long has the tune been in? These don't have a specific idle learn procedure. +1 on possible vacuum leak and/or IAC problem if DWC.
Just about all the mods in my sig were done, 6.0 swap, cam, tune (2002 pcm), trans, exhaust. I did unplug the maf, started it and it did the same thing. i also double checked the tightness of my intake bolts. I'm going to swap on a stock throttle body with different sensors and spray it down with some carb cleaner and see where that gets me.
oh yea, it's not throwing any codes yet
Update: Today i fired it up in the morning and it idled at 1500 for a few seconds then came down to 750. went to get gas and when i started it at the gas station it did the usual climb to 2500 and come back down. this is after swapping on a different throttle body with different sensors. so i came home and unplugged the MAF, IAC, AIR, CC, took off the air filter, checked the fuel pressure and it still did the same thing. I also put a few miles on it after leaving the gas station and in drive the idle fluctuates from 1100 to 1400. I'm beginning to think there might be a problem in the tune. :help:
There are some tables in the tune that are "Idle Relearn" tables that need to be altered a little to help idle learn faster , at least in EFILive there are .
If done correctly idle will learn within a few miles or starts .
There is a article about cams that is titled "Start once then die" , good read .
Another update, everytime i start it the idle does the usual 2500 then down to 750 and idles high in drive. well i decided to drive it any way and after sitting at a light for about 30 secs the idle went down to 800 and stayed there and it drove great up until i shut it off and started it back up. it then just repeated this process. I think it's come down to an intake leak or the computer not "remembering" the parameters.
Turns out that the tune i got from Nelson had the IAC valve hanging open too long. He sent me a retune, adjusted to make the IAC valve closer faster, and now it idles fine... well a little low sometimes, but it's good
Glad to hear you got it fixed.