When i first start up in the morning, my truck idles at 1100 rpm. After a few seconds, the idle drops dramatically. Had a vacuum leak, I think i've cured that. Note: This happens when cold, however, the idle is still very slightly erratic when warmed.


H E L P

 

H E L P!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

doorslammer69

When cold they start like that. Mine does the same. It's kind of a two step warm up since after going down from around 1100 to around 700 it will get lower around 600 or 500 when warmer. Remember I am reading from the stock tach and usually they have an error. So, this readings are approximated.

Regarding the rough idle, mine is OK now, may be lots of things. What about your check engine light? No messages? Good luck in your search.

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My Ride: 1998 F150 4x4 Lariat Supercab Flareside 5.4L in Oxford White/gold, ORP, Tow Package, 3.55 Gears.

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Had the same problem and fixed it by:

Disconnect the positive wire on battery and turn headlights on for 15 minutes.
(this resets the computer)
Clean MAF.
Reconnect everything.

Should work!

 

High idle when cold starting is normal. Don't worry about that.

Rough idle while engine is hot is quite another. Lots of reasons for it. Just do a search in this forum on Rough Idle.

 

Forgot to mention another fix for the rough idle. I do a lot of slow speed short trips. Not the best kind of driving for an engine. Eventually, I notice the idle getting a bit rough, power drops off a bit, max rpm drops to around 4,800, and gas mileage goes down.

At that point, I take it out on the highway and do 2 or more pedal to the metal runs, letting the engine max out at first. By the second or third run, the engine winds up to 5,000 rpm. I find that I can actually get it up to 5,200 rpm if I really try.

Anyway, the engine starts running silky smooth again, power level is back to normal, and gas mileage goes up.

I don't quite understand why this helps in my case. I'm thinking maybe with all the slow speed short cycle driving, the computer keeps trying to make my engine run super lean. I'm just guessing.

 

Rough idle is not the problem I'm having. I'll be sitting at a light & all of a sudden, the idle will jump up 2-300 rpm, & then drop back down. SOMEONE PLEASE HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

See my new post in the Computer chip section under "Premium gas". SOMEONE PLEASE HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

S O N E O N E P L E A S E H E L P!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

slammer
I'd put a vacum gauge on it & be sure I got it fixed. Mine is running great at 60K so I don't know what else to suggest.

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97 Lariet-sc-4.6-4x off road-auto-3.55 LS-
superchip-K&N-3"
pvc air box mod-Granetelli MAF