Hey everyone, I was curious if someone has ever had this problem and what they've done to fix it. In the last two weeks, whenever I start my truck in the morning, it goes up to 1900rpms and then down to 400rpms or so and then back up and down and up and down and, well, you get the point. Once I start driving, it doesn't do it to badly, but it then goes from 700rpms to 400rpms and then again and again and again. No check engine light on or gauges freaking out. It's like the computer cant stay steady. I live in FL with 91 degree days and afternoon showers. Driving to and from school today, it did it again. I don't know if it's hurting anything, but I like my stuff running right. I will deeply appreciate any help given. Please tell me this isn't a stealership problem. Thanks.

 

is it a 4.7 and what year

 

2002 4.7L Auto.

 

Try resetting the ECM. That seems to fix a lot of weird stuff that happens... at least it has for me. Pull fuse 19 from the fuse box under the hood, buckle the seat belt, close the door, turn the key to "run" but don't start it, wait 10 seconds or so and it will chime twice. Turn the key to off, replace the fuse and then see what it does.

 

kinda sounds like a vacume leak but with the way computers control things these days who knows

 

Yeah, vacuum leak or a bad temp or manifold air pressure sensor...(or intermittant connection).

 

i agree to check to vaccum first but their is a TSB out for low idle when in drive that requires a flash at the dealer [&o] when i called to see how much mine was going to be it was 100bucks to re-flash it with the new system, sorry for the bad news

 

My 2001 Dodge Stratus R/T was doing the same low idle thing. It kept getting worse until it finally would start dying when in neutral. The shop is telling me it's a bad AIS motor ($730). I'm looking into it now.

 

first thing came to mind was IAS. had a nissan sentra that did the same exact thing. lucky i had a spare engine laying around cause they are expensive.

 

vac line.....