The past few days when I start my truck the RPM's have been going all over the place and I can feel the whole truck shaking just sitting in park. I've been watching my Gryphon and the RPM's bounce anywhere from 20-90RPM's without touching the gas. The motor will even run rough higher into the RPM's too so it's not just at idle. I had the spark plugs changed about a month ago and the fuel filter has also been changed recently so I'm not to sure what the deal is. I also haven't had any codes come up lately either.
Sorry, I meant it would change up and down anywhere from 20-90 RPM's. So anywhere from 610-700RPMs is where I'm idleing at.
BTW it will do this when I start it and the next time I start it it will be fine and then it will be bad again for a few starts and magically it will be fine for a start or two.
i'd still clean the maf. and does it matter if the engines cold or warm at startup? does it get better as it warms up? you have a cai? and what brand plugs did you use?
Last edited by Matts ford; 11-05-2009 at 03:10 PM.
Cleaning the throttle body smoothed out my idle and stopped the RPM stumbing prior to the cleaning. In fact, it's probably due for another cleaning soon.
Remove the air cleaner and use a good, clean rag that's damp with WD-40. Clean the TB and butterfly valve as best you can. You will be surprised at the amount of buildup you can get out of there. My next plan is to remove it and bench clean it but who's got time for that?!?
Good luck.
I took the throttle body off last night and the thing was damn near spotless. It must ave been cleaned when I took it in and got the spark plugs changed. I have still yet to figure out if it gets better as the truck warms up but I should figure that out today. Are there any other simple things I can check or do that might help the problem?
My aem isn't an oil filter aothat shouldn't cause problems and I cleaned the mas while I cleaned the throttle body.
When I was driving tonight it was really rough until the motor got warmed up until 145 degrees or so then it ran perfectly fine. I have no idea what's going on.
Try disconnecting the battery for several minutes. Let the computer reboot/relearn. Sounds like a throttle controller problem though. Might need a reflash or the controller is bad.
Just thought of something - it could very likely be deposits on the back of the intake valves from using fuel with inadequate additives. I'd take it to a shop that has a BG or Motorvac machine and get an intake cleaning job done.
Reason it runs rough till it warms up is this - until it reaches operating temperature, it's running a default fuel map. The deposits are screwing up the mixture due to flow disruption. When it's warm and in closed loop, the O2 sensors are compensating for the deposits.
You can try using a Techron fuel additive, but by the time deposits cause rough running, it's usually too late for it to work.
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2003 F150XL 4.2 short cab/bed 4x2 5 speed manual 3.55 LS
I try to avoid crappy gas stations that you would imagine have ****ty gas. I went and got two bottles of Techron for the hell of it today and put them in. Could it be any coincidence that I poured a bottle of seafoam in my last tank, and the same tank I have noticed problems on?
It's possible the Seafoam fouled the spark plugs. What brand of gas do you usually use?
You were asked what brand plugs is in there - and I don't see an answer. That can be critical on these engines - they really don't like much of anything else but stock Motorcraft. I hope you don't have to pull them - it's a PITA on the 5.4 3v's.
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2003 F150XL 4.2 short cab/bed 4x2 5 speed manual 3.55 LS
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