Not sure what's up here. My '97 5.4L cranks up, idles normal and runs strong. But after driving only 5 to 10 miles in varying traffic it idles like crap. Stopped with it in gear does the same thing. Rpm's don't seem to jump around or drop. But the truck shakes bad and the engine "sounds" as if its going to shut off, kind of like the rpm's drop too low -but they don't. Even try giving it a little more gas up to @ 1000 rpm and it feels and sounds the same. I haven't gotten a check engine light yet so I wasn't sure where to start. I've already had my injectors cleaned, changed my oil and put on a new fuel filter. Any ideas? I'm debating on sparkplugs, but would they act up only when the engine is warm?

 

How many miles on the plugs? I don't buy the whole "100,000 miles" on these plugs. Maybe in a perfect world, but not in everyday driving these days.

I changed mine the first chance I had after buying it. That was at 62k. The plugs "looked" ok, but had huge gaps on them. Way over the spec.

I put some +4's in, and really only noticed the difference between old and new plugs, but there was a difference. Starts much easier and runs great. I didn't have the bad idle before or after. Just didn't think spark plugs should have 62k on them........

 

MitchF150- only have 49,000 miles and it started about 2,000 miles ago. It does seem to have gotten worse. When I first noticed it I could go a week or two before it happened again. Now it seems to be every time I drive. I do think short trips-like to work(5 miles) are worse than long drives. I've had a Hypertech chip in since new, I think I'll pull it out first and be prepared to get scanned if I need to.

 

Yeah, short trips are harder on an engine then long ones. I'd rather have a high mileage "Highway miles" rig over a low mileage "City miles" rig.

You should be able to pull at least one of the front plugs to at least check it out. If it looks ok AND the gap is OK, then your plugs are probably not the problem.

Only 5 miles to work? That's a great commute, but unfortunatually, your engine is probably not reached operating temp by that time, then is shut down. That's hard on a motor. Not a whole lot you can do, other then drive around the block a couple times

I'm lucky, in that I'm 20 miles to work and 15 of it is highway. Only takes 30 minutes to get to work on average. Hate the traffic however! but my motor and other moving parts, including the exhaust system all has a chance to reach operating temp and function at it's peak. It's amazing how much condensation will collect in the exhaust system if it's not run very long.

Good Luck