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Im having trouble with my truck running smooth consistantly. I have had it tested and no codes come up. Cleaned MAF sensor, installed new fuel filter and ran a tank of fuel system/injector cleaner and problem is still there, though not all the time. Each time I tried something it would run perfect for a short while then slowly start studdering, sort of like its running out of gas. Im open to any and all suggestions.

 

I have a 98 and here are things I've done to it at various times when it's been running poorly:

• Replace the PCV valve - small but significant
• Check that the vacuum hoses are not leaking
• Check that electrical connectors to the throttle body accessories and sensors are connected (although I think you would get codes if they were not)
• Clean the IAC valve
• Clean the throttle body and all its ports thoroughly (requires removing the throttle body)
• Replace the front O2 sensors (I've been told that the rear ones have nothing to do with how it runs, but only measure the performance of the the cats.)
• Make sure the Intake Manifold Runner Valve can move freely (this required removing the intake... on the 98 4.6) - mine was semi-stuck at one time.

This is what comes to mind this morning (before I've had any coffee).

Anybody else care to weigh in?

 

How many miles on it? When were the plugs and cop's last replaced if at all?

 

Im not sure, bought the truck 3 months ago and ran fine til about a week ago. may be the original plugs thats my next move and the truck has 130k