99 Explorer 4.0/OHV Stumble during acceration

[grayghost]

99 Explorer 4. 0/OHV 125k mi. The problem initially began as a misfire or stumble only when accelerating while climbing a hill, it's progressed to a definite misfire and stumble during acceleration at all times. Runs smooth at idle and cruising. Plugs & wires are fairly new.

My guess is that it's not ignition unless coil, crank sensor.

Could this be caused by something in the injection/air intake system?

Any help appreciated

Pete

 

[my98nnj]

A misfire under load is usually ignition related. You may have a failing/weak coil.

 

[Yankee516]

Can you also remove and clean your MAF sensor with cleaner? Had a major hesitation and lack of highway power. Once I cleaned it REALLY good with the special spray, problem gone! Just don't touch anything to the sensor itself other than the spray of liquid, and let it air dry for a while.

 

[swetrid]

Double ck number 4 and 5 plug wires, they get burned thru from improper routing.

 

[shoalcreek5]

Replace the PCV valve. It should be replaced every other oil change any way. It's only 3 bucks at autozone. If it's clogged, it can cause the engine to stumble sharply under load. It will also get worse the longer it goes. Let it go too long after it gets clogged and you'll do some serious damage. Also, the PCM might never set a code with a bad PCV--my OHV didn't ever set a code last time I had to change one early.

 

[grayghost]

Thanks for the suggestions

Cleaned MAF tonight (MAF makes a hell of a humming noise at times??)

Put an inductive timing light on all wires, one clearly displayed an eratic flash (misfire) thinking maybe coil since plugs & wires may be OK. Thinking about replacing all three?