I have no check engine light on and have around 170,000 miles. My fuel pump was supposedly replaced 8 months ago when I bought the truck. I have had one coil and spark plug replaced in order to pass smog. Now when accelerating it feels as though its losing power and begins to shake. I do know that I need a new timing belt but can anything else be causing the shaking. I dont want to blindly go to a mechanic and be screwed over.
Loses power while accelerating and shakes on 1999 Ford Expedition
by effintruck in Moreno Valley, CA on October 22, 2010
ANSWER by DaveJM on October 22, 2010
Starting from the end, this truck has no timing belt. It has chains. So you will not need to be servicing that area. Losing power and shaking - with 170,000 miles and evidence of replacing another coil and plug, I would lean towards suggesting they all be changed, with new boots on the coils. If you can have the vehicle tested, a power balance test can tell you which cylinder(s) may be the culprit if you have a misfire. This is where I would start. Otherwise, you may have an issue with an injector, or some other area. But the plug/coil issues are so common that I lean towards that.
ANSWER by Visitor on February 27, 2011
I HAD THE SAME PROBLEM WITH MY 99 EXPY 4.6 LITTER. THE LOOSE POWER AND SHAKING TURN OUT TO BE THE IAT VALVE IT IS LOCATED ON TOP OF THE TROTTLE BODY. YOU MIGH WANT TO TRY THAT FIRST GOOD LUCK GEORGE.
ANSWER by Visitor on February 28, 2011
we ended up doinh, full tune up and replacing the mass air flow sensor. The misfire was in cylinder 3 the timing belt I thought needed replacing is actually A serpentine belt I think was the name