1999 Ford Explorer Misfiring above 50mph

jilyjo · Posted at Tue Nov 03, 2009 7:20 pm

Engine Performance problem
1999 Ford Explorer 6 cyl Four Wheel Drive Automatic 143000 miles

I have a 99 Ford Explorer that was working perfectly fine until I had a transmission service done: Trans filter, Fuel Filter & Trans Fluid replaced. Right after, I notice it is misfiring when I'm accelerating above 50mph. It also runs very rough at 60-70 mph. This is intermittent. Sometimes it's fine and sometimes it's not. Took it back to the shop who did the service, they said tests came back with nothing. Took it to the Ford dealer hoping to get better answers. They just told me what I already know... it is misfiring. They suggest replacing spark plugs, wires, coil for $900. I'm weary about doing that since I think something during the original service created this problem. Any suggestions before I replace these items?

Jacobandnickolas · Posted at Tue Nov 10, 2009 8:59 pm

I would start b checking fuel pump pressure. Something tells me there is a problem there that MAY have been caused when the filter was replaced.

Here is a how to:

http://www.2carpros.com/how_to/how_to_check_fuel_pressure.htm

Also, I think it is crazy to replace all of the coils. Many people do it because they don't know which may be causing the problem. It's an expensive experiment that may or may not fix the problem. If there is a miss, the computer should tell them which cylender is missing. If it is random and a multi cylender misfire, then it's usually fuel related.

Let me know what you find or if you have other questions.

Joe