Backfiring at highway speeds

[pebrown]

Ok Guys, I have one for you. My 91 XLT, is missing and backfiring approaching hiway speeds. It runs like a top in town. Starts great, and idles fine. I've cleaned the air flow sensor, and reset the engine computer. Also in cold weather, the speedo measures about 10mph faster from time to time. Has anyone run into these problems?

Thanks,

Pat B.

 

[mrboyle]

Not sure about the speedo, but the backfire sounds like a lean miss. Try changing the fuel filter, if this doesn't fix the problem your next step is to have the fuel pressure tested.

 

[oahrens]

Could be the FPR...but you would probably notice the MPG loss and bogging at all times. Chk Eng Lght would also come on.
I would look towards a clogged cat. Have you ever replaced any exhaust parts?

 

[pebrown]

Hey, my problem seemed to have solved itself. Must have been bad tank of fuel. I filled up, no more problems. Runs like a top. Go figure.

 

[jimmiecakes]

After a bad tank of gas is an ideal time to change the filter.... no telling what might be trapped in there now.