94 Ford Expedition Emissions Problem


#1

I have a 94 Ford Expedition. Recently, I had emission problems. The car would unexpectedly jerk while driving. The “check engine” light came on. I replaced the catalytic converters. The “check engine” light is no longer on. However, the car is still jerking while driving. It feels like hitting a speed bump: a short “thump-thump” and loss of power, then it drives normally again. Any ideas? Does this sound like the O2 sensors are going out?


#2

I meant a 2004 Ford Expedition. Sorry.


#3

Why did you replace the catalytic converters? The symptoms you describe have nothing to do with the cat.

I don’t know what’s causing this problem, but I’ll bet money it has nothing to do with the catalytic converters. Your experience backs me up.

No, it does not sound like the O2 sensors are going out.

Bad O2 sensors do not cause "bucking"or “jerking.” They just cause the CEL to come on.

Please explain the cat replacement. What were the codes when the CEL came on?


#4

First step is scan the vehicle for any possible codes. AutoZone, Checkers, etc. will do this for you free. Post any results back here for discussion.

Converters and O2s will not cause the symptoms you describe. Wild guessing a bit here with no info, my feeling is that it’s a fuel pump hiccup caused by a failing pump or an ignition fault; coil(s), crank sensor, MAF sensor, etc, etc. etc.

When was the last time the fuel filter changed; if ever?


#5

The “jerks” are engine misfires. A dirty fuel filter, dirty air filter, and fouled spark plugs will cause misfire. After that, what are the results?