About a month ago my 93 started lurching at low RPM's and partial throttle. It's not the 3k hesitation, as it seems to disappear right about at 3k RPM's (maybe an issue only with the pimary injectors?). Sometimes its pretty severe. It seems to happen mostly when the car has been off for a while, like last time after I went to a movie and it sat outside for about 3 hrs. I've searched in here and elsewhere for a solution, but...

An ECU reset seems to make it go away for a bit, but it comes back. I had disappearing coolant, but I'm almost positive it just needed a new AST cap, as that seems to have fixed it. I'm getting a DP, and I plan to bang out the main cat to make sure there are no clogs this weekend. My grounds are all pretty good, and I have nearly completely gotten rid of the 3k issue. I think I will try and change out the fuel filter this week too.

One thing that might be a clue is a very recent smog check:

RPM....%CO2....%O2....HC....CO%

732.......11.5.......4.9....13......0.00
2379......9.5........7.8.....5.......0.00

It seems that the %O2 is way higher than smog results for other FD's I've seen on here. Even though my problem seems intermittent, could I be running lean all the time? That makes me nervous. If so, could this be caused by a really bad filter? I believe the one in there is about 20k miles old, but I am known for seeing how far I can go with the fuel light on.

Is this result normal for a nearly all stock FD with about 25k on the engine and turbos?

 

i had lurching problems in my car @ low rpms also. Mine was caused by a bad o2 sensor, after a $20 fix, everything is fine again.

 

same problem with my montego 93, i think, i upgraded to 4 guage grounds all around and fixed it. the engine was also burning coolant badly. good luck

 

Does %8 O2 mean the problem is not enough fuel? Anyone?

 

The only real way to tell if you are running lean or rich, is to use a wideband O2 sensor and then check out the A/F ratio.

You can also take a look at your spark plugs, those are good indicators as well.