Engine Performance problem
2001 Ford Taurus 6 cyl Front Wheel Drive Automatic 120000 miles
My car is running rough at idle (drops low like it wants to stall) and also at highway speeds (stumbles). Only code is cylinder 2 misfire. The problem seems intermintent.
I replaced the plugs and wires, I hadn't done it in a while, it needed it, but they didnt look too bad. That didnt work. I replaced the No. 2 fuel injector, that didnt work. I replaced the vaccum lines, but that didnt do anything. It has a coil pack, all 6 on one, so my thinking is, if it was the coil pack, the misfire would atleast be random.
On another note, the low coolant light is on, but there is no coolant loss, and it is pressurized. I think its just a bad sensor, because I had a line break a couple months back, lost coolant, overheated, and when I fixed it, its been on since. That may be about the time the problem started, but I dont know. Also, I ran a vaccum test, and it pulls a solid 22-in steady at idle. No flucutation that would indicate a valve or cylinder problem. I am stumped. Any ideas?
Have you checked the firing of that particular plug with it not in the engine? Disconnect all the other wires at the coil pack so the engine does not start and note the spark luminosity if there is one at all. How did it look when you took it out the first time you noticed you had a prblem? Was the compression ok in that cylinder? What was it? Not sure how exactly you recieved an unwavering steady needle on your vacuum guage. It is possible that the missfire happens on every other cylinder fire or even less often or randomly.
June, 24, 2008 AT 8:28 PM
I checked the spark, it seems fine. I didnt check compression, but the vaccum test led me to think its ok. It was " pretty steady", 22 in, plus or minus 1 in, but not the 3-4 in that I would expect with a valve or compression problem. Sometimes it works fine. Other times, it misfires a lot.
June, 24, 2008 AT 8:55 PM
A slightly wavering needle would indicate a slight timing issue. If it is idling rough then there is no way you could have a steady needle (that is why it would idle rought because of poor vacuum). Does it occur when the engine is only hot? You should have two temperature sensors, one for the computer and another for the guage. If you only have one then you might want to consider replacing it. If you can tell me what your vacuum guage does while you experience the rough idle then that would be more helpful. Try removing and cleaning your EGR valve with a small amount of solvent (any alcohol substance will due) a toothbrush and compressed air if you can. Make sure the valve dosent stick.
June, 25, 2008 AT 6:04 PM
It was working fine when I did the vaccum test, hence the no fluctuation. I pulled the EGR valve, it looked clean, and open with vaccum, and shut without it. I ruled it out because the problem happens at speed too, not just idle. I think an EGR valve stuck wouldnt affect it at speed, only idle.
Is there a way to test the fuel injection wireing harness, to make sure the FI is getting the right signal?
I was thinking temp too. I belive the elec. Timing retards when it is low to correct, maybe it is doing that by mistake.
Because it is only showing as one cylinder, I am thinking it must be something with that cylinder.
June, 28, 2008 AT 1:13 PM
You have replaced everything except for the coil pack. It is possible you have a slight vacuum leak right above that cylinder on the intake manifold. You really should check the compression on that cylinder. It is possible a hydraulic lifter(s) to that cylinder are frozen and the valve is not opening and closing properly.