My car misfires often, and abruptly, on the highway. It will misfire about 9 times in 10 seconds. Some of these are fairly jolting on the car, and sometimes it feels like the car has stopped accelerating all together for a few seconds. I have been playing around with it while driving in the last couple weeks and this is what I have found:
1. I can replicate the symptoms (misfiring) in all gears but symptoms are the worst in the higher gears.
2. If I shift early, keeping the rpm's down, the car seems to do much better, not missing as much. And when it does, it doesn't jarr the car too much.
3. On the highway going normal speeds (60-75mph) the car will misfire less if under heavy acceleration (flooring it) and misfire even more under slow deceleration (slowly letting back on the pedal). The car really bucks when peaking a hill and easing a tad off the pedal. However, if I *quickly* get off the pedal it seems to decelerate okay without the car bucking too much.
4. Symptoms are present when the engine is hot or cold.
5. The car is definitely running rich, the mileage is terrible and I've even seen a couples flames shooting out the tailpipe when it misfires on the highway real bad.
6. I thought it was fuel starvation so I replaced the in-tank pump, the outer in-line pump, and the fuel filter.
7. After that I thought it might be spark so I put in a new ignition coil, cap, and rotor. (All 3 pretty much due for replacement). I looked at each spark plug and wire and they all looked pretty good but fairly black from running rich. Dropped in a new air filter at this time as well.
Nothing has solved this so far. Any ideas??
1. I can replicate the symptoms (misfiring) in all gears but symptoms are the worst in the higher gears.
2. If I shift early, keeping the rpm's down, the car seems to do much better, not missing as much. And when it does, it doesn't jarr the car too much.
3. On the highway going normal speeds (60-75mph) the car will misfire less if under heavy acceleration (flooring it) and misfire even more under slow deceleration (slowly letting back on the pedal). The car really bucks when peaking a hill and easing a tad off the pedal. However, if I *quickly* get off the pedal it seems to decelerate okay without the car bucking too much.
4. Symptoms are present when the engine is hot or cold.
5. The car is definitely running rich, the mileage is terrible and I've even seen a couples flames shooting out the tailpipe when it misfires on the highway real bad.
6. I thought it was fuel starvation so I replaced the in-tank pump, the outer in-line pump, and the fuel filter.
7. After that I thought it might be spark so I put in a new ignition coil, cap, and rotor. (All 3 pretty much due for replacement). I looked at each spark plug and wire and they all looked pretty good but fairly black from running rich. Dropped in a new air filter at this time as well.
Nothing has solved this so far. Any ideas??
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