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Rough running 1990 Legacy
Posted 23 April 2004 - 11:52 AM
The car idles really rough (shakes the car). It has good power when accelerating hard, but if driving along around 2000 rpm, it starts to buck as if there is crossfire. It feels like it is going to die, but a sligh increase in throttle and speed eliminates the problem.
The plugs and wires were replaced by the previous owner just before I bought the car. The check engine light has not come on since I have had the car, but the records indicate that some sensors have been replaced in the past. The O2 sensor appears to be original. I could not detect any vacuum leaks in the engine and the PCV valve is fine.
A couple of other possible clues - The car had overheated in the past, due to thermostat problems and the radiator leak. All the plugs were clean, but one plug did have a much darler insulator than the rest.
Any tips are appreciated.
Posted 23 April 2004 - 05:31 PM
Posted 23 April 2004 - 06:04 PM
Posted 23 April 2004 - 08:59 PM
Well, I had ruled out a blown head gasket because the antifreeze is just antifeeze and the oil is just oil. It also does not make any funny noises that I have come to associate with head gasket failure in other cars.
I had considered a burned valve, but was hoping to hear that burned valves never occur. The fact that one plug was dark could lend credance to a burned valve. I guess I'll try a compression test - I suspect it wont show up unless it is really bad.
I guess neither option is particularly pleasant. Does the engine need to be removed from the car to pull a head? Also, are the blocks still prone to stripping threads? The last head I pulled was on an 84 Gl and I ended up having to put inserts in the block after the threads pulled out when removing the head bolts.
Posted 23 April 2004 - 10:05 PM
I'll post any additional findings in my other thread.
My shaking car rough idle started on a damp day just like a shorted sensor or something but I have done/checked a lot (listed in thread) but have not fixed it yet.
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