I have a 97 Subaru Impreza. My check engine light was on. I had it plugged in and it said P0301 and P0302 (Cylinders 1 and 2 misfire). I had them do a diagnostic at the shop, and they said I needed new plugs, wires, and possibly a coil. They suggested I do the plugs and wires myself and if it's still misfiring, bring it back in for the coil.
The thing is, I never noticed a misfire. The day after I had it diagnosed, the check engine light turned off. They didn't reset it. Would it reset itself?
2007-11-23 03:56:27 · 4 answers · asked by Anonymous in Cars & Transportation ➔ Maintenance & Repairs
97 is an OBDII (second generation) on-Board diagnostic system. It can detect misfires by using the engine's crankshaft position sensor. If the computer saw an erratic signal from the crankshaft it will set the misfire codes.The computer system did not detect the misfire again so it reset. The misfire codes can be set by rough road surfaces causing a very small change in crankshaft speed, dirt roads, chuck holes, etc, but that is rare. If the light does not come on again you should be OK.
2007-11-23 04:13:47 · answer #1 · answered by Older1 4 · 2⤊ 0⤋
Replace the plugs. It's the cheapest maintenance thing an owner can do other than 3000 mile oil changes and air filter replacements. Misfire codes usually don't reset,they are still stored in the computer memory. It's possible the light might go out if the plug miss is intermittent. I'd change the oil too. When a cylinder misfires the un-burnt gas gets into the engine oil and will dilute it causing bearing failure. Pull the dipstick out and try to light the oil on the end with a lighter. If it burns there's gas in the oil, if not it should be OK.
2007-11-23 04:31:53 · answer #2 · answered by thebax2006 7 · 1⤊ 1⤋
most misfire conditions occur under heavy load or wet weather conditions. Intermittently.
If the computer sees no misfire conditions for a while.....it will turn off the check engine light itself.
A tempermental crankshaft sensor can fool the computer into thinking there is a misfire, by the way. But usually has other symptoms with it.
2007-11-23 04:11:02 · answer #3 · answered by vile_fly 4 · 2⤊ 1⤋
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Check engine light turns itself off?
I have a 97 Subaru Impreza. My check engine light was on. I had it plugged in and it said P0301 and P0302 (Cylinders 1 and 2 misfire). I had them do a diagnostic at the shop, and they said I needed new plugs, wires, and possibly a coil. They suggested I do the plugs and wires myself and if it's...
2015-08-14 17:29:53 · answer #4 · answered by Anonymous · 0⤊ 0⤋
most do not stay on all the time, they go on when you start the car then go out, after starting and stopping a few times, until another problem happens
2007-11-23 04:03:39 · answer #5 · answered by koma 6 · 0⤊ 3⤋