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P0304 Check Engine problem


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7 replies to this topic

#1 vixen220

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Posted 26 August 2003 - 09:48 AM

I have a 99 Legacy OB Wagon with manual transmission. About 6 months ago, it started running rough when the RPMs dropped below 2K in any given gear. It was skipping/missing/bucking on acceleration from stops and from just slowing down.

My mechanic could find nothing wrong, even though he could reproduce the problem.

FINALLY, it had the problem Friday, and the "Check Engine" light came on. My mechanic said it was a P0304 error, and that SOA was recommending a complete replacement of plugs, coil, and wires. However, my mechanic says he has another customer with the exact same symptoms, and this complete replacement did not fix the problem.

Any advice, comments, suggestions?

Thank you,

Vicki

#2 theotherskip

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Posted 26 August 2003 - 10:29 AM

the code is for a misfire of the #4 cylinder. changing the plugs & wires would be the first thing to check before doing further diagnotics. he should be able to check them before replacing them, though, especially the coil.

#3 incognito

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Posted 26 August 2003 - 11:37 AM

Not to be a wongleflute about it... but...

thats a misfire... start replacing stuff. Start at plugs. If you replace them, and the same (#4 = drivers-rear cyl) fouls the BRAND NEW plug, its before the plug, chances are its just a plug wire. If not, have fun.

For some reason, platinum plugs work like crap too. Put a good 'ol set of NGK's in there if you haven't already.

Good luck, ive been fighting a #4 cyl misfire on a EJ25 for a year now.

I have a certain gasket problem that occured when my car was wrecked by the previous owner.

BTW, this post looks normal now *edited part* TO ME *end of edited part*, but im a lil :drunk: right now. Disregard anything offensive :banana:

#4 ferret

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Posted 26 August 2003 - 01:35 PM

Fuel Injectors can also cause misfires. After plugs/wires, try the injector. Swap it with another one. These are the most common causes. But it can also be the Coil, Cam sensor, Crank sensor, ECU. I have seen all the above cause misfires on various vehicles.

#5 vixen220

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Posted 26 August 2003 - 02:19 PM

Hi folks!

Thanks for the info.

I've found I can make the CE light go on if I replicate the conditions of the first time it went on.

I.e., if I "baby" the hesitation by backing off the gas and downshifting to boost the RPMs, the CE light stays off. If I "bull" the hesitation by tromping on the gas (no worry about acceleration, since the car is practically dying...heaven help me if I try this trick and the engine doesn't continue to misfire...) the car hesitates even more, runs rough, coughs, sputters, bucks, and generally acts very sick, THEN the CE light comes on.

I just got the CE light again, and I'm taking back to the mechanic for another code read and reset...

Thanks again,

Vicki

#6 bulsi

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Posted 26 August 2003 - 08:09 PM

I don't know if this would generate a misfire code, but my '98 OB had similar symtoms and it was the Mass Air Flow sensor.
I was well past the standard warranty expiration, but got it fixed under the Emissions Control warranty, which is a bit longer.
Anyway, for what it's worth, something else to consider.

#7 incognito

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Posted 27 August 2003 - 10:48 AM

I.e., if I "baby" the hesitation by backing off the gas and downshifting to boost the RPMs, the CE light stays off. If I "bull" the hesitation by tromping on the gas (no worry about acceleration, since the car is practically dying...heaven help me if I try this trick and the engine doesn't continue to misfire...) the car hesitates even more, runs rough, coughs, sputters, bucks, and generally acts very sick, THEN the CE light comes on.




Plug wires. Plug wires. Plug wires.

You have the EXACT, and I MEAN EXACT!!! same symptoms I had before this happend:

http://usmb.ultimate...=&threadid=2818

BTW: it was my #4 cylinder too :banghead:

#8 vixen220

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Posted 27 August 2003 - 11:46 AM

Again--thanks for the feedback and validation!

I went to my mechanic on the way home from work, and it was the #4 cylinder again.

Weird thing is, we changed the plug wires back in October as part of its 90K checkup. The car wasn't hesitating then...the hesitation started back in February/March. It got a new timing belt in June, when we discovered it hadn't been done when it was supposed to have gotten done.

Anyway, my mechanic told me to make the CE light come on one more time, just to be sure it's *always* the #4 cylinder, and then we'll fix it. I'll make the CE light come on when I'm heading home tonight, now that I know I can do it whenever I want to.

V




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