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Rough idle 1999 Malibu 4 cyl
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Maliboozer
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Dec 13, 2012, 4:36 PM
Post #1 of 14
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Rough idle 1999 Malibu 4 cyl
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Hello.
My car: 1999 Chevy Malibu 2.4L 4 Cyl
My car idles rough (it has for a long time) once it is up to running temperature - it seems to idle fine when it's cold. It has given a "cylinder 2 misfire" fault code numerous times. I've tried changing spark plugs, cleaned and swapped fuel injectors (I was doing work that required removal of the fuel rail), and just recently replaced the #2/3 ignition coil to no avail. It hasn't produced the code again yet, but still idles poorly (I don't care that much except it just failed an emissions test due to high HC ppm at idle...). Any suggestions before I send it to a real mechanic?
Thanks.
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Hammer Time
Ultimate Carjunky
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Dec 13, 2012, 4:43 PM
Post #2 of 14
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Re: Rough idle 1999 Malibu 4 cyl
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You might want to take a complete compression test.
The most common cause of misfire on that engine is the white plastic coil housing and the spark plug boots
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Dec 13, 2012, 4:44 PM)
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Maliboozer
Novice
Dec 13, 2012, 5:09 PM
Post #3 of 14
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Re: Rough idle 1999 Malibu 4 cyl
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D'oh! I was wondering about that plastic thingy. Is that problem due to a bad high voltage connection inside the plastic? I checked the resistance of the connections within the housing, but I didn't know what value I was looking for. After you mentioned the boots, I remembered I did switch #1 and #2, but I don't know which cylinder is now missing since I haven't gotten another fault code.
Is there a way to test the plastic housing or the boots? Should I check for vaccuum leaks and if so, is there an easy way to do so?
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Hammer Time
Ultimate Carjunky
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Dec 13, 2012, 5:12 PM
Post #4 of 14
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Re: Rough idle 1999 Malibu 4 cyl
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The resistance means nothing. That piece acts as a distributor cap on that engine and they crack internally and cause crossfiring. I would just change it and the spark plug boots and make sure none of the plugs have hairline cracks in the glass.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Maliboozer
Novice
Dec 13, 2012, 5:19 PM
Post #5 of 14
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Re: Rough idle 1999 Malibu 4 cyl
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Awesome thanks, I'll give it a try.
As for the compression test, would a simple compression tester be OK, or do you mean a leak-down test?
(This post was edited by Maliboozer on Dec 13, 2012, 5:24 PM)
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Maliboozer
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Dec 13, 2012, 5:26 PM
Post #6 of 14
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Re: Rough idle 1999 Malibu 4 cyl
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BTW I'll let you know how it goes in a few days - the car is in another city and I'm away for work for the next 5 days. Thanks again.
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Hammer Time
Ultimate Carjunky
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Dec 13, 2012, 5:55 PM
Post #7 of 14
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Re: Rough idle 1999 Malibu 4 cyl
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I would probably try the housing and plug boots first and if you still have an issue, take a compression test. Just a basic compression tester will do.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Maliboozer
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Dec 13, 2012, 6:49 PM
Post #8 of 14
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Re: Rough idle 1999 Malibu 4 cyl
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I'll do that. Thanks much.
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Maliboozer
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Dec 19, 2012, 2:48 PM
Post #9 of 14
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Re: Rough idle 1999 Malibu 4 cyl
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OK. I replaced the housing, the boots, and the spark plugs. I also switched the coils, to see if the misfire would move to another cylinder. It still idles rough. Instead of P0302 (cyl 2 misfire), now I get a P0300 (random/multiple cylinder misfire detected). Time for a compression test, or is there another possible culprit somewhere in the ignition system?
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Hammer Time
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Dec 19, 2012, 3:01 PM
Post #10 of 14
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Re: Rough idle 1999 Malibu 4 cyl
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What brand plugs are you using?
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Maliboozer
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Dec 19, 2012, 3:08 PM
Post #11 of 14
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Re: Rough idle 1999 Malibu 4 cyl
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Champion. I checked the gap before I put them in as well.
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Hammer Time
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Dec 19, 2012, 3:50 PM
Post #12 of 14
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Re: Rough idle 1999 Malibu 4 cyl
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You should be using Delco plugs in that car and nothing else.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Maliboozer
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Dec 19, 2012, 4:15 PM
Post #13 of 14
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Re: Rough idle 1999 Malibu 4 cyl
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You really think that could be causing the misfire(s)?
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Hammer Time
Ultimate Carjunky
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Dec 19, 2012, 4:25 PM
Post #14 of 14
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Re: Rough idle 1999 Malibu 4 cyl
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I don't think it's the whole problem but it's likely a contributing factor. You want to check them closely for cracks in the porcelain too. Look for black carbon tracks.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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