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Old 06-28-2010, 07:00 PM   #1
rad
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Join Date: Jun 2010
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Default p0304 # 4 cylinder misfire, help please!


hi everyone new to the site and new to saturns in general, im helping out a friend who bought his daughter a 2000 saturn sl 2, 1.9 4cyl with auto transaxle, 180k miles on it! the car came to me with multiple issues and codes, p0131,,p1133,p0713,p0442,,p0304,.. i was able to repair all codes except the p0304 misfire! when my friend bought the car he said there was no check engine light on! the next day his daughter said there was a light on so he asked me if i could look at it. he told me that the previous owner just had it tuned up about 3 months ago, and they didnt drive the car much since then!

here's what ive done so far, checked codes as mentioned above, found that only 4 out of 9 monitors were in the ready status! ive replaced both the upstream and downstream o2 sensors, confirmed that the plugs and wires were replaced,{ plugs were autolite double platinum, which seem to be a no,no, from posts that ive allready read} checked wires and coils for resistance and were in spec! compression check highest 175, lowest 160, i figured not to bad considering 180k mileage! replaced trans temp sensor,, fuel cap, and seen that someone changed the ect sensor and connector! confirmed ect is working correctly with scanner tool! vaccum on this motor is 16 hg at hot idle! ive also changed the oil and trans fluids and filters and used some injector cleaner in 3\4 tank of fresh fuel!!

at this point ive burned pretty much all the fuel out of it on multiple test drives! all 9 monitors are now checking in\ ready status, and only code i have is the p0304 with mil light on! i have noticed that the iac motor has been sticking sometimes so i cleaned the throttle body on engine and found that the underside of throtle plate was thick with sludge, after the cleaning i havent had any fast idle issues as of yet but i believe that i should pull off throttle body and give it a more through cleaning! ive checked for vacuum leaks and found none on external engine not to say there cant be an internal leak,

as far as fuel system the filter looks like its been changed, i have some readings on my scan tool as far as short term and long term fuel trim but i dont know what is normal and what would be considered a problem! im not a mechanic just a do it yourself! so im still learning how ti interprett the numbers, so any help would be greatly appreciated!!

sorry for such a long post but i thought the more info i could provide would be of help to anyone that can help! im new to my scanner and trying to learn it! i can tell ya that the scanner is repoting the p0304 code at idle in park no load!! and i can post what engine conditions were at,, of time of misfire, using the freeze frame and record mode, i have it saved! thanks for any and all advice in advance!!! the car has to pass emissions in my town!! thanks again!!

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Old 07-01-2010, 02:39 AM   #2
iwish98
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Join Date: Jun 2009
Location: Buffalo,MN
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Well this is a compression sense waste spark ignition system: one coil fires two plugs simeltaneously one on compression one on exhaust so one would believe you have spark....have you checked the injectors one may short or go open i believe the resistance should be 12-14 ohms...but also just to be safe would test spark
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Old 07-03-2010, 09:40 PM   #3
redhotftw!
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Join Date: Oct 2009
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clean the grounds under the icm, possible bad ICM. the ICM is the unit the coil packs bolt to. your compression is below the 180 service limit and the car needs a rebuild.
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