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Discussion Starter #1
I have a 2002 accent with 150k on it, it has been a great car but recently, it started to misfire at idle, quite badly. but as soon as I rev it up over 1000 rpm the light stops flashing and it runs like a dream until I pull up to the next red light and let it idle again. i scanned a p 300, p 301, p 303, and a p 304. I immediately changed the plugs and wires figuring that would be the problem. still misfiring. then the coil because I have heard they can be an issue. still misfiring. dumped a bunch of sea foam in the gas to see if the injectors were dirty, still misfiring. (I usually put injector cleaner in every 5000k with oil change anyways). changed pcv valve, fuel filter, and checked and cleaned every electrical connection with contact cleaner on the car. still misfiring at idle.

Anyone on here every experienced this or could offer me some assistance?
Could it be the map sensor or the pcsv? even if they dont come up on my code reader?

Any help would be appreciated!

thanks!

Al
 

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Discussion Starter #4
Well... I did the compression check like you suggested, and I had 120 psi on #1 and 150 - 165 psi on 2,3 and 4... so it looks like cylinder 1 could be the culprit. If I had a burnt valve on #1 could this cause the others to miss fire? I re-read the codes and all four cylinders have misfired. I'm lost and don't know what to do next. the only 5 codes I've had are p300, p301, p302, p303, and p 304, and it still runs like a dream once the rpms are up past idle.

any more insight?
 

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If the lost compression is due to a valve stuck open from deposits, you might get lucky by revving the engine and holding it just under red-line for a full minute or two. Only do this after the engine oil is at normal operation temperature. So drive the car for at least a half an hour before you do this. You should also avoid cheap brand gasoline. Switch to Chevron. They are the only major brand that includes detergent (techron) in all grade of gas. Namely 87 octane. Which is what most all of us use in these cars anyway.

If the lost compression is due to a problem with the piston rings, you should consider a product call AutoRX. Sludge build up on the rings can cause compression problems over time. This stuff will clean it out.

If neither of these fix it. Your next best step would be to use a Borescope to look inside the cylinders and check the valve seats. If there is a problem, you're looking at a head job or a replacement. Good luck
 
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