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Discussion Starter · #1 ·
A while back I started getting a misfire in my engine. I had terrible acceleration and a very jumpy idling. I wasn't getting any error codes so I looked it up on here. A lot of people said clean the throttle body and use injection cleaner. The throttle body didn't help at all so I used injection cleaner and it helped a little. I figured it was a fuel issue so I replaced the fuel filter and that helped a lot but I was still receiving some form of misfire. I checked the ignition coils 5 we're old one was only 2 years old. The gaskets on the old ones were cracked and I found watery oil pooled in the wells. I cleaned it all up replaced the gasket and two sparkplugs that were in the most pooled Wells. (Note: I checked the cylinders and they were dry so the oil/water I'm assuming came from the cracked coil gaskets. It ran much better after that but I'm still getting a misfire with no error codes. Also if it helps my mpg is 12.1 when it is usually about 15. I've also checked my vacuum lines and they seem to be in rly good shape. Is there a reason I wouldn't be getting a code for a failed spark plug or coil?
 

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Welcome to the forum.

OBDII codes for cylinder misfires only set when the misfires exceed a certain number of misfires in a given time period. That is why P0300 (non specific cylinder misfire) can often be troublesome to track down. Rather than the coils you replaced being bad, they were likely in a degraded condition such that there were only misfiring intermittently.

Best way to diagnose these engines is to start with reading the OBDII system with a code reader/scanner that can read historical and pending codes in addition to codes that are set.

You do not mention how you read the OBDII codes. If you are in need of an ODDII code reader/scanner that is extremely capable and can do most anything, and you have an android device, I recommend using the Torque Pro app ($5.00) plus the following OBDII Bluetooth Dongle:


Several of us on this forum use this set up on an almost daily basis and it is amazing at all it will do.

Good Luck!
 

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Discussion Starter · #3 ·
Welcome to the forum.

OBDII codes for cylinder misfires only set when the misfires exceed a certain number of misfires in a given time period. That is why P0300 (non specific cylinder misfire) can often be troublesome to track down. Rather than the coils you replaced being bad, they were likely in a degraded condition such that there were only misfiring intermittently.

Best way to diagnose these engines is to start with reading the OBDII system with a code reader/scanner that can read historical and pending codes in addition to codes that are set.

You do not mention how you read the OBDII codes. If you are in need of an ODDII code reader/scanner that is extremely capable and can do most anything, and you have an android device, I recommend using the Torque Pro app ($5.00) plus the following OBDII Bluetooth Dongle:


Several of us on this forum use this set up on an almost daily basis and it is amazing at all it will do.

Good Luck!
Thank you for your reply! Yes I have my own scanner and there are no stored codes or pending codes at the moment. Is there a way to test the coils to see if they are bad? I'm fine with replacing the rest of the plugs as they are cheap, but a set of coils would be around $300.
 

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OK on having an OBDII code reader.

There is no official way to test the ignition coils. A few people have measured the resistance between the various pins and between the case and the pins, but what it all means is unknown.

Ignition coils normally are not considered wear items like spark plugs, and the best way to proceed is the flip of a coin - one set of people says to replace all the coils when one goes bad, and another set of people says to replace only the defective coil.

One thing is certainly true, if and when you do replace a coil or coils, be sure and use a quality coil and not some white box, price too good to be true chinesium coil as those will likely not work properly for very long. Choose a coil from ACDelco, Delphi, Standard Motor Products (non T series), NAPA Echlin, or BWD (non P series). Those are darn good coils and will last a long time. Also, if you purchase them on rockauto.com, you can save a lot of $$$. For example a coil from SMP costs just under $41, a Delphi Coil costs just under $43, and (GULP), a Genuine GM coils costs just under $102.

Quality parts don't have to break the bank, but they can save you money in the long run in that they will not have to be replaced as often.
 
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