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I have had a persistent CEL for a while now with the following codes:
P300: random cylinder misfire
P303: cylinder 3 misfire
'02 GTS. Symptoms: hesitation in the morning or when the engine is cold; engine sputters lightly pretty much all the time (can be heard from the air intake and exhaust).
I really need to take care of this if I want to pass another state inspection (that's been expired for over a year and a half now.. whoops). The only relevant mod that I can think of is the Injen SRI. I did the BB mod since I've had the problem, but the codes have stayed the same.
[Engine Bay]
Troubleshooting I have done so far:
- cleaned the MAF sensor multiple times
- replaced the spark plugs (iridium); moved the spark plugs and the coils around, code P303 stays on cylinder 3.
[Spark Plugs]
- ran fuel injector cleaner through the gas tank
- sprayed intake cleaner around the manifold area to see if any leaks would show, but did not notice any difference
- seafoamed the car
- ran a cylinder compression test today, got 151, 154, 147, and 155 psi for cylinders 1-4 respectively. This is lower than normal, no?
My mechanic said they took out the injectors and cleaned them, but I will check them again myself. Besides that, I'm not sure what else I can besides take the manifold off and take a look (never done this before, so I wouldn't be sure what to look for). My shop said it'll be around $2K for them to take the head off the motor. Any suggestions or ideas of what I can do myself?
P300: random cylinder misfire
P303: cylinder 3 misfire
'02 GTS. Symptoms: hesitation in the morning or when the engine is cold; engine sputters lightly pretty much all the time (can be heard from the air intake and exhaust).
I really need to take care of this if I want to pass another state inspection (that's been expired for over a year and a half now.. whoops). The only relevant mod that I can think of is the Injen SRI. I did the BB mod since I've had the problem, but the codes have stayed the same.
[Engine Bay]

Troubleshooting I have done so far:
- cleaned the MAF sensor multiple times
- replaced the spark plugs (iridium); moved the spark plugs and the coils around, code P303 stays on cylinder 3.
[Spark Plugs]

- ran fuel injector cleaner through the gas tank
- sprayed intake cleaner around the manifold area to see if any leaks would show, but did not notice any difference
- seafoamed the car
- ran a cylinder compression test today, got 151, 154, 147, and 155 psi for cylinders 1-4 respectively. This is lower than normal, no?
My mechanic said they took out the injectors and cleaned them, but I will check them again myself. Besides that, I'm not sure what else I can besides take the manifold off and take a look (never done this before, so I wouldn't be sure what to look for). My shop said it'll be around $2K for them to take the head off the motor. Any suggestions or ideas of what I can do myself?