-Misfire...Please help-

[shadow29485]

Hey guys. I'm new to your forum, and have a problem that I'm hoping you can help me with, since I'm new to these GM engines. I'm on many honda/acura forums but this one is about my wifes car.

She has a 2007 Saturn ion 2.2 base model, and I'm pulling codes p303 (cyl. 33 misfire), and p300 (rand. misfire). I've checked spark on all four coils, and they all seem to be firing just fine. I pulled the plug wire on cyl. #3 while the car is running, and it does NOT effect idol at all, which tells me obviously it's not firing properly.

I've replaced the injector, and all plugs are new and gaped to specs. I reset the ecu, and cleared the codes, but it still keeps coming back.

My question is, is this a common problem with these types of engines? And what to check next? ICM? But if I'm getting spark on all plug packs, why is it missing? Could the icm just not be producing enough spark for that cyl.?

Please help, this shit is driving me crazy. She's only getting approx. 15 mi. to the gallon.

Thanks a bunch,
-Shadow29485-

[shadow29485]

Wow! No one has a clue, huh?

[youngrwaggs]

Here is a pretty detailed check list to take a look at. I used this same list for looking into a spark issue on my SL2.

You should have better luck with it.

Troubleshooting Spark Plug Check List

[recaro86]

The ignition modules fail often on the 2.2. It may be acting up under load more than cruising. Check your fuel pressure and confirm that is also in spec. Lastly, a MAF cleaning and map censor cleaning, along with throttle body wipe down never hurts either

[david.dichristopher]

I had the same problem with my 2004 Redline, one cylinder was miss firing randomly. Went through hell and back too find out the problem. But it turned out too be my camshaft positioning sensor. I changed it but still kept getting codes. Turns out it had too be installed professionally because it has too be timed with the certain cylinder that was misfiring. After it was fixed more hp and alot more mpg!(: hope this helped

[david.dichristopher]

The whole deal wasn't that expensive, but trust me I went through the same problems you did. Changed everything from spark plugs and was even thinking fuel pump. Get it checked out, but get it done right. Just simply replacing if wont do, it was too
Be timed with the miss fire

[shadow29485]

Thanks sooo much for the responses guys! I'm gonna check into those.

I just tested compression, and I've got almost 180psi. give or take, thru all (4). So thank GOD it's not internal, such as burnt valves, or seals.

I talked to my local saturn dealer, and they said that they could do a more in depth scan for like 90 bux. that may narrow down where the problem is stemming from.

Would you guys suggest that? I have a obd2 scanner, but I'm assuming the dealership may have some serious software that may give us a more detailed approach at what the hells going on. These cars have a pcm correct? Not one ecu that runs the entire vehicle right?

Thanks again,
-Neill-

[shadow29485]

I forgot to mention that it only does it at idol. And every now and than, you can turn the key, just a tad, and it struggles to start, even if you let go of the key....it keeps trying to fire until it turns over.

[recaro86]

It may be worth it to have them take a look if they can give you an idea for 90 not all that bad

[golden chicken]

A couple of S-series cars I've worked on had bad intake manifold gaskets that caused misfiring. That's the only thing I can think of that would cause your problem after everything you've already looked at--especially if the problem seems to straighten itself out off-idle.