Misfire.... Please help.

[Gregory]

Hey guys. Sorry if this is long, but I felt the need to be very descriptive. I've been dealing with the same problem since I've owned the car (about two years). Under full throttle, at about 5.5-6.5k, the engine will lose power and it seems like I'm pushing it way too hard. It's not fuel cut. It still is accelerating, but seems to lose power greatly in the rpm range that I'd thought it would be strongest. If I get off of it or shift right as it's starting to do it, it pulls through the next gear fine up to about that range. If I continue to go through that hesitation range (up to about 6.5k, not even to redline), it throws the CEL and will diagnose as misfire in cylinder four. I bought whatever pep boys recommended for new plugs and wires, but it still did it. I switched those Bosch plugs out for the NGK BPR6ES, and it still does it. Checked gaps and still were where I left them at .28. I dropped gaps down to where I am now at .24, and it still does this. Do you think the wires I have are causing this? They still are very new. I forget what brand they are off the top of my head, but it's the stock replacement they recommend. I've searched this topic greatly many times, and refrained from starting a thread on it, but every time it seems that someone has this problem, the thread just drops off and ends like no one knows what to say. I'm running 14psi with an EVO III 16g. Thanks for any help.

 

[Talonracn50]

I think that your compression is abnormally low. Was the engine warmed up and the throttle open when you performed the test? Most 2G's that I have seen are up around 180.

 

[Gregory]

I used to have a misfiring problem along with a sputter. I found out it was my Barometric Pressure sensor, Might want to check that out too.

I have no idea how to check that, but I'll find out, and do that. Can you describe what your car sounded like?

 

[Gregory]

also remove and check the TPS sensor. if you dont want to take the throttle body off.. you'll need a footlong extension with i believe a 8mm socket on a rachet wrench. very easy to check, i forgot the numbers exactly, but they're in the hayens book.

I'll check that too, thanks.

 

[Gregory]

I think that your compression is abnormally low. Was the engine warmed up and the throttle open when you performed the test? Most 2G's that I have seen are up around 180.

I've heard different number from 136 to 160 for service marks for compression. I actually did not have the throttle open during the test though. Is that how it should be done? Will that affect the test a lot? I don't have the tool for it myself, and I'd have to bother my friend at his shop to get another test done. If you say it's worth it though, I will do it absolutely. Thanks.

 

[Talonracn50]

The throttle should be at wide open during the test. You should unplug the coil pack and injectors during the test.

If it pumped those numbers with the throttle closed, it is probably fine. A tester only costs about 20 bucks from the auto parts store.

 

[Gregory]

Yea, I'll probably go invest in one next chance I get. Thanks!