Diagnosis Help Misfire, Now car drives like n/a

I have been getting misfire codes for months and I presumed it was because the previous owner had some plugs put in that may not be correct (didn't do it at a subaru dealer). So I have some OEM plugs ready to go but haven't had the time to install them. I have just been resetting the codes and all has been well. The engine has always shaked a little at idle too but idles very steady.

But today it seemed like I was driving an n/a car. I was making boost though. And it isn't throwing codes. And there are no strange sounds. It would also rev up but it was just gutless.

This is on an '02 WRX with 144k miles that is stock and always has been besides a prodrive catback. I haven't had any oil consumption or smoke and I don't beat on the car. It's my A to B.

Any thoughts? I want to do a compression and leakdown test when I do the plugs. I also intend on replacing the PCV. Could it be clogged cats?

 

definatly get those plugs out

 

Gotta start with the basics. Spark plugs, fuel filter, and air filter. Don't forget to clean the MAF (air flow meter) with some electrical contact cleaner or something similar.

Crappy spark plugs can also burn out ignition coils. They're not too cheap.

Good luck.

 

this sounds exactly like what happend to a wrx at my work, it started to misfire(spark related), eventually plugged the pre turbo cat, the cat started to break up, and the cat went through the turbo..wallah, N/A 2.0... DONT DRIVE IT ANYMORE TILL YOU KNOW WHAT IS UP

 

Hrm... your diagnosis freaks me out

I always use 92/93 octane and the car never feels like it is missing. It just throws the code occasionally at totally random times and I never hear the 'marbles in hands' detonation. Unless it is inaudible minor detonation. Are there many different causes for misfire CELs?

I wouldn't doubt that the cat is plugged but I doubt it has gone through the turbo as it makes no abnormal sound and makes full boost, it just seems choked.

Looks like i will take a break from driving it until I get the plugs in and the compression check done.

 

Well SOB! I just got back from my vacation in Jackson Hole... (unreal, 12" of snow one day!, friggen rocked!) But anyways, I had a chance to pull the plugs and do a compression check.

First, i had suspected the original owner to have replaced the plugs with crap plugs. I was wrong. They had the proper NGK's and gap.

I was more concerned about compression comparisons than actual compression numbers so I never warmed up the car before I did my compression check and I am assuming that is why the numbers are lower than the usual 150. I checked Cylinder 3 several times too to verify.

Cylinder 1: 130
Cylinder 2: 130
Cylinder 3: 90
Cylinder 4: 130

Cylinder 3 was the cylinder I was getting a misfire code from.

So...I am a little bummed. I am wondering if this cylinder had lower compression since I bought it. There was no obvious symptoms of this when I bought it. After 400 miles it did throw one misfire code but I reset it and it didn't come back for 3-4 months.

The car has always been stock I presume. Still has the original up pipe etc. I never drove it hard. I suppose the previous owner could have. The car has 142k miles on it.

I am guessing that the misfires caused extra fuel in the cat and it is now plugged and thus the n/a like acceleration symptoms.

So now my options. I am guessing either a cracked head, bad rings, or a burnt valve. I have heard that if you squirt some oil in the cylinder and then do a compression check you can determine if its rings or not because the oil will seal up the rings. Anyone ever try this?

I am guessing the motor needs to come out regardless... Would it be a sin to throw in a catless up pipe (so I don't wipe out my turbo) and keep driving it?

My replacement options are:
1. fix old engine $500-1000
2. rebuild old engine $1000+
3. buy used long block, replace and cross fingers $1000+
4. Do an STI engine swap $4000+
5. ?

 

I will put money on it that it is a burnt valve, have seen this on several WRX's. Every car that had this problem, was caused from running Holiday fuel, all the owners said that was all they ever ran in their cars.

 

Interesting...This would explain why there has been no oil consumption. I have used holiday gas, but that is not all I have used. Space seems tight...does the engine still have to come out? (I think its time I get the factory service manual.)

I pulled the OEM up pipe tonight. It isn't as hard as everyone is always saying it is. I am thinking about putting in an aftermarket downpipe with the up pipe. Is there anyway to verify if the up pipe cat is clogged?

 

Yes you would have to pull the engine out to fix it if it is a valve, and I really doubt the U.P. is clogged, if anything they break down in to pieces.