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Chris Bedard 09-06-2016 01:30 PM

Low Compression #4, P0304 Code
Yet another low compression thread, sorry.
Car is a 2002 SC2 DOHC 1.9, manual trans, has just under 200K miles.
I came at this problem kinda backwards. It was throwing the P0304 code and my inspection sticker was coming up so I needed to get it fixed to pass inspection.
Replaced plugs and wires, IAC valve, EGR. Code persists. Replaced coil, no change. Replaced ICM, no change. Swapped fuel injectors for #4 and cylinder next to it, #3? No change. No oil in spark plug tubes. OK, tiny amount.
Finnally checked compression, engine cold. All cylinders peaked in pressure after about 5 seconds or less of cranking.
#1, 160psi
#2, 150psi
#3, 150psi
#4, 60psi.

OK, clearly that's my P0304 problem. I have not done a leak down test to determine if it's valves or rings. I suspect valve.(s) It does use oil but I don't think I'm burning it. I think it's leaking. There is no noticeable blue smoke.
So... at 200K miles I am REALLY not interested in putting in an engine, or replacing a head. But if I have to have a valve job done then I will.
Is there a quick and dirty way to make the P0304 code go away long enough to get the inspection sticker? If I unplug the #4 fuel injector will it stop throwing that code?
Thanks for any info!


fetchitfido 09-06-2016 01:49 PM

Re: Low Compression #4, P0304 Code
With numbers that low that engine is just simply done.

I doubt it'll fix the misfire code but unless the injector plug argues more than normal it takes 10 seconds to pop it off, then 35 to remove the negative battery cable to clear the code. Then drive it around for a while, see if the CEL comes back on.

Chris Bedard 09-07-2016 12:15 PM

Re: Low Compression #4, P0304 Code
I pulled the FI plug and while it did not immediately throw a code, it did run much worse. lol So I guess cylinder #4 is still firing to some extent. It runs bad enough that I'd rather not have to drive it around like that for 150 miles before I can go in to get the inspection sticker.
It does only throw the P0304 code intermittently so I"m going to try to gamble on getting to 150 miles without getting a code and then run in to get the sticker.
Hopefully that will happen. About 40 miles so far.

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