P0304 Trouble code

[kj0426]

Hello... I am new to the site. I just purcheased a 2004 Ion 2 Sedan with 95,000 miles. I purchased the car knowing the it had a cylinder 4 misfire. Prior to ourxhasing it I researched what it could be causing the code. I figured it was a plug, coil, or ICM, etc since it seems pretty common in these cars. I changed all three but no luck. The next thing I did was swap injector 3 and 4 to see if I could get the code to move to another cylinder. No luck there either.

Does anyone have any other suggestions before I wind up taking somewhere that will cost me a fortune? I'll probably do a compression test to rule out anything major.

The car seems to run fine with plenty of power but runs really rough at idle. Any help would be greatly appreciated.

Thanks in advance!
Kevin

[kj0426]

One more question... Is cylinder #4 the one to the far right?

Thanks,
Kevin

[2006 ion2]

looking at the engine from the front of the car, number 4 is all the way to the right.

[kj0426]

Thanks for the response. That's what i thought. Any suggestions before doing the compression test?

Thanks,
Kevin

[2006 ion2]

remove all the plugs before starting the test. otherwise its pretty straightforward

[lilfoot81]

same thing just happened to me with my 07 on cylinder 2. However it was some valve in the header. COuld be your problem and its covered to

[2006 ion2]

careful, what happened to yours sounds like something specific to the 2.4, which is a far different engine compared to the others in ions. do you know exactly what it was that was wrong, lilfoot?

[kj0426]

Well it looks like I have 60lbs of compression in cylinder #4 and about 200 in all the others. It's probably a cracked valve or severe carbon build up causing the low compression. I don't know too much about this stuff so I don't think I want to tackle replacing the head on my own.

Any suggestions on how much this should cost to fix. I could either get my head rebuilt or I can buy a remanufactured one. Any input would be greatly appreciated.

Thanks again for all the help so far,
Kevin

[2006 ion2]

I doubt the head or valve is actually cracked, knowing how strong these heads are. but the head is relatively easy to quickly remove for inspection/cleaning. if you don't feel comfortable doing this yourself, it should only take a professional about an hour to do this.

[kj0426]

Thanks for the response. I've changed heads before on V8's and V6's but never done one on a DOHC. I heard the timing chain and other stuff can be be a bit tricky. I was quoted $500 for the labor to remove and reinstall. I thought it seemd a bit high but I could be wrong Anyone done a head swap? How was it?

Thanks,
Kevin

[2006 ion2]

I keep forgetting about how the timing chain is routed, it might take more than an hour, but with the right tools and procedures, I don't see it being $500 in labor just to take off and put on a head. you might want to find someone with a bore scope, or do a little more diagnosing with the head on the engine.

perhaps try this: find a way to adapt a hose from a compressor to the spark plug hole so you get relatively little leaking from the fitting(s). take off the coil packs, spark plugs, and intake tubing (not the manifold), and try to find bottom dead center on cylinder 4 or close to it (both valves will need to be closed). you should be able to move the engine with the idler pulley, or you can pulse the starter if need be. then hook up the hose to the number 4 spark plug hole and pressurize it to 40PSI (should be high enough for the purposes of this test, but low enough to not cause any issues), you now need to listen for hissing from 1. the exhaust tip, 2. the throttle body, and 3. the PCV hose. if you hear a LOT of hissing from the intake or exhaust, make sure you are in a spot where both valves are closed, if one side always hisses a lot, you have the bad side. if you hear hissing from the PCV hose, you have bad rings or you need to run the engine for a minute or so to realign the gaps right to not be leaking.

this compression leak test should tell you where to look more specifically, and you should be able to do this yourself. this along with a bore scope to further pinpoint the problem should minimize down time for the car, and hopefully how much the repair costs, as well. good luck, and please keep us posted.

[kj0426]

Thanks again for all the help. We did do a leak down test and the pressure didn't change so it mus be a bad valve.

I'll probably have to get a valve job. Do you know if HAVE to purchase new head bolts or can I just re-use the exisiting bolts? I don't want to sound cheap but I am trying to save as much $ as possible.

Also, can I use a felpro paper gasket or should I splurge for a copper one?

Thanks,
Kevin

[2006 ion2]

I would use a copper gasket, and would not reuse head bolts.

if you have low compression, but you don't lose pressure in a leak test, that is rather odd... maybe you have a bad rocker, not the valve itself. the only way to really tell is to pull the head.

[kj0426]

After pulling the head we noticed that one of the exhaust valves on cylinder 4was cracked. Kinda looks like pacman.

The head is at the machine shop getting a full valve job. She should be purring like a kitten in no time.

Thanks again for all the help.

Kevin

[Maritime Storm]

Actually what you described sounds like a burnt valve. Post a picture if you can. The head bolts are torque-to-yield, do not re-use them.