cylinder #4 misfire

[tjbev21]

if your cars not running rough through out the whole rpm band its probably not a coil pack... the 2 coil packs that went out on me the car ran like shit at every RPM... when just my injector was bad it was just rough at idle

[blaketiernay]

Take the plug out use a bore scope see if there is any scoring in that cylinder if there is low compression it might be a bad valve or piston rings are burnt same thing happend to me now i gotta rip the engine out and send it to a machine shope or replace the hole lower block

[chuckzul]

Well, the shop I initially took it to said they did a compression test on #4 cylinder and found it to be low (~45 psi), but they admitted they don't get many Subarus and don't understand them very well. I'm going to replace the injector to see if that works, if not, I have a coil pack. If that doesn't work, I may have to take it to the shop. What's the cost involved in having a burnt exhaust valve replaced? If it's too high, I may end up just selling the car altogether.

[Underdog]

Injector/coilpack isn't going to fix the compression. Compression checks are the same regardless of engine layout: pull fuel pump fuse, plugs out, throttle open, compression tester hooked up to cylinder you want, crank it over.

 

The shop should have put a little 30wt oil in the cylinder and redone the compression check. If it improved slightly it's your rings, otherwise it's a valve. If both cylinders on the same bank are low it could be a head gasket.

 

Good luck!

[chuckzul]

They did not elaborate on their testing methods, only that they had done a compression test and checked the spark plugs (which they said looked good to them). I would have thought that worn rings would be evident by blackened plugs. The oil and the anti freeze look fine, no oily or foamy residue. Honestly, it does not look to me that they even took the coil pack off as it looked just as dusty as it did before. One thing I did forget to mention is that I thought I smelled a more fuel enriched exhaust than before and I did get a flashing cel at one point. From what I can find, a flashing cel usually indicates impending damage (usually to the catalytic because the 02 sensor has discovered too much fuel in the exhaust) and to stop immediately. This is why I will replace the injector first and see what happens. Again, if the head gasket or valve needs replacing, I might as well just sell the car.

[VTownGT]

Chuckzul,

 

What is the current status of your situation? I have a problem that seems similar to yours. I have tried swapping the coils, injectors, plugs, etc, etc, but I am still getting the misfire. Now I have to get a compression test, I suppose.

 

On my most recent time standing over the idling engine, I realized that chirp that I have had for a while now (that I thought was a slightly loose PS belt) actually seems to be coming from the motor under the TMIC. Have you had that? any idea what it is?

 

Thanks

[chuckzul]

Chuckzul,

 

What is the current status of your situation? I have a problem that seems similar to yours. I have tried swapping the coils, injectors, plugs, etc, etc, but I am still getting the misfire. Now I have to get a compression test, I suppose.

 

On my most recent time standing over the idling engine, I realized that chirp that I have had for a while now (that I thought was a slightly loose PS belt) actually seems to be coming from the motor under the TMIC. Have you had that? any idea what it is?

 

Thanks

 

Well, I've replaced the drivers side OCV, #4 injector, #4 ignition coil, and all new spark plugs. I'm still getting a P0304 error. I've been a mechanic for almost 30 years, but I'm stumped on this one. There are still several things to look at. Bad cam/crank sensor, valves out of adjustment, the #4 exhaust cam could have slipped a tooth, some other sensor I can't think of, or, worst of all, a burnt valve. The symptoms I'm still having are a choppy idle (almost to the point of dying), but it smooths out the higher the rpm's. A repeating P0304 code, and a popping noise from the exhaust after revving the engine. There is no oily residue in the anti freeze or "milky" colored oil, so, I can assume its not a head gasket. The spark plugs were fine, except #4 which was black and sooty (the #4 exhaust port was also black and sooty) and smelled like gas, so, I can assume for now its not pistons or rings, For obvious reasons, I rarely take my car to the stealership, but, I'm going to throw this one over the fence to them because they have more sophisticated testing equipment than I do. I may try and pull some data logs on it today to see if I can see a smoking gun. I know there is a blue vacuum "T" under the TMIC that people have reported coming loose, but, I don't think mine has. My gut feeling is that it is probably either a burnt #4 valve, or valve adjusment/timing issue on that exhaust port. I'm hoping this is a simple problem to fix (i.e. some odd vacuum leak or timing problem) or I'll be forced to trade the car in on something else. I'll know next Tuesday when I take it in.

[VTownGT]

I changed the oil again today to see the condition of it. The oil is 5w-30 Syntech with about 3000 on it. No milky color, but it did seem to have less viscosity than the used oil that I have seen during oil changes prior to all the misfiring.

 

While I had the car up on ramps, I was under the car with it idling before and after the oil change. That squealing noise that I first thought was a belt, then I though was coming from the top of the motor, is loudest from under the car. I have no idea what it is, but I can not imagine that it is not related to the problem.

 

It sounds like a screech that you would hear from a bad bearing that has a lot of load on it. I have no idea what that could be... any ideas would be super helpful.

 

Also, when I check the code today before I started working on the car, the car also had a P0301. Previously, I saw a P0304 all the time, and a P0303 most of the time to go with it.

 

Lastly, the CEL is on solid all the time. But when I am driving, and sitting at a light the CEL starts to blink, especially if I have the clutch in. It stops blinking if I go to neutral with the clutch out, or it stops when I start moving again. Any ideas about that would also help me a great deal...

 

About a week or so ago, I pulled the TMIC off to get to the hoses under there, including the Blue T connector. All of the hoses were on there just fine, but I added some zip ties while I was at it.

 

FYI: I found it much easier to get the TMIC off than to get it back on. There is a good walk-through on here somewhere, but I can not seem to find the link again.

 

On Monday, I think that I might give Wayne, NJ Subaru a call to see if I can get an appointment there soon. I got a recommendation about the place from Bruce at Bruce's Speed Shop that they are a family joint and know what they are talking about...

[derffred]

While I had the car up on ramps, I was under the car with it idling before and after the oil change. That squealing noise that I first thought was a belt, then I though was coming from the top of the motor, is loudest from under the car. I have no idea what it is, but I can not imagine that it is not related to the problem.

 

It sounds like a screech that you would hear from a bad bearing that has a lot of load on it. I have no idea what that could be... any ideas would be super helpful.

 

...

 

This may be a different concern from you, but I had a noise from underneath my car.. sounded exactly like a belt squeak at idle, but it ended up being my downpipe bracket (where it bolts to the Transmission bracket), it was cracked behind the center of the bolt, causing a chirp noise. Fixed it by just installing a bigger washer. Idk if it'll help, but check it out just in case.

[dudeondacouch]

The belt-squeal sound is probably your throwout bearing going.

 

Does it stop when you push in the clutch pedal?

[VTownGT]

dudeondacouch, thanks!

 

The good news is that it does stop when I push in the clutch, which means that I probably need a new clutch soon, and that is not a huge surprise as it has more than 114 K miles on it...

 

The bad news is that I do not think that is what is causing my misfire(s).

 

Thanks again!

[Listerine]

VTownGT,

 

Get that throwout bearing changed sooner than later. I had the same issue with the squealing back in February and last month the TOB seized and took my clutch and transmission with it.

 

I've also got a P0304 misfire CEL, but i'm hoping its just the injectors. I've swapped #3 and #4 and the CEL has yet to come back...

[05lgt5spd]

^^^weird I did the same thing. Even swapped changed plugs, and swapped coil packs. Do you still hear/feel the car missing?

[dudeondacouch]

dudeondacouch, thanks!

 

The good news is that it does stop when I push in the clutch, which means that I probably need a new clutch soon, and that is not a huge surprise as it has more than 114 K miles on it...

 

The bad news is that I do not think that is what is causing my misfire(s).

 

Thanks again!

 

If your stock clutch has that many miles, you have done better than most. I would recommend getting a new one rather than just changing out the TOB, as it will be more $ for parts, but you'll only have to pay for (or DIY) the labor once. It's a PITA.

[chuckzul]

Well, cleared the CEL and ran some RomRaider logging. A/F is fine but #4 cylinder roughness was registering a constant 92 while the other cylinders were 0 (though #3 registered 1 misfire). I'm not really sure what parameters to run for this situation. But, on a whim I decided to remove #4 ignition coil and spark plug. The plug was clean but on closer inspection, I could smell raw fuel on it, so, I am wondering if there is even a spark? Is there something (i.e. cam position sensor) that tells each individual coil when to fire? I'm still not sure or any closer to finding the "smoking gun" on this one.

[Listerine]

^^^weird I did the same thing. Even swapped changed plugs, and swapped coil packs. Do you still hear/feel the car missing?

 

 

Yeah Its still misfiring, but I can only hear it after its been driven. In the mornings I start up the car and as its warming up theres no misfire.

[derffred]

Check for vacuum leaks! My car's intake manifold gasket was leaking causing a miss on 2 and 4. Only happened during or after warmup.

[chuckzul]

Well, got the dreaded phone call from the dealer. They said there is no cpmpression in #4 cylinder. They said it's either a burnt valve or rings. They said they would have to spend 15 hours tearing the engine apart to find out what the exact problem is at a cost of $1400 (roughly). I'm calling BS on them. To spend $1400 just to find out what the problem is, is horse crap in my book. Seems my options are very limited other than trade/sell the car off for what I can get for it.

[derffred]

Well, got the dreaded phone call from the dealer. They said there is no cpmpression in #4 cylinder. They said it's either a burnt valve or rings. They said they would have to spend 15 hours tearing the engine apart to find out what the exact problem is at a cost of $1400 (roughly). I'm calling BS on them. To spend $1400 just to find out what the problem is, is horse crap in my book. Seems my options are very limited other than trade/sell the car off for what I can get for it.

 

They have to take your cylinder head off to see whats goin on. To do that, they have to pull the motor... if you go for the diag, you might as well go for the whole repair..

[nka]

Check for vacuum leaks!

 

How to ?

[chuckzul]

They have to take your cylinder head off to see whats goin on. To do that, they have to pull the motor... if you go for the diag, you might as well go for the whole repair..

 

Well, there are 2 simple things that would determine if it were rings or valves without tearing out the engine. First, the spark plugs were carbon fouled not oil fouled and it didn't smoke or burn oil, so, it's probably not the rings, but, they could have squirted oil or ATF into the cylinder and re-run the compression to see if compression builds up or not. If it does, its rings or cylinder wall gouging. If compression does not build up, you turn the engine until the #4 cylinder exhaust valve is closed, then connect an air source to the cylinder and pressurize it, if air comes out the exhaust, its valves. I mean, these are from Automotive 101. Seems to me all they did was just hook up the computer, run a quick compression test, and call it a day. What bothers me the most is that they want me to make a $1400 decision based on $93, basically an hours worth of work, on shoddy, half assed trouble shooting. Honestly, I would be ok with spending a grand having the car fixed if I knew it needed valve work (multiple thousands on a new engine, not so much), but I need to know up front what I am dealing with before I'm willing to part with that kind of money, and I am just not that williing to spend $1400 on tearing an engine apart to just turn around and sell it because it needs an engine rebuild. I think its shameful on Subaru's part to sell a car that is disposable after only 62K miles.

[chuckzul]

They have to take your cylinder head off to see whats goin on. To do that, they have to pull the motor... if you go for the diag, you might as well go for the whole repair..

 

Well, I got the final post mortem on my ex-Legacy. Turned out to be a ring (cracked/broken) on one cylinder which caused some scoring to the walls and a carbon fouled exhaust valve on another. The estimate to fix this was $5-$6k (basically a rebuilt motor). This doesn't include the clutch or the brakes which would have needed replacing this year. Good thing I dumped that turd while I had the chance. Having read more and more stories about aging Legacys, I'll never buy another one and I won't suggest to anyone else to buy one either. Long live the Dodge Ram 1500 Hemi.

[nka]

damn...

[Listerine]

I just fixed my stutter/misfire issue (CEL P0304) after doing the plugs, then a coil pack, then today an injector, I'm happy to report that it doesn't seem to be stuttering anymore, running much smoother. Time will tell if the check engine light comes on again but I'm pretty sure I got it.

[VTownGT]

So... Its been a while since I updated. I had Misfires on #4 all the time, and sometimes on 1 & 3 and some engine squealing. What I was hoping to just be a stretched timing belt and a noisy throw out bearing was actually (almost) the worst it could be...

 

I had to replace the short block. The crank bearings were wearing which was putting some metal into the mix of problems, and in addition, there was piston damage on #4, causing misfires on that cylinder and the others. I did not even try to find out if the block was repairable, I just went for a new short block because it would give me piece of mind. The only way that it could have been worse would have been if the heads were screwed up, too. Luckily, they weren't because I would have not gotten the car fixed had that been the case.

 

The repair work was done at EFI Logics up in CT, who are like a jar of awesome sauce. (I called them on the recommendation of Mike P from AZP Installs, who is like two jars of awesome sauce. More on this below.)

 

It was worth getting the car fixed 100 miles away because as soon as you walk into EFI, you know that all they think about are Subarus. I originally took the car there thinking that the problems were somewhat minor, and when they looked at the car and realized that it was a bigger deal, Chris from EFI called me, asked me a ton of questions about the history of the car (to see if I had bought it used and had been scammed, etc. I let him know I took delivery new with <10 miles.) Then he and Pete laid out my options, costs, put the whole thing in writing, and did the work faster than they promised, which was refreshingly great service.

 

Regarding Mike at AZP... he deserves your business. When I was trying to figure out what was wrong, he met me late on a Friday night at his shop in NJ to look at the car with one of the other AZP guys. Then, he recommended some inexpensive things to try first before getting the above work done, helped me order parts cheaper than I could get them myself, AND, to top it all off, he would not take money from me when I offered to pay him for his time.

 

(If there is a place on the forums where I people are most likely to see my feedback about these two businesses, please someone let me know.)

 

So, the bottom line... about $6400 for everything. That included the short block, all belts, all gaskets, a new clutch kit, an new and upgraded oil pick up, higher quality head bolts, all fluids including three oil changes, spark plugs, and probably some stuff that I am forgetting to list and the labor.) If I include the costs of things that I tried myself to fix before I went to EFI, my total costs are probably in the low $7000 neighborhood, along with a lot of my own time trying to fix stuff myself and and a lot of favors owed to people who were kind enough to drive me around while I had not car for about a month.