Hi all,

My engine has been running like crap for a few months. I did all of the maintenance you can imagine. If you want to ask me if I've changed specific parts than please do so, but the answer will most likely be yes.


My roommate has come to the conclusion that I have low compression specifically in cylinder number one, causing the following symptoms:

Power loss
Misfire at startup
Extended crank
Shuddering when first starting off cold
Poor mpg
P0301 and p0300

I ran into a forum where someone claimed a stretched or worn timing chain can cause loss of power and low compression.


I have reason to believe my timing chain is the culprit but honestly I have put too much money into diagnosing this motor and don't want to drop any more without verification.


The reason I think it is the timing chain is because of the fact that my ECU seems to correct itself after it goes through its temper tantrum every morning. I take off out of the driveway, as soon as the rpms go above ~2k the engine begins to misfire and has no power. Moments later everything is normal again but the butt dyno and my wallet (gas costs) say something isn't right.


Compression in cylinder 1 was below 50 at first crank. It eventually made its way to 143 psi. The other cylinders did not seem to follow this trend, they did not start low like #1 but they were still a bit low for comfort. We tested cylinder #1 first. Could the ecu have noticed the timing was off and corrected it before we moved on from cylinder 1?

Please chime in guys, I've posted up about this before but nobody got back to me. I really do need help yes I've searched 1000 times.

 

That may actually be normal. It takes a few strokes to really get the final reading. I've always noticed a low number on the first crank on any car i've done this on.

Basically you just crank it over until the needle stops rising and that's your compression for that cylinder. You then compare to all of the other cylinders and they should be within 10% of each other.

If 1 cylinder is low compared to other, add some oil to the cylinder via the spark plug hole and retest. If the numbers come up, then its possible they are bad rings. If not., then a valve problem.

If 2 cylinders are low next to each other, possible blown head gasket.


P0301 does point to a misfire in cylinder #1.

Couple things i'd look for. How does the spark plug look? Normal like the other 5, or is it sooty or oily?

Next i'd probably swap two coils around and reset the engine codes and see if the P0301 moves to another cylinder.

If no change, i'd probably do the same with a fuel injector and see if the code changes to another cylinder.

 

Thanks for replying. I swapped my injectors with 6 new ones a while back as part of my diagnosis. The plugs looked uniform and there is no oil at all leaking from the plug wells. I also swapped ignition coils around with no luck a while back. I have an aftermarket fuel pump-a 255lph walbro, are they prone to slow failure? Are there any parts of the fuel system that need special treatment? Already tried the dampeners because of a noise issue.

We did see a rise in compression when adding oil into the cylinder but I'm not sure if it was significant. I believe cylinder 1 was at143 and the rest were in the 155 range but none were above 160. No two were low next to each other and I haven't seen any coolant level fluctuation. I think I got about everything..... I'm on my phone so you know how it is!

 

Anybody else at 155k without doing their timing chain?

 

I haven't touched my chain at 150K. No intention on doing it either.

Sounds like you've checked out the mechanical issues I was thinking of. Cyl 1 is low, but still within 10% of the other cylinders, so I wouldn't suspect that just yet.

You state the car runs like crap when cold, but fine when it warms up. Makes me think you have an issue with open look running vs closed loop.

Can you hook an OBD2 scanner up to it and monotor live data? Basically monitor the coolant temp as it warms up and when the car switched from OPEN to CLOSED loop. I forget which param lists this but it's stated as OPEN or CLOSED.

I wonder if there is a correlation of the car running better when it switches to closed loop.

Does this car have any sort of tune on it? Or stock ECU and tune?

Might want to google search "Car runs poorly in open loop" and see if anything pops up that sounds familiar.

 

I'll have to get my hands on a scanner to see what the o2's are putting out. Where would be a good place to look for one capable of this, considering I am a broke engineering student...? I would rather not let my roomate borrow my car for the day and bring it to school (NEITautomotive), he would probably try to race his buddies haha.

Both o2's in the rear are new, but it is possible that I have a wire switched on my passenger side one because my harness was taken off during an encounter with some pavement... I am not seeing a CEL from it, so I am assuming I wired it up correctly.

Is a failing fuel component a possibility?

As for a tune, I have an uprev dyno tune through RDZ motorsports in CT and haven't changed anything since being tuned. I did notice a hard time starting after getting the tune so I went back to have it looked at. Unfortunately the car was warm at the time so he could not see what was going on but he did manage to make that go away, at least temporarily... Originally he tuned the car up in 3 quick pulls, he seemed like he knew what he was doing... I did not feel any loss of power at that time like I do now along with the extended crank time.

I don't hear/feel the motor really opening its lungs like I used to at WOT.

There are a lot of possibilities floating through my head... I even get a hint of what I would interpret as tranny slip every now and then around corners... I think both my motor and transmission are on their way out.

What a mess...