So I kinda need some help guys, I did the compression test on all the cylinders yesterday. On Cyl 1 (first test) jumped on the dial to above 120 on first stroke then 150 on second stroke. All of the cylinders made it to 150psi. Then I did a wet test and cyl 2 and 3 went up in compression by at most 10 psi. Is this normal? :confused:

I was reading that compression should be between 155 and 180

I think the leak down test will give you a better indication. Something I wanted to do, but don't have the tool for it. What did the wet test show on cylinders 1 and 4? Sounds like its something head related?

^ thanks man, thats what im hoping!

Anyone know if 150psi compression across all cylinders are good or what???

How many times did you let it turn over? Iirc I think you are supposed to let it hit a compression stroke 4 or 5 times.

Yeah, i let it complete 7 compression strokes per cylinder

Don't the 2.4L Ecotecs have higher compression at around 10.5:1? I would think your numbers should be higher across the board. For the 2.2L with 10:1 compression I think the healthy range is like from 180-210 psi.

Thats what i was under the assumption of. I looked at some numbers and people were saying that the correct compression should be anywhere between 155-180 psi. Hence, 150 psi has me worried at the moment.

I am hoping someone that has knowledge of this will be able to chime in.

As long as there isn't much variation between cylinders you are probably OK just signs of a worn engine. Not ideal but I don't think the compression is causing your misfires unless you have significant variation between cylinders.

When I did my compression test, dry it was around 162-165 all four cylinders. When I did the wet test, it jumped to close to 200. I'm just chalking it up to worn rings. I thought I heard somewhere that you don't want to go below 150, but if what JD said is correct...From what I remember, if the wet test shows only a slight increase in PSI, then the problem might be head related and not the pistons (like valves not seating correctly)
You might get more answers posting these questions to either the "general cobalt' or "problems" page where more people are likely to answer.
I did a lot of learning by watching "Eric the Car Guy" on You Tube, Lol. Thank God for the internet, although you can't always find all the answers.
Good luck man!

Ok so that is good news, and i definitely read the same thing. What really ticks me off then is this isnt the original engine, i replaced it for supposedly one with lower mileage. It had about 40k miles on it. So in other words, the A holes who sold it to me ripped me right the frick off! :cussing:

moving on from that then, im having a hell of a time determining what is doing this then.

Here is what i have noticed, after doing the compression check, I went ahead and loosened up all the head bolts in hopes that maybe i just didnt seat the head correctly. Here is what ive found:

1) there is less misfires overall, but its running slightly worse.

2) when it is idling at first start-up of the day, it idles pretty good. AS SOON as i shift to reverse and start backing up, the idle drops all the way to 500 or lower and the misfires happen like crazy.

3) its more sensitive now (after retorquing everything) when accelerating as it starts to buck and cut out.

So im just really lost at this man.

Like you are saying, if it was rings the wet test should have made a significant improvement in compression.

I wonder if it is possible if Cobalt_Noob's timing is off a tooth on one of the cams. I have never done that but I know they can be off a tooth and still run.

Hmm......... Is there anyway to know for sure or just to redo it completely???

I don't know of any. But before you do that maybe someone else will chime in that has had this happen and knows more what the symptoms are.

Even so, i will be doing a leakdown test in the near future to help possibly further shed some light (air?) on the situation. But ive got a hierarchy of possibilities in my head. Whatever it is, its almost like a phantom misfire (which it isnt incase anyone throws that out there!).

Hopefully someone does chime in man.

To check timing, you could start out by pulling the valve covers off and hand crank the engine until both colored links line up with the marks on the cam sprockets, even if both links are say 2 or so links ahead or behind the marks on both, as long as they are both the same you should be OK. If both line up, then pull the timing cover off to see if the third link lines up accordingly with the crankshaft sprocket.

I know it has been mentioned and your stated that the coil packs were new and they are receiving a signal, but have your tried to physically move the coil packs to a different cylinder? If not I would try moving the 2 & 3 cylinder coil packs to cylinders 1 & 4 along with the respective spark plugs. If the misfire moves to different cylinders you can narrow it down to a spark plug / coil pack combo(s). Also, you stated that this is a different engine, have you performed a crankshaft relearn? Basically calibrates your crankshaft sensor which plays an enormous role on mis-fire detection (detects instantaneous angular acceleration and deceleration to determine if a cylinder has indeed fired off.) Just my thoughts, hope they help!

Edit: have you tried to see how it runs with the MAF sensor disconnected (assuming their is a VE calibration)? Just want to rule out intermittent airflow / transient airflow issues.

So I have yet to try swapping the coil packs and plugs around, yet... my buddy is going through some stuff right now and he has his scanner that will be able to read where the misfires are coming from. When it throws a code its just P0300 but were clearly able to see cyl 2 and 3 had something going on.

This is a different engine. I thought the only time you would need to do a crankcase variation relearn is if it is throwing a code for it? Not sure, but it has crossed my mind.

As far as a VE tune. i highly doubt that ZZP does a VE tune in their "canned" tune, unless otherwise stated from them or somebody else. So, no i havent tried that. Thats a good point though. Could help rule out a faulty MAF i suppose..... Thanks for the input. Ill keep everybody posted as i find out. This should be a good reference for people to look back on.... hopefully lol.

Crank relearns are recommended whenever you replace the crank position sensor. A new ECM will automatically run through a bunch of learns on first start. However, these learns occur on the production line. If you have access to HPTuners it takes all of 5 seconds to perform.

Interested to see what the culprit ends up being

Well its not the coil packs, just thought id update everyone. Ill either have to find somebody that has HPTuners or take it to the dealer for a crank relearn.

I have HP tuners.

Man, is there any way we can meet up somewhere and give it a shot?

I'll PM you if youd be alright with doin that.

yeah we can. not sure if you need unlock your vin with my cable to do the relearn but if you do youll just need to pay for the two credits.

You don't have to unlock the VIN, you do the relearn through the scanner

that's awesome. never had to perform one before. any idea how to do it?

I haven't done one on a 2.4l, but on a LSJ it's a bit of a pain in the ass. Car has to be at operating temp (over 170) and then HPtuners prompts you on when to floor it (revs should be limited to ~4500) it's been over a year since I've had to do that