Autocross in the morning and the car wont run. please help!!!

[lateracer]

A cold compression test can be way different on an older engine; so I wouldn't buy it as a solid diagnosis quite yet. Since you've got it all apart, may as well do a wet compression test (same test with a teaspoon of 30 wt in each cylinder). If the wet test brings up the pressure significantly, that points to bad rings. Unchanged low pressure points to valves.

[Syncro325is]

well just got around to doing a compression test. I had the ignition system off already ,from looking at the timing, so I tested the motor cold. I know it wont give me accurate readings, but what I was looking for was a major difference in pressure, and well I think i found it... #6: 150 #5: 100 #4: 150 #3: 145 #2: 125 #1: 145 soo yeah it seems as though cylinders 5 and 2 have officially shit the bed. What should I do now? I don't see anything abnormal with the valve cover off and the valves seem to go up and down just fine.

[Syncro325is]

Hmm cam timing, or a sticky/bent valve

maybe?

Cam timing is good...

[SpecM]

Hmm cam timing, or a sticky/bent valve

maybe?

[Syncro325is]

Here is a link to a video i made... Its not optimal because there is music and video from the autocross, but I don't want to upload another video. maybe someone will know what is wrong by the sound. idk i figured it may help. You can hear the sound my car is making past the video. Mines the black e30.

http://www.youtube.com/watch?v=zzVHpfSmI7M

[Syncro325is]

Anyways the timing belt apparently is not the problem. Onward to harbor freight to get a compression tester...

[Syncro325is]

It would be a help to know what car this is. If one with an M20b25 engine (325i/is) I'd suspect the CPS, harmonic balancer, or something that is interrupting power to the DME.

right, its an 87 m20b25 swapped into an 86 325es.

[jlevie]

It would be a help to know what car this is. If one with an M20b25 engine (325i/is) I'd suspect the CPS, harmonic balancer, or something that is interrupting power to the DME.

[Syncro325is]

could also be timing i suppose, the t-belt could have slipped a tooth or something

Well I did do a T-belt recently, when I did my refresh. I was under the impression that because the m20 was an interference motor the valves would hit if it were off even the littlest.

BTW autocross was freaking awesome! I didn't get to drive my car, but I took Ricksloans 335...Yeah doggy!!!

[Danny]

I didn't actually know what to do.

... I just wanted to say yeah doggy.

[RickSloan]

no o2 doggy...

[Danny]

Unplug the o2 sensor and run that fucker open loop.

YEAHHHH DOGGY!

[Adrian_Visser]

could also be timing i suppose, the t-belt could have slipped a tooth or something

[Syncro325is]

no offense, but I really hope you're wrong.

[Adrian_Visser]

Backfiring like that means unburnt fuel is going out the exhaust, I would do a compression test to see if there is a dead cylinder, even if it is still firing on all cylinders the compression could be low enough to not completely burn the charge and send it out the exhaust.