New Guy here, dead cylinder

[e30kawi]

New guy here, this is my second e30. It is a 1990 325i, stock motor. It died on me the other morning on my way to work. I had done all the routine maintenance, t-belt, plugs/wires, etc. I assumed something had gone out of adjustment as I had just done a valve adjustment.

Turns out, the valves were still in adjustment. I tried to start it again, wouldn't really fire up, did once but it was rough/low at about 500 rpm for a second. Exhaust smelled like sweet smelling gasoline and was kind of smokey. Open to suggestions. TIA

I did a compression test.
#1= 160 psi
#2= 158 psi
#3= 155 psi
#4= 125 psi
#5= 35 psi
#6= 155 psi


I thought maybe I had blown the head gasket, but it was rough looking but not blown. Upon tearing into it, the bolt holding the rotor to the cam gear had backed out and was no longer giving it the right firing order. But that doesn't explain the dead cylinder.

Any ideas, Thanks in advance.

[e30mpg]

do a wet test

[craiggroves91]

Are you sure the valve adjustment was done correctly? The 125 psi on cylinder #4 is concerning as well. So at this point you've removed the head?

[e30kawi]

do a wet test

Are you sure the valve adjustment was done correctly? The 125 psi on cylinder #4 is concerning as well. So at this point you've removed the head?

Not sure what a wet test is. Yes I yanked the head already. Going to have it cleaned up, checked out, and resurfaced. Also clean the block, oil seems to have been seeping out from the bottom of the head for a while, it is thickly caked on there.

The car developed a slightly high (1000 rpm idle) that would come at random times. It started with the funky idle about three weeks ago. I did the valve adjustment two weeks ago. The car has never seemed to accelerate as smoothly as my old e30.

I am curious if it is possibly a ring issue, the car didn't smoke.

[jlevie]

It would have been easier to diagnose this before the head was off. After the dry compression test, you should have done a wet test of #4 & 5 by squirting a bit of oil n each cylinder and seeing if the compression numbers improved. That test should have been followed by a leak down test. That combination will usually tell if the low numbers are from bad rings or bad valves.

If the cam sprocket bolt backed out enough to cause a timing error, I'd bet on bent valves being the cause.

[e30kawi]

If the cam sprocket bolt backed out enough to cause a timing error, I'd bet on bent valves being the cause.

Thanks for letting me know of the wet test.

The cam sprocket didn't come loose, just the end with the rotor. There was no evidence that the valves came into contact with the pistons. There was a lot of build up on both the valves and the pistons. Also, the timing marks lined up.

What are the odds that the rings were bad and didn't smoke before the rotor came loose?

[jlevie]

Bad rings usually gradually get worse and don't suddenly fail. But if ring(s) broke, that could happen suddenly, like wise for a head gasket failure. I can't see incorrect ignition timing as being the cause.