cyl 1 low compression, misfire, out of nowhere. can't find the problem.

[wakeboardr42393]

Hey all, I bought an 87 325is about a month ago for cheap, and towed it home. I have great and reasonable suspicion that it had been sitting for a long time, even though the P.O. didn't say that. I put new fuel lines in it, changed the oil, checked all the fluid and topped off as necessary, and it started right up. :o great! but when I went to try to press the brake pedal, i heard a line pop and felt the pedal drop. great... :( haha. so, down came the subframe and related, in went new brake lines, bushings, axle seals, etc. Just 2 days ago I got new pads and rear rotors (old ones were toast) and installed all of this, bled the brakes, and took it for a drive. all was good, with the exception of some minor unrelated things- sweet! :)this morning, I did a few other adjustments, then drove it to the license and title places to get the title transferred and get plates.

I was excited that I was finally ready to drive this thing! The engine was running good, besides for valvetrain ticking as it had since my 1st start(my 1st bmw- i'm told this is normal on these engines) I had it on the highway and gunned it on the on-ramp, and it ran and pulled great! ok I get my title. Gettin on the highwayagain, to go get my plates, and I hit the gas maybe about 3/4 throttle to (quickly) get to highway speed. As soon as the auto trans downshifted, the engine immediately started misfiring. It was still driving, with no new noises besides the misfire, and easily held highway speed, so i drove to get my plates and then back home.

The misfire was still there after i got home and re-started multiple times. I located the misfire to be at cylinder number one by removing each spark plug wire individually at idle; wire one removed made no difference in idle, all the others did. ok. took out spark plug. cleaned, gapped, checked for spark. positive on spark. put the plug back in, but the engine still misfiring. moved on the the fuel injectors. I swapped injectors between cylinders 1 and 6, cleaning them and adding new top o-rings in the process. started back up and the misfire is still there, and still on cylinder number 1. so the fuel injector is not the issue. There is power at the connector for the fuel injector, and the connections are clean. I then switched the cyl 1 and 2 plugs and wires, to no avail. checked the coolant for oil and none. still missing on cyl 1. so, i did a compression check. dry and wet on the problem cylinder, and only dry on the others. the engine was cool, but not completely cold. results as follows:

1: dry-60psi wet-110psi
2: 140psi
3: 125psi
4: 137psi
5: 135psi
6: 141psi

I'm fine with the rest of the cylinders' compression results. Again the misfire is consistent and localized to the cylinder 1. the engine is making some pretty loud (to me, used to other more modern cars) valve train noise when running, but i was told this was normal.

I'm thinking either a broken head gasket, leaky valves (could this happen if they are severely out of adjustment from the car sitting?), broken rocker, or a broken piston ring. I don't see why anything else would happen all of a sudden like that, when the engine was running fine before. (suggestions welcome) And i'm hoping the block is not damaged . The cars still runs and drives. just not as well (obviously).

Where should I go from this point? should I just dive in and start taking things apart? should I continue to drive the car like this? will it possibly get better?Any responses, stories, comments, suggestions, teases, or anything else is welcome! I'd like to get this thing going! Thanks!:pimp:

[jlevie]

The first thing to check would be the rockers on cylinder 1.

[wakeboardr42393]

The first thing to check would be the rockers on cylinder 1.

Good suggestion. thank you! I had a peek at the rockers through the oil filler hole, the exhaust seemed to be fine and the intake was kinda hard to see but kinda moving(less than the exhaust).

tomorrow morning I will take the valve/rocker cover off, and post my findings.

[wakeboardr42393]

well, this is a relief (i think)

I think i found the problem :roll:










how does this happen? lol

[dwight]

Just old

[TobyB]

weak valve springs. Overreved. sticky valve guides. voids.

aliens.

Karma. Carma. Carmex.

t

[jlevie]

I've seen enough broken rockers on engines that seldom, if ever, saw the upper end of rev band and were never over reved to have formed a theory about rocker failure. I think that a history of failures to adjust the valves on schedule (every 15k) is the primary cause. The repetitive impact from excessive valve clearance leading to eventual failure.

Broken rockers when a timing belt fails or from a serious over rev are to be expected.

[wakeboardr42393]

I've seen enough broken rockers on engines that seldom, if ever, saw the upper end of rev band and were never over reved to have formed a theory about rocker failure. I think that a history of failures to adjust the valves on schedule (every 15k) is the primary cause. The repetitive impact from excessive valve clearance leading to eventual failure.

Broken rockers when a timing belt fails or from a serious over rev are to be expected.

Yeah, I thought the same thing. I didn't think about the over-revving, but Its a good possibility that the clearances were far out of adjustment.

do these engines not have rev-limiters?

[lcoleman]

The rev limiter isn't going to do much good if you money shift into 2nd instead of 4th under load.

[wakeboardr42393]

dissassembly, part I

so, I started taking things apart to get the rocker shaft out, It wasn't as bad as everyone made it seem. I used a manual and the following thread as a guide: http://www.e30tech.com/forum/showthr...t=rockers+head When i did it, it was pretty straightforward with no major issues in my case.

well, to start off, I removed the spark plug wires from plugs, and the valve cover. I then removed the distributor cap, and unpluged the main wire from the ignition coil. I took off as many coolant hoses as needed from the front to make everything easier to work with- more room etc. The cap and wires were just laid back over the engine out of the way.





Next, I removed the cooling hoses from radiator (forgot to drain it- woops. lol) and I attempted to remove the atf cooling lines from the rad as well. I got the top atf line removed, but couldn't get the lower atf line removed. the entire threaded peice was just spinning in the rad. So, I just cut the rubber part of the line so I could get the rad out. **** happens. It will be easier to work with when it is out of the car. the rad is held on by two clearly visible bolts (from the engine bay) on top, and just lifted out of my car once everything was disconnected.

Seeing how the AC system had ZERO pressure whatsoever, I didn't even bother being careful with that stuff, it looked like it was in bad shape. After unsuccessfully trying to unbolt the ac rad, I just cut the lines, pulled it out, and moved on. I can do without AC .



At this point, It looked like I had plenty of room. The power steering belt is off in the pic, but I don't think it even needed to come off.



The alternator belt does need to come off, and the bracket needed to be loosened on my car to easily remove the upper timing belt cover, after the rotor was removed.

[wakeboardr42393]

The rev limiter isn't going to do much good if you money shift into 2nd instead of 4th under load.

yeah, that's always a possibility with a manual trans, lol. I like how you put it.

[Cabriolet]

wow i feel so bad for you guys in the rust belt. I've never seen so much rust/oxidation in an engine

[wakeboardr42393]

dissassembly, part II

The timing marks were lined up to the marks on the block, and all of the rocker arm clearance adjusters were loosened and opened up to maximum clearance. After this, cylinder number three's intake cam lobe was near maximum lift, therefore making the rocker arm under the tension of the valve spring. so, I turned the engine a bit, so that the #3intake and exhaust valves were closed, loosened both, and slid both of them over towards the front of the engine, to clear the intake cam lobe. you can se in the photo, the top is the intake side and bottom is exhaust side, and timing marks are lined up.



now, all of the rocker arms were lose, and I read somewhere that the rocker shaft could be pulled through holes in the cam sprocket. So, I removed the torx-head bolt from the cam sprocket, and the rotor-mount and this plastic disc both came off, the sprocket stayed on. I bolted the rotor mount back in place to hold the sprocket in place and steady. you can see that the shaft has enough room to go through the spaces in the sprocket.



After everything was loose and ready to go, I oiled up my shaft with my handheld pump oil squirter filled with 40 motor oil. I stuck the blade of a big flathead between the back shaft end and the side of the head. the shaft started moving fairly easily.


After there was no more room to pry from back, I took some locking pliers and clamped them onto the shaft, with a folded up rag over the shaft, to not mar the shaft surface. you could probably get better grip if brass was used, as i saw in another post. but my shaft was't extrordinarily tight as others' apparently were, and it spun with only slight effort.



I just twisted and pulled until it got stuck on the gunk, and lightly tapped the shaft back in with an extension, and started over again, in and out repeatedly, each time coming a little further out before gettin stuck.



Once the front end of the shaft cleared the sprocket, things got simple. I used the small locking groove in front to put a flathead and lightly tap, along with the vice grips now at the tip to twist and pull. Every time the shaft cleared a journal or rocker arm, I could pry from the back with my big flathead (prying was the easiest way to push it.)



the further it got out, the less effort it took to move the shaft. when it was about 2/3 of the way out, i just grabbed it with my hands and a rag, and pulled it out by hand. it wasn't hard.



Now to wait for the replacement parts, clean some stuff up, and back together it goes!


i know i left a few obvious things out, i just wanted to give an idea and some pics for anyone interested.

[wakeboardr42393]

wow i feel so bad for you guys in the rust belt. I've never seen so much rust/oxidation in an engine

Tell me about it. Salt is the root of all (car-related) evil. i hate it lol. I was living in california for a bit and it was surprising to me how non-rusty all of the older, neglected cars looked. Here, cars just fall apart from rust after time, if they are driven in the winter. grr.

[Cabriolet]

change your TB it's worn. when they get shinny that means EOL