E36 M3: timing problem after head gasket replacement

[stupacshakur]

This problem has been driving me nuts for a while. Had to replace the head gasket on my '95 M3 (got the head machined and valve job while it was off). Got it all back together but I just can't get it to run right. Sorry if this is long winded.

I was very precise when timing it, or so I thought, figured I'd post what's going on to see if anyone recognizes the issue before I pull the valve cover again to mess with it more. I'm a little iffy on how precise I installed the VANOS (I might be a spline or 2 off) but that shouldn't cause it to run this badly right?

Motor runs rich and won't idle (actually I can get it to idle roughly if I disconnect the AFM). Gotta give it throttle to keep it running. Sounds like it also has a misfire. I have already checked everything for vacuum leaks and can't seem to find any issues on the intake end, got all the coils in the right places and made sure the spark plugs are clean. Motor also has good compression.

It is throwing 2 fault codes, one for the O2 sensor (probably to be expected considering how it is running) and the other for the crankshaft sensor. It seems unlikely that the crank sensor itself could be at fault since I haven't touched it and if it is disconnected the motor won't even start. The other alternative is that I have the timing off (at least no pistons are hitting valves), but I didn't think there was so much room for error considering how close you have to get everything just to put the cam locker on and get the chains on.

Any thoughts?

[AwesomeIsLuke]

Crank sensor isn't very unlikely, these symptoms all would come from a bad sensor. Perhaps it is just a coincidence?

[stupacshakur]

Yeah, I'm trying to narrow it down between an fuel injection/ignition timing issue and valve timing, but I suppose it could be a bad sensor. Too bad they are so damn expensive, I'm not sure how to test it, I was thinking of checking for voltage on its pins on the ECM, but I figured it'd be futile since it must at least see it to start, so I'm not sure what would indicate that it is on the fritz. Maybe I'll move all the cooling shit out of the way and get a better look at it before buying a new one. Its been a while since I did the valve timing, is it possible that I timed the motor with it at 180 degrees tdc or something? I would think that would cause interference but, I don't know, I'm trying to think how I could have gotten it this wrong without damaging anything.

[Balthazarr]

Yeah, I'm trying to narrow it down between an fuel injection/ignition timing issue and valve timing, but I suppose it could be a bad sensor. Too bad they are so damn expensive, I'm not sure how to test it, I was thinking of checking for voltage on its pins on the ECM, but I figured it'd be futile since it must at least see it to start, so I'm not sure what would indicate that it is on the fritz. Maybe I'll move all the cooling shit out of the way and get a better look at it before buying a new one. Its been a while since I did the valve timing, is it possible that I timed the motor with it at 180 degrees tdc or something? I would think that would cause interference but, I don't know, I'm trying to think how I could have gotten it this wrong without damaging anything.

180 out of phase and that engine would pop and fart very loudly.
It is possible since the crank requires 2 turns for each cycle.
There are timing marks on the block and the damper.
With those marks aligned and the 1 piston at TDC the valves should be fully closed for that cylinder (compression).

[stupacshakur]

I have a hunch that is my problem, Balthazarr, just wasn't sure, I was a tad hasty after I got the head on and much of the work was a blur, I only remember putting it in TDC, turning it 45 degrees so I could put the head on without hitting a valve and putting it back 45 degrees to get TDC in cylinder 1 then I through the chain on and went from there, I bet it wasn't aligned with the marks. Thanks, wasn't sure if that was a possibility, now it seems the most likely issue. Looks like a I have some more work ahead of me, thanks!

[stupacshakur]

Well, I pulled it all apart and remember how I did the timing. I couldn't find the 0|T marking on the vibration damper before, it was not where the manual said and I couldn't find any info anywhere. After about a hour of searching with a mirror I finally found it on the front instead of on the top, lined it up and checked it against the cams, it was pretty close, but a tad off so I re did the chains and put it back together. It sounds better, but it hasn't fixed the issue.

I'm going back to checking for vacuum leaks, gonna pull the intake play around with the hoses. The sucker is still backfiring though, so there could be something else wrong. Looks like this is going to continue to be a learning experience...

Edit: forgot to mention that it no longer is throwing any codes, I've run it for probably 5-10 minutes so far, still won't idle though as before.

[Tracker5950]

Hello,
Our 98 325i kept giving us the crankshaft position sensor code when the real problem was that one of the four leads (wire) going to the 0xygen sensor was broken. Once soldered back together (careful of the fuel filter/line) and now the car runs fine and shows no codes.
Tracker5950

Also, when you went to time the cams to the engine (at TDC), did you use the tensioner tool and tighten the bolts on the intake cam gear first and leave the exhaust cam gear bolt finger tight (and the secondary chain tensioner loosened with a wire or special tool)? When you do this and release the primary chain tensioner tool, the timing chain should turn the exhaust cam gear to the correct position for tightening. It says this in Bentley but is easy to overlook when you have so much on your mind with the VANOS.

[stupacshakur]

Hello,
Our 98 325i kept giving us the crankshaft position sensor code when the real problem was that one of the four leads (wire) going to the 0xygen sensor was broken. Once soldered back together (careful of the fuel filter/line) and now the car runs fine and shows no codes.
Tracker5950

Also, when you went to time the cams to the engine (at TDC), did you use the tensioner tool and tighten the bolts on the intake cam gear first and leave the exhaust cam gear bolt finger tight (and the secondary chain tensioner loosened with a wire or special tool)? When you do this and release the primary chain tensioner tool, the timing chain should turn the exhaust cam gear to the correct position for tightening. It says this in Bentley but is easy to overlook when you have so much on your mind with the VANOS.

Thanks for the info Tracker, could be, but it isn't throwing the codes like before so I doubt it is on the 02 sensor, but good to know if it starts throwing them again. I used a small hex key to keep the secondary chain tensioner down and did it as it said in the Bentley manual, tightened the intake nuts first then put the VANOS on engaging the first spline using the VANOS turning tool because my model has the spring plate then tightened the exhaust cam bolts. Perhaps I just have a bad AFM, it runs better with it disconnected thats for sure. I'm as perplexed as ever, worse yet the Saturn I've been borrowing from my boss had it's starter go out again so I am totally car-less and can't even work on the M because it is at a buddies place that room on his property and I can't get over there till the starter gets replaced. C'est la vie.

[Tracker5950]

When you say "no longer throwing codes," you mean that you turn the key to light up the dash and pump the accelerator pedal all the way down 5 times quickly and are getting the flashes 1-4-4-4?

Are you sure your air flow sensor (large knurled knob on air box) is screwed all the way down? Are all the electrical connections associated with the air intake to the throttle body fitted correctly? Do the wires comfortably attach to the ignition coils (what you are describing could be a firing order error)? Check also that the vacuum hoses to throttle body are fitted well and not cracked. Did you reattach the fuel injector ground wire to the front of the VANOS cover engine lift bracket? Good luck!

[stupacshakur]

When you say "no longer throwing codes," you mean that you turn the key to light up the dash and pump the accelerator pedal all the way down 5 times quickly and are getting the flashes 1-4-4-4?

Are you sure your air flow sensor (large knurled knob on air box) is screwed all the way down? Are all the electrical connections associated with the air intake to the throttle body fitted correctly? Do the wires comfortably attach to the ignition coils (what you are describing could be a firing order error)? Check also that the vacuum hoses to throttle body are fitted well and not cracked. Did you reattach the fuel injector ground wire to the front of the VANOS cover engine lift bracket? Good luck!

I am using a code reader tool that plugs in under the hood, I'm no longer getting fault codes. The air flow sensor is screwed down all the way and all electrical connections hooked up correctly (there is only 1 on the intake itself). I've I'm positive I have the coils hooked up right. I did reattach the fuel injector ground. I'll carefully recheck everything asap though, thanks for the help.

[Tracker5950]

Hello again,
The only other suggestion I have is to consider changing the O2 sensor (I think your car only has one) and try starting the car (particularly as you said it was rich and it threw an 02 code before).

[stupacshakur]

Thanks for all the posts guys, I finally found the problem. Always seems to be the simplest thing, turns out I was just a moron, while removing the intake the other day I discovered a fitting socket in the intake I'd clearly forgotten about, after fishing around I found a hose with the fitting and plugged it in. Problem solved, car runs like a dream now, it was odd that it was throwing the knock sensor codes after the initial test drive because the motor sounded great, but after a few more drives the codes cleared and everything is copasetic now. Can't believe it, rebuilt the head in a week, and the car was down for a month because of a stupid vacuum fitting.

Anyways, I appreciate all the suggestions, just turned out amateurishness was at fault. Thanks.

[Balthazarr]

Thanks for all the posts guys, I finally found the problem. Always seems to be the simplest thing, turns out I was just a moron, while removing the intake the other day I discovered a fitting socket in the intake I'd clearly forgotten about, after fishing around I found a hose with the fitting and plugged it in. Problem solved, car runs like a dream now, it was odd that it was throwing the knock sensor codes after the initial test drive because the motor sounded great, but after a few more drives the codes cleared and everything is copasetic now. Can't believe it, rebuilt the head in a week, and the car was down for a month because of a stupid vacuum fitting.

Anyways, I appreciate all the suggestions, just turned out amateurishness was at fault. Thanks.

The airbox coolant temp valve that's connnected to the TB?

[stupacshakur]

I'm really not sure, there was a sensor that went into my airbox, I zip tied it out of the way when I removed the airbox to install a cold air intake. Never had a problem with that. It's on the far back corner of the intake away from the motor, no idea what it is for and couldn't seem to find it named in any diagrams or mentioned in my manuals. It is a very small thin, single hose with a plastic fitting that snaps in.

[Tracker5950]

Glad to "hear" your problem worked out. Appreciate you posting the results. If you handled the head, you're not exactly an amateur. All the best.