Trouble in Paradise---My M50 Won't Run When Hot

[92E34]

I've had my E34 now for 3 weeks and it has developed an interesting issue.

But before I start I'll give you the low down.

M50 Non vanos
5 speed
131,000 miles

I was coming up from phoenix to prescott (a trip all of 90 miles and about 3000 ft of elevation change). When leveling out in prescott at the first light, the idle was a little off. It dropped to about 500 rpm and felt like the engine was hammering. I stopped in an Autozone. Went in to get some parts, came out and......Tried to start it.....I cranked it a few times and got nothing. After a tow home, and a few beers later, I got cocky and tried one last time.

Som' bitch it started! Idling very rough at around 600 I was able to get in into the garage.

I'm thinking its a sensor somewhere.

So here I am Stuck in the middle of nowhere and I need to get back down to phoenix. I think its something heat related.

I need some help quick!

[RobPatt]

... ? got good oil, enough coolent, etc? Otherwise I can think it'd struggle and start after a few more cranks than normal, then stubmle to stay running... but no start I've not a clue... sorry, I think it should run... lots of folks here smarter than me, so hang in there... -Rob.

[GoldenOne]

just throwing it out there...since there was a climb UP to 3,000 feet doesnt that mean the air is a lot thinner and that could play a factor in the air/fuel ratio and sorta straining the engine?

[92E34]

Well I got her to run this morning after 15 seconds of cranking. The she idled a little below where it should be about 100 under. I took off the airbox, MAF, and Tube and noticed one of two things.

The Air take boot is shot and the hoses going to the box are shot. Could this be the problem?

Its running like the ignition has been retarded back, like its on limp mode. I also stomped it and no codes came back.

[632 Regal]

thats what computers are for. fix the intake leaks, with any raw air coming in can cause all kinds of strange problems.

just throwing it out there...since there was a climb UP to 3,000 feet doesnt that mean the air is a lot thinner and that could play a factor in the air/fuel ratio and sorta straining the engine?

[92E34]

Actually Prescott is at 5280 feet above sea level.

Well I made some progress. I fixed the Air intake tube and its not leaking. Then I cleaned the spark plugs and grounds at the coils. But the hammering noise its been making, well its still there, its just less evident. Before I cleaned the plugs it was VERY loud. My mom could hear it in the other end of the house. Now you can hear it in the car. I made sure to torque down the plugs, before they were only in finger tight.

I was looking through the manual and where the heck is the pulse sensor and the Idle sensor?

I'm gonna check the fuel pump later today and change the filter.

[BillionPa]

do a DME reset to adjust to the elevation change, you could have damaged the spark plug by not having it in there properly with oil and exhaust blowby. i would replace all the plugs. the intake leaks could have caused some damage to the engine with silicon particulates, get some molybdenum disulfide oil additive to alleviate it.

[92E34]

Made more progress today.

I went through the sensor list to just double check. Two that I tested came back way out of test limits:Crank position and Oxygen sensor. The CPS is supposed to read 1280 ohms and I tested it at 400 ohms its only allowed plus or minus 10%. The Oxygen sensor had no resistance at the white wires. ground was also disconnected. The CPS also had a lot of gunk on the end of it that was touching the ring.

I'm kinda stuck with the Air boot the way it is. Same way with the CPS, nobody has it up here. I duck taped it and made some progress, its not leaking. Nobody has it here.

As for the Computer, I disconnected the battery for a half hour to clear codes.

[92E34]

Made more progress today.

I went through the sensor list to just double check. Two that I tested came back way out of test limits:Crank position and Oxygen sensor. The CPS is supposed to read 1280 ohms and I tested it at 400 ohms its only allowed plus or minus 10%. The Oxygen sensor had no resistance at the white wires. ground was also disconnected. The CPS also had a lot of gunk on the end of it that was touching the ring.

Whats the Resistance reading for the Cam Position sensor?

I'm kinda stuck with the Air boot the way it is. Same way with the CPS, nobody has it up here. I duck taped it and made some progress, its not leaking. Nobody has it here.

As for the Computer, I disconnected the battery for a half hour to clear codes.

[92E34]

I put the New O2 sensor on it now it takes a whole lot shorter time to start. But its still shaking the whole car.

I'm thinking that I have to change some vacuum hoses due to some sucking noises on the right side of the Throttle Body.

How much of a pain is it to pull the Intake?

[BillionPa]

not too bad, just have all new gaskets or you are screwed.

[92E34]

I removed the intake, changed the Vacuum hoses, cleaned the inside (had about 1/8 inch of grease on the inside), reinstalled the manifold, and now a new problem has arisen.

Found a couple of other interesting problems. The vacuum hose going to the fuel pressure regulator was, how do you say, swiss cheese? It became powder in my hand when I touched it.

It sounds like the engine is now rumbling or missing at idle but as soon as i get it above the 2000 its smooth. Between 750 and 2000 it sounds like a rod knock.

Its starting to drive me up a wall. I am leaving the car in Prescott because I don't need to chance it screwing up on me again.

[92E34]

Well I took it to a mechanic, and well the news isn't good.

Compression is the following numbers 80-75-75-60-120-120

The mechanic said that the head probably needs to be overhauled. So i took off everything, intake, manifolds, and covers and I can see that the valves are not closing all the way.

If anyone has done this job before, Can you give me some pointers?

[92E34]

Well the Exhaust valves on 5 cylinders are bent. The number 4 cylinder they are about 15 degrees bent and I can see where where my low compression is and There are some slight knicks on the top of the pistons.

Does anybody know of a good head shop in phoenix?

Here are some pics:
http://www.PictureTrail.com/gid12753431

[DaveVoorhis]

Did you miss a shift and over-rev it on your 90 mile trip?

[92E34]

No I baby my 525.

I've been raised in a family with european cars where you can't abuse them or they break. We've had a few VW's, a 733i, an audi, and a jag.

Hmm, upon retrospect, the cam gears do look worn, along with all the other gears. Where can I get them new? They are starting to have a double dip, the top of the gears are worn.