:confused3

 

Am I missing Distributor Cap & rotor? :3:

 

No, but I was. Inspected both, light burn marks on cap electrodes, rotor in good shape, no signs of arching in cap, clean and dry. New cap and rotor coming, I am starting to throw parts at it.

 

crank sensor? connector? wires?

Cam sensor? connector? wires?

Also check the crank hub main crankshaft bolt that it is tight and the hub has not spun causing the hub to be misaligned and not reading on the sensor correctly. Happened to mine and drove me nuts forever until i figured it out from a board member. I see you're in Tampa...i am in Saint Pete good to know theres another e34 M5 owner near by thought i was the only one besides another buddy of mine in ft.lauderdale.

 

Hi Rob , this must be driving you crazy after putting so much time and effort into your beloved M5 .

Has the efficiency of the idle control valve been checked ?

D

 

Mike, actually I am in Safety Harbor, I just use Tampa for the regional aspect and it's where I work. Crank sensor has proper resistance, the gap is set properly, the wires check good from the sensor plug to the DME terminals.

With all timing aligned the #1 piston is TDC so I think that means the hub hasn't spun.

The cam sensor is the coil around #6 spark wire I believe. I get 5v to plug and I read continuity on the other 2 wires but specs say I should read 80 ohms. I checked the old coil and it reads the same as the new one, .000 on 2K ohm scale

 

How would I check that effiency David? I did the resisitance check described in the manual and I get the correct ohm readings at the pins when tested at the connector near the fuel rail. I visually checked its cleanliness and operation. I have a new one coming and will swap it out anyway. I am breaking out the shotgun and check book to get this resolved!

Keep the ideas coming folks, thanks, Rob

 

Hi Rob, My car had similar problems after having a lot of gaskets replaced, it then failed its MOT on emmissions. Apparently it was running very rough. Thankfully it turned out to be a rocker gasket leaking quite badly, which when fixed solved the problem. My car is a 3.8 though, but I can't see this making a difference in this case. Hope this helps and good luck.

 

I had a similar situation recently with my '91 Audi 200 quattro...very different car, I know, but some concepts carry over. After weeks of these issues, MANY hours of diagnosis work, and a few key sensors being replaced, I swapped out the ECU with one that was known to be good. problem solved. If you're within a few hours drive of another E34 M5 it may be worth your time to meet up and do a quick swap.

 

I hear ya. That is something I am considering, anyone out there want to sell me a spare?

I asked Kevin at Injection Labs if he knew of a company that could test mine, he did but suggested it's hit or miss with the quality of their testing. I'll keep throwing parts at it till I have no other choice.

 

hey Rob, i would sure try to exchange ECU´s....

 

You wrote that the lambda doesn`t flash fault codes, but have you changed it?
as MAF and lambda work in a loop the symtoms could be explained by a failing lambda sensor. It isn`t uncommon that a faulty/failing lambda does not throw codes altough it has gone bad. Worth checking. Correct plugs used?
TPS?
:cheers:
good luck
Sakke

 

Dr, when I had it on a scanner the o2 sensor cycled between .2 and.9 volts about every 4 seconds. I have the proscribed Bosh plugs with the proper gap, just changed as part of the "ISOLATION PROCEDURE".

I thought I might have found the problem. A busted relay pin 87 on air pump relay! No such luck , put in new one, no change.

I have a new o2 sensor, TPS, ICV, Cap and rotor coming. All vacuum lines fresh from a year ago when I replaced them. I am so screwed. I am afraid it is going to be something so obvious it will be embarrasing, but I'll own up to it if it is.

At least I am gaining a great deal of understanding about the motor controls.

Do you know how the changeover valve II works? Does the valve energize to allow vacuum to open the air pump valve?

How is the clutch on the air pump actuated. Guessing 12v from DME for X amount of time. Just wondering what the symptom of terminal 87 on the relay would present itself. Terminal 87 is switched to contact term 30 and delivers 12 v from Power distribution terminal 30 to changeovervalveII. The ground to actuate the relay solenoid is provided by the DME terminal 23, a tansistor actuated ground.

Anyone have any idea of how the DME ground is supplied? Based on engine temp or just a time delay?

 

Rob, in trying to find a misfire on mine we eventually came to the conclusion it MUST be the DME.

Removed it from the car and sure enough - there was a burned out transistor on it.

I sourced a 4.0 V8 DME from a breakers yard and they all shared the same components, so we were able to steal a transistor from it and solder it to my M5's DME.

It is easy to remove the DME, open and inspect it - you never know!

Good luck :confused2

 

That is my last step. Not an electronics guru. Have friends who are. How did you ID the faulty transistor?

I am beginning to suspect the circuit that drives the IAC.

See if this makes sense. I have the intake plenum removed, o2 sensor diconnected, maf unplugged.

I can observe the IAC opening.

Turn the key on, the valve closes completely, try and start the car and it goes full open and stays there, engine stumbles and wont start.

Disconnect the TPS plug, turn key on, IAC goes full closed, turn to start and valve opens about 1/3 and car starts and idles at proper rpm. A little rough from the o2 and maf and plenum removed.

The throttle response doesn't bog down and it seems to run fine.

I checked the TPS adjustment, it shows continuity when throttle at idle, open circuit when throttle moved and continuity at WOT, all at appropriate pins.

So just for the hell of it I adjust the TPS so there is no continuity at idle, hook it up and the car starts and idles fine.

I know I can't leave it there and risk lean fuel at WOT and all the bad things that can happen in that condition.

With the TPS plug disconneced and the engine running I read

5v pin 6-4
4v pin 5-4


So, I am taking votes on which component is bad

1. IAC

2. TPS

3. DME

 

That is my last step. Not an electronics guru. Have friends who are. How did you ID the faulty transistor?

Just to close this off, even though it doesn't appear to be the problem, we are not gurus either - the fault transitor had clear scorch marks on it from when it popped!

 

Running an aftermarket chip?
Did you try leaving the battery disconnected overnight?
Motor compression tested ok?
Did you check fuel pressure under load?
Bad (wet) plug?
Definitely double check ignition components (new parts don't mean they work 100%... sux but it happens).
Hell it could be a myriad of factors... so go to the obvious and cheapest first (old school troubleshooting sometimes works better than computers!), probably saying things that you already know... but I hope it helps some.

 

Hate to say it, but my vote goes to DME. If you can't find a local to try a swap before buying another, replace the ICV first cuz it's cheaper...but you knew that. Problems like this make mecherrsagai

 

What makes the motor run rich at 600 RPM?

TPS - it's delivering an idle signal to the DME so that's ok. ICV transistors - maybe..

Throttles Sync'd. - If the air bleed screws are closed up, not enough air will flow through the ICV and it will run like a pig. Make sure they are open at least 1.5 turns from closed.

IDLE screw - Make sure it's not fully closed.

Fuel Pressure Regulator - it needs vacuum at idle to reduce the fuel pressure. IF the vacuum is not there, pressure will be high and it will run rich.

DME sensor - blue temp sensor. Remove the plug, idle should jump.

Crank sensor, Cam timing (things I don't know much about).

Not an M5 expert but this is where I would look.

 

Dave, great suggestions. I am hoping beyond hope I found the problem, the TPS switch.

Everything I have read, and the schematics confirm this, is the S38B36 TPS switch is just a make and break contact switch.

This is what I have found, got the new TPS switch today but it has the 3 prong rectangular connection. Mine is the round plug where pin 4 is ground, pin 6 is idle and pin5 is WOT.

Damn, they sent me the wrong part. So I decide to test the new switch function. At idle I have continuity, throttle open no continuity, WOT-continuity, works as advertised just wrong connection.

So I take my old one that I had tested only at the DME terminals, and test it again.

At Idle I read 3 ohms and as I move the switch towards WOT I get a decreasing resistance till I get to WOT where I read continuity with no resistance. Acts like a rheostat to me!

Could it possibly be the previous owner installed a S38B38 TPS and I never realized the car ran sub par.

With all the tune up work I had done did it raise its ugly head?

Is this a symptom of a malfuntioning but correct TPS?

Any one reading this that can confirm my suspicions please chime in.

This could very well explain why the ICV was acting wacky, it was being pulled in 2 directions at all times till WOT.

 

Sadly not. The tps will have an idle contact - can you hear it click? You could always short the plug to provide a simulated contact

The DME has a number of compensation tables that rely on an idle signal regardless of TPS type.

I've just been through all this with my E30 M3 and the cause

 

seem to have deleted stuff.

The cause was a split vacuum hose to the idle screw housing to ICV and FPR.

Bad ICVs fry the DME transistors so have you checked the resistance of the ICV pins? Outer to middle should be 20 ohms both sides and outer to outer should be 40 ohms.

 

Dave, the idle pins ohm out to spec. I opened the DME and could not smell or see any burned components or faulty solder.

Should know this week end if this is the problem.

 

Hi - what was the outcome on this?

 

Turns out, some time in the past, some undocumented work was done to the motor. A 3.5 liter crank shaft was installed in the car. I had to remove the hub, redrill it, reindex it and reinstall it so the timing realigned. It runs fine now, minus .080 in of stroke. I found a good used S38B36 crank and some time in the near future will rebuild the motor. No where in the extensive maintenance and repair records was this documented.

I found a machine shop here in Tampa that does high end machine work for F1 and other racing circuits. The cost to machine the block, balance all rotating parts and blue print the engine is 1,800 USD. Guaranties the motor to 8,000 rpm.

 

So the root cause was the base timing being incorrect due to TDC sensor picking up wrong timing?

 

That is correct. Some one had moved the pulse sensor to pick up TDC, when I moved it to the correct position it ran like crap. I had to redrill new holes in the old hub (incorrect type) so balancer would be indexed correctly. I ordered a new hub prior to finding the problem suspecting the woodruff key being broken. The hub I received did not match the hub in place. The correct hub uses a bolt, the one on the car secured by a nut. Some research lead to discovering an incorrect crank. The only difference between the 2 cranks is. 1. Index for TDC different, 2. Hub attachment different, 3. Stroke .080 less on 3.5 crank, 4. Oil seals diffent sizes. Main and rod bearing sizes are all the same.