'86 325iC Stalling issue

[DigginMyE30]

Stalling issue has gotten progressively worse.

1986 (mfg. 7/86) 325i German import Euro model convertible.

A little back story; I purchased the car August 2013. The previous owner bought the car in British Columbia, Canada in the fall of 2012 and drove it back to Manitoba and flipped it within 12 months. I drove the car till the snow flew here in Winnipeg, Manitoba up in Canada. I put on about 1200+ kms (745 miles) in 2 months. Not much history but drove like a champ, a real driver’s car. The only issue I had last fall was a right wheel bearing started whining. I was going to park the car over the winter and do the bearing and some other maintenance items. With a record snow fall this winter I didn’t get the vert from my garage to my shop so I decided to wait until spring to begin with the repairs. Got the bearing changed without any issues and drove it for a week before I decided to start on the rest of the list. Went out on a week night and changed the plugs. I purchased Bosch SuperPlus plugs (WR8LC+) through a local parts supplier and pulled out the old Bosch Plus 4’s.

With weekends getting busy I decided to drive the car for a couple weeks till I had a free weekend to do the timing belt and water pump.

That’s when the issues began. One day driving home from work the engine cut out, just died while driving 60kpm (37mph). I turned the key off, saw tach bump after a couple of seconds, turn the key and started up no problem.

Next day, again driving home in the afternoon, car stalled at an intersection, started, drove a bit and stalled again while driving. It would crank but not start. After waiting a minute or two it started like always.

Next day same deal, afternoon/ early evening with nice temperature outside, not cool, not too hot, car died, restarted, died, & restarted. It would stall while driving or coming to a stop at the intersection. Sometime it started right away, sometimes after waiting. Weird thing is and it might be totally unrelated, sometimes after turning the ignition off, waiting for the tach bump, then turning the from off to on to off 5 or 6 times without actually going to the start position on the ignition, it would then start like it never had a problem. It would still stall after driving a bit.

The car is now undrivable. Stalling has become progressively worse. Will start up when cold and idle for a couple of minutes then stall. Will start and if I try to drive it will stall after a 100 meters.

I have purchased a Bentley manual and have been going through a number of the trouble shooting step to no avail.

I’m not a mechanic but I am fairly mechanically inclined so I started looking through the forums for some guidance. Checking for vacuum leaks at all the usual locations was suggested so I inspected the intake boot & hoses for cracks, but could not see anything obvious.

So here is the list of things I have attempted to this point:

New Parts:
· Spark Plugs
· Fuel Filter
· Fuel Pressure Regulator
· Crank Position Sensor x2
· Coolant Temp Sensor (blue)

Known good used swap:
· Air Flow Meter
· Coil
· Plug Wires
· Main relay
· Fuel Pump Relay

Tested:
· Throttle Position Sensor – Idle & WOT continuity tests OK
· Fuel Pump – Operational
· Transfer Fuel Pump – Operational
· Fuel supply – Volume of 40 oz. in 30 seconds (higher than spec)
· Compression – 175-190 (high?)
· Coil resistance

I’m not sure what to do at this point and don’t really want to have it towed to the dealer since I am 80km from the dealership and don’t want to pay the $120/hr. rates either.

Any help would be appreciated.

[dnguyen1963]

The only good way to find vacuum leaks is smoke test. Since you do not have access to a shop, I would DIY a smoke machine. Plug both intake and exhaust before you pump in the smoke. Try to keep the pressure around 2-4 psi to find all the leaks.

[NoM54me]

How did you test fuel pressure? If it was anywhere in the line before the pressure regulator, that part could still be bad even though fuel pressure looks good. However, if by "stalling" you mean the engine just completely shuts off but otherwise runs fine, the OBC relay may be bad. You said you have to fiddle with the ignition switch a bit sometimes to start it, the OBC relay is part of the ignition circuit. It's a black box usually located by the hood release lever. Remove the connector, then cut the green and green+red wires from the connector. Then, splice those two wires together, not on the connector side though! You've bypassed the relay. This fix does NOT affect the operation of any parts on the car, except for the "code" function of the OBC, even if the OBC otherwise doesn't work. It interrupts the signal from the ignition switch to the ECU, and is the very obscure cause of many starting problems. Try that, let us know what happens.

[DigginMyE30]

My vert is still not running.

I have now changed the distributor cap and rotor; the cap probes were all pitted. The old rotor ohms tested at 1000 but I changed it anyway. I also put on a new timing belt and water pump while I was in there.

I retested my old CPS sensors and the new ones I purchased. The old ones tested at 944 & 932 ohms while the new sensors tested at 858 & 852 ohms. The Bentley states that 960+/- 96 ohms is spec so the new ones are out of spec.

I haven’t attempted a DIY smoke test but I’ve visibly inspected the vacuum line but don’t think this is the root of the problem.

I have fuel but no spark. Well occasionally I have spark.

I have tested and tried both the coil from my ’86 vert and the coil from my ’89 IX. No difference. Both had .7 ohms across 1 & 15. Resistance across 4 & 15 is 5380 and 5440 ohms respectively.

I tested for spark last night and found none. This morning I retested and there was spark. I put the HT lead back on the distributor and she started up, ran for 15 seconds, died and wouldn’t restart. I retested for spark on the HT lead and again, nope. Voltage is present on coil pin 15 during start condition, which I verified with my test light.


My ’86 has the following 32 pin DME:
325i/ECE E30 M20/B25 (171hp) 85-87 0 261 200 081 Bosch Motronic M1.0

I ran through the Motronic control unit electrical test as outlined in the Bentley manual. Results as follows:

• Voltage supply>>Pin 18 does not have contacts, battery voltage at pin 35
• Main grounds>>Continuity on 5, 16, 17 & 19. Pin 10 has no contacts.
• Throttle Switch>>Pin 2 has continuity with throttle closed,no continuity with throttle half open. Pin 3 has continuity at WOT

• Fuel pump>> Fuel pump runs
• Starter input>>More than 8VDC at start condition
• Engine speed sensor>>944 ohms
• Reference sensor>>932 ohms
• Fuel injectors All activate
• Air flow sensor resistance fluctuates
• Oxygen sensor test not complete

As I was testing the Motronic connection a saw a black plastic box tucked up above the DME. It is spliced into the harness of the 35 pin connector. It is a Gat-Tronic ST 27/1 module which based on what I could find on the internet it is an aftermarket add on for an O2 sensor installation that was likely done when the car was imported into North America from Europe. I need to now inspect the O2 sensor and check for continuity at the 35 pin connector.

I am beginning to suspect that I may have a flakey DME as I doubt that a bad vacuum leak produce the spark/no spark condition?


If you have any suggestions it would be appreciated.

Bryce

[DigginMyE30]

As an update, I had a consultation with Mark from Enhanced Automotive Technology. Sent him a couple of pictures of the PCB's of the DME. He had me take an extra pic of a specific location where the leads of the large transistor that is mounted on the heat sink land on the back side of the board. He spotted a minute crack on one of the leads, suggested that if I was comfortable I could get out my soldering iron and some electronic solder and repair it myself. My understanding is that this transistor drives the coil.

My car is back together and running.