M20 questions

[genphreak]

Hey all,

We have an M20 (in an E30) here which has two problems that kinda have me googling tonight. Can anyone out there help out?
This is what's wrong:

1. The engine conks out once the coolant reaches temperature, if you have the AC on. Without AC it runs happily forever.

If you start the car and turn the AC on, it runs fine at the normal 800rpm (stable & smooth but not perfect). Then, once it is just under half way on the temp gauge (6 minutes odd), it just stops dead.

All the fans and cooling system components have been changed or tested operational. New coolant, new timing belt, thermostat, MAF conversion.

Once it does conks out, it won't re-start unless you wait a long time. The starter relay clicks, (but not the solenoid), you can hear the ignition/HVAC components running, the warning and dash lights all come up fine.

- Could this be a return valve problem like can hapen on e34s? I was thinking it to be electrical. The only abnormailty is that the service indicator LEDs flash when you (try) to engage the starter motor. However it only happens when the AC is on.

The car does re-start again, when given time to rest.

2. There is definately an intake leak (though all pipes have been replaced.

If you remove the oil cap, the idle does not change. I suspect the Motronic has gotten used to running on a little 'extra ventilation'. The car misses slightly when driving off idle adn is a bit smelly at idle. Fuel consumption is up.

It looks like the cause is under the manifold where there is (what appears to be) a spring-loaded 1" pipe that connects the sump to the intake manifold. It is leaking oil at the bottom, running along the sump gasket and either swelling up from the connection to the sump or dribbling down the pipe- which is more likely. The car loses a good amount of oil to this, even at idle there is a slight stream happening . I am able to reach down and twist the pipe around with my fingers, so it is not tight...

I figure if the pipe is leaking oil, it's sucking air so is the cause of the leak. Has anyone seen this before?

- Is it simply a broken O-ring or something else)?
- Is this common?
- Have I got to remove the whole intake to change it?

But none of this explains the engine conking out (#1)..

Has anyone heard of this before?

Any light you might be able to shed on these issues would be tremendously appreciated! Nick

[bmwrp8]

Hey all,

We have an M20 (in an E30) here which has two problems that kinda have me googling tonight. Can anyone out there help out?
This is what's wrong:

1. The engine conks out once the coolant reaches temperature, if you have the AC on. Without AC it runs happily forever.

If you start the car and turn the AC on, it runs fine at the normal 800rpm (stable & smooth but not perfect). Then, once it is just under half way on the temp gauge (6 minutes odd), it just stops dead.

All the fans and cooling system components have been changed or tested operational. New coolant, new timing belt, thermostat, MAF conversion.

Once it does conks out, it won't re-start unless you wait a long time. The starter relay clicks, (but not the solenoid), you can hear the ignition/HVAC components running, the warning and dash lights all come up fine.

- Could this be a return valve problem like can hapen on e34s? I was thinking it to be electrical. The only abnormailty is that the service indicator LEDs flash when you (try) to engage the starter motor. However it only happens when the AC is on.

The car does re-start again, when given time to rest.

2. There is definately an intake leak (though all pipes have been replaced.

If you remove the oil cap, the idle does not change. I suspect the Motronic has gotten used to running on a little 'extra ventilation'. The car misses slightly when driving off idle adn is a bit smelly at idle. Fuel consumption is up.

It looks like the cause is under the manifold where there is (what appears to be) a spring-loaded 1" pipe that connects the sump to the intake manifold. It is leaking oil at the bottom, running along the sump gasket and either swelling up from the connection to the sump or dribbling down the pipe- which is more likely. The car loses a good amount of oil to this, even at idle there is a slight stream happening . I am able to reach down and twist the pipe around with my fingers, so it is not tight...

I figure if the pipe is leaking oil, it's sucking air so is the cause of the leak. Has anyone seen this before?

- Is it simply a broken O-ring or something else)?
- Is this common?
- Have I got to remove the whole intake to change it?

But none of this explains the engine conking out (#1)..

Has anyone heard of this before?

Any light you might be able to shed on these issues would be tremendously appreciated! Nick

Tried looking at the crank position sensor?or the coil?just a guess

[Ferret]

Swap out the temperature sensors as they're only cheap...

I suspect that your air sensor is on the blink/the vaccuum leak is causing this.

My reasoning: if it's leaking and running in a default program, it'll *just* be running, as in very lean. When you switch on the aircon, the ECU tries to raise the idle a little by dumping a load more air into the manifold - and it expects the ECU to catch up and dump more fuel in. However - you've got a leak/faulty sensor and it's not running in closed loop control mode, doesnt realise there's extra air there so the engine just leans out and stalls with the extra air.

Why doesnt it do this while the engines cold? Because it's running in warm up mode and doesnt give a crap about the air flow sensor, it's running on defualt pre-programmed mixes of air and fuel.

Find your leak and the staling problem will probably vanish. Unplug the air flow sensor and see if it stops as well while warm as the engine will default to pre-programmed mode.

[genphreak]

Swap out the temperature sensors as they're only cheap... Find your leak and the staling problem will probably vanish. Unplug the air flow sensor and see if it stops as well while warm as the engine will default to pre-programmed mode.

That is a great suggestion. However, surely it would start again if this were the case... at present, once the engine stalls, the starter refuses to engage. The solenoid is not operating, so I don't think it can be that.

If it were not for this minor detail, that would be a truly brilliant piece of problem solving! Nick

... thanks for the thought though, it was a really good one!

Just found have a fix for the oil & air intake leak though:
See below for pictures and explanations...


Parts

Top of pipe requires
intake gasket, (these numbers are for m20b25)

02 GASKET ASBESTOS FREE x1 11611726012 $4.85
O-RING x1 11151714390 $1.25

Bottom of pipe requires
09 O-RING x1 11151714390 $1.25
10 FLAT WASHER x2 11151280937 $0.57

and a new spring?
12 COMPRESSION SPRING x1 11151265346 $1.61

See here;
http://e30tech.com/forum/viewtopic.p...592dd8c237f8a0

and

http://e30tech.com/forum/viewtopic.p...4724381fe0e05b

[genphreak]

Tried looking at the crank position sensor?or the coil?just a guess

Hmm. I'll check it. Good thought. I actually broke it but did a great jib re-fixing it. I tested it afterwards and all was OK. Should do so again, its been some time since that fix was done, however it should start again after stalling if this were th root cause. Thanks for taking the time to suggest it though, and reminding me to check the damned thing... Nick

[Ferret]

That is a great suggestion. However, surely it would start again if this were the case... at present, once the engine stalls, the starter refuses to engage. The solenoid is not operating, so I don't think it can be that.

If it were not for this minor detail, that would be a truly brilliant piece of problem solving! Nick

... thanks for the thought though, it was a really good one!

I have a suspicion that the starter issue is not related and it's just the solenoid on its way out...

EDIT: Watch your battery voltage as you kick in the AC...

Also : Remember that the AC relay and the Starter relay are in the same aux box... coincidence?

[genphreak]

I have a suspicion that the starter issue is not related and it's just the solenoid on its way out...

EDIT: Watch your battery voltage as you kick in the AC...

Also : Remember that the AC relay and the Starter relay are in the same aux box... coincidence?

Great... those are salient points.

The month of rain we've been having may not be helping either. I'll swap the good battery in and see what happens once the car has a known good voltage. I'll report back in the next few days. Nick

[Ferret]

Great... those are salient points.

The month of rain we've been having may not be helping either. I'll swap the good battery in and see what happens once the car has a known good voltage. I'll report back in the next few days. Nick

:P

Run it without the aircon for a bit, stall it intentionally if it's a manual box and try restarting and see if the start problem's still there without the aircon getting in the way.

[rob101]

Great... those are salient points.

The month of rain we've been having may not be helping either. I'll swap the good battery in and see what happens once the car has a known good voltage. I'll report back in the next few days. Nick

hey that hot start problem can be a heatsoak issue with the relays its very common for older bimmers. and i've heard a similar story to what you described being because of that.