1989 e30 Convertible stall when warm issue, rough idle

[Winhotel]

BMW e30 1989 Convertible Automatic

I've been searching all over the internet and I'm just running around in circles. Let me first tell you what was done to the car. I've pretty much rebuilt this whole thing.

1. Head / exhaust / intake gasket replacement / cam seal / crank seal / Timing belt / Water Pump / Head job / Valve Adjustment
2. Spark plugs & wires
3. Distributor cap & rotor
4. Idle Control Valve
5. Crank Position Sensor, Coolant Temp Sensor, O2 Sensor
6. Main Relay, Fuel Pump Reply
7. Throttle position sensor, on the dot with ohm and correct calibration reading

When the problem occurs:
1. The car starts when cold, but after driving when I come to a stop light, it will stall.
However, to prevent it from not stalling I have to hold the brakes and rev the car to about 1000 RPM. If I were to let go during a stop it will die.

2. If I start the car up and leave it alone after about 5-10 minutes it will start to idle funny. The RPM will dip, and the engine will compensate to bring to about 750-1000, it will continue to dip and compensate, and finally it will eventually just die.

Things I've tried:
1. I've tried disconnecting the MAF, when I do the car immediately dies
2. Smoke test, no leaks
3. Tried swapping and changing fuel pump relay and main reply with no success

Could this be:
1. Fuel pump
2. Fuel filter
3. Fuel pressure regulator
4. Alternator not supplying enough volts?, but battery is good though, shouldn't be alternator.

9/11/17 Update

1. Changed fuel regulator
2. Changed fuel filter
3. Test fuel pump, cleaned strainer
4. Test MAF
5. Changed and swapped ICV, test resistance on ICV *GOOD* (3 plug)

None of these helped.

However, I took the fuel pump cover to listen if the fuel pump would fail at any time before the car would stall. And noticed it did not. It would just shut off at the same time the car would shut off.
I don't think it's a fuel delivery issue and maybe a voltage issue.

I did stick a voltage test on my battery and noticed when the car would idle good the battery was at 13.75 V, it would start to change and fall to 12.65V when the car would die, it would accelerate on it's own and it would lose power on it's own at park, eventually dying. While its trying to compensate for the power loss, the battery voltage is fluctuating, this is a new BOSCH battery.

I notice the OBC computer display light is flickering, but all other lights are good.

Every once in a while the 1215 code would pop up, but then after revving it would disappears and eventually come on intermittently, voltage issue?

Could this be a problem with the alternator?

I'm not sure what is going on and I want to make sure before I drop some more cash on this.
What would make the car no idle properly when its warm?

[vertbmw]

Had a similar issue with mine, turned out the ground cable between oil pan and frame rail was corroded and frayed causing too much resistance and a poor ground. I verified this by using a jumper cable from the engine to the frame of the car and had no issues with it hooked up. When I removed cable the symptoms returned.

[Winhotel]

Had a similar issue with mine, turned out the ground cable between oil pan and frame rail was corroded and frayed causing too much resistance and a poor ground. I verified this by using a jumper cable from the engine to the frame of the car and had no issues with it hooked up. When I removed cable the symptoms returned.

I noticed the sleeve isn't on the ground cable anymore. I took it out and put electrical tape all around it, still getting the same problem. I'm going to try and order a new ground cable.

[superj]

add an extra cable or two to ground things. I always do on e30s and jeeps. seems to smooth stuff out.

[Winhotel]

With a multimeter, if I put a negative terminal on the negative battery, and I use the positive on any part of the chassis am I suppose to get 0.00 Ohms? or something, cause I'm getting 1 still, but all around the throttle body, alternator, etc I'm getting 0.00-0.001. No reading on the chassis all around

Also, K6 relay. When I click the relay together, I hear something blowing, but the fan isn't spinning. Is it suppose to do that? However the fan does run, when I turn on the car.

[Winhotel]

9/15/17 update

1. Alternator checked good
2. Battery recharged and rechecked. I'm getting about almost 14V when car is running. Battery is good.

Getting some white smoke gas smell, bad idle, if I let go of the gas pedal car shuts off, code 1222 pops up.

Getting black sparks plugs all 6, pulled out O2 sensor, O2 sensor is black too. Looks like it can easily rub off.


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[Winhotel]

I'm really thirsty to get this thing fixed. I forgot seafoam was added to the gas tank.

1. Emptied the tank and added new fuel, smoke went away, no more gas smell coming from the gas. Cleaned spark plug and O2 sensor. Code that appears is 1222.

Car still does not idle, I have to hold down the pedal, if I let go it will die.

What could it be?

[Elvir]

I had similar problem and problem was in EVAP valve. Petrol vapors flooded intake. I put accurate EVAP valve from E36 and now idle is fine.

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[Winhotel]

So, I did a leak down test. Multiple times because I really wanted to make sure my reading were right.

I used a balloon to know the air was coming up to figure out where TDC and compression was for each cylinder. I pumped 20 PSI and stuck in it 100% leak. I stuck in 80 PSI about 90% leak on all cylinders.

1. Throttle body open - no noise
2. Exhaust at the rear of car - no noise
3. I have no bubbles in the radiator, as I had recently changed the head gasket. The car was working for about 100 miles before all this even happened.
4. Dip stick - VERY OBVIOUS hissing sound

I just want to make sure that on these M20B25 engines there as anything special I had to do for this test. If not, yes I am having 90% - 100% on these cylinder, all sounds coming from the oil dip stick.
The park plugs are charcoal black, and so is the O2 sensor, but they can easily be wiped off, so it's no like crazy carbon built up.

Is this it? Is this the answer? my rings are screwed?! The car does have 265,000 miles on it, and engine block has never had anything done to it.

What else should I look out for? Any other tests to make sure its the rings before I pull out the engine and rebuild?

[aaverhulst]

How about a compression check on each cylinder? Then put oil in each plug hole and run test again.

[DBShiznit]

May be a long shot but could be the issue. I had a really rough idle with my 325i. Turned out to be the vent tube that goes from the bottom of the intake to the top of the engine block. Mine was actually not in place from when someone did the head gasket on the car. I twisted the tub and it slide right into place and the rough idle is gone. I still have a slight misfire but that's something else to chase. Hopefully this helps. It look like you've done most of everything that would be related to your issue. Let me know if this helps.


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[superj]

your oil filler cap seals properly? if you have any vacuum leak that's of decent size, the idle will not hold

[Winhotel]

yea guys, I've been diagnosing this thing for like almost 2 weeks. Almost everything has been replaced.

Oil filler cap is good. I checked the EVAC valve.

Here's what I'm getting for dry compression test. All spark plugs out, fuel relay out. throttle all the way down
Cylinder 1: 150
Cylinder 2: 150
Cylinder 3: 150
Cylinder 4: 165
Cylinder 5: 155
Cylinder 6: 100

They didn't seem to pop up immediately to the max point, it takes about 3 revolution until they reach those numbers

I did a wet test on Cylinder 6 and it went to 105

Also note that leak down test at 80-100 PSI shows extreme leak, 90%-100% on all cylinders. Intake valve no hiss, exhaust pipe no hiss, radiator cap no bubbles or noise, hiss can be heard from oil dip stick when open, and also can be heard when oil fill cap is open straight from the top of the head, but that might be the hiss that is going down into the oil pan and coming out of the dip stick. Unless it's leaking somewhere else?

Is this sounding like a piston ring problem? All the pistons? oh man. I just want to make sure before we pull out the whole engine. Planning on doing it this Sunday and making a youtube video.

[aaverhulst]

#6 definitely has a problem. They say you need to turn over 3-5 times to get results. If bad rings I think # 6 would have gone up more for the wet test. How much oil did you put in? I'd recheck the valves on #6. Generally if the cylinders are within 10%, that's OK. Yours are except for 6.

[95BMWIC]

A wet test (with oil) should bring up the compression with bad rings (more than just 5psi) - It sounds like you have a valve not sealing - especially since the wet test didn't change anything. You might not hear a hiss.

With those numbers - pull head and inspect. Examine piston heads and cross hatch in the cylinder walls. Look for nicks, gouges, etc to determine if you need bottom end work. A valve job and cylinder head resurfacing does not cost a lot, but bottom end can be more expensive...

[Winhotel]

Any reason why the leak test would show 90%-100% on all cylinders?

[95BMWIC]

When you changed your head gasket - did you have the head resurfaced? Did you inspect the cylinders? Did you inspect your fuel injectors? (I didn't see that you listed that) Any plugs fouled?

One cylinder at 100psi (others at 150) is an indication something is wrong - however, I don't think that would cause the engine not to idle.. (It would if the leak down test indicated a stuck valve on cylinder 6 only). a little compression loss on one cylinder would show up on performance, acceleration, power.

Also - if your compression test yields 150 + compression on 5 of the 6 cylinders and the leak-down test indicates a 90 -100% loss on all cylinders - I would suspect the leak down test procedure/measurement is faulty. Those 2 measurements contradict too much - how can you generate compression when there is a 100% loss of pressure?

A leak down test is measured in loss - 90-100% indicates a major malfunction (valves are open when they should be closed). If the car was running after the head gasket fix - then the leak down test itself was done incorrectly. Your loss should be somewhere between 5-10% maybe a bit more if a bit worn.

There is an o-ring on the oil dipstick tube and dipstick that can be replaced fairly easily. Vacuum leaks can cause poor idle if large enough.

[aaverhulst]

Any reason why the leak test would show 90%-100% on all cylinders?

I have never done a "leak down" test so.... but if you have 150+ psi on 1 - 5 cylinders, I'd say the test was worthless. Maybe the it was not run correctly.

Back to your wet test, did you put enough oil in the spark plug hole? Because if it only went up 5 psi then you may have a valve problem or head gasket leak. First I would check to make sure my valves were set correctly on #6. Too little valve clearance would cause that valve to leak or burnt valve.

[95BMWIC]

I missed that you indicated "black plugs" - carbon fouling can be fuel delivery (too rich) or not a hot enough spark (check coil) or timing issue (ECU). Just a thought - did you double check your timing marks after the head job? If you are a tooth off - it may cause these type of issues (try searching on this topic).