Stalling

[feunfer]

I need the help of the more experienced members of this forum.

I've recently had a stalling problem with my 1988 535is with 153K miles.

It can be at a red light, when I'm starting out from a stop, when I'm backing from a stop... sometimes the car doesn't stall, but the rpm's will drop to zero and then come back to idle.

I've even had the car stall while driving in traffic. Luckily, most of the time a turn of the key and she's running again. I did, however have one incident recently where the car stalled and would not start... until I smacked the AFM.

I've done the following:

Recent tune up, including a new ignition coil
New fuel and main relays
previous owner replaced both fuel pumps about 20K miles ago and the fuel pressure regulator.
new AFM, after the no-start incident
flywheel sensors appear to be OK

The car drives well, but it still stalls, or drops off idle and returns.

Any other parts I can throw at this car? Any other ideas?

Appreciate any comments.

Thanks,

[bavarianautowrks]

CTS. Under $20, you're going to want to replace it anyway.

[Kyle in NO]

Randomly, or as the revs come down after lifting off the throttle?

[shoff535]

what is CTS ?
thanks,

[dcollin]

Coolant temp sensor

[bavarianautowrks]

Coolant temperature sensor. It's located on the thermostat housing along with a few other sensors. The CTS on your engine should have a blue connector I believe, which superceded the white ones. The sensor directly relates to air/fuel mixture and can stall the car if it is faulty.

[Xenocide]

The CTS is one of the few parts that's worth replacing without in depth diagnostics. I'm not sure it's the root of your issue (sounds more like an electrical issue than a failed sensor), but at the $20 price point and the common failure rate, I'd say it's worth throwing a new one in there.

[Mike W.]

Make sure the TPS is correctly adjusted if it's not and doesn't send an idle input, it will tend to stall coming down to idle. Also clean the ICV, if they get dirty they can be slow to react and cause stalling.

[sutton]

Not a post hijack, but related question (maybe):

Sometimes I get rough idle and holes in the acceleration, which are accompanied by a rapidly fluctuating temperature gauge needle. CTS a possibility?

[Mike W.]

Not a post hijack, but related question (maybe):

Sometimes I get rough idle and holes in the acceleration, which are accompanied by a rapidly fluctuating temperature gauge needle. CTS a possibility?

Either a bad ground or low on coolant. CTS runs the FI, not the gauge, it's a different sending unit.

[feunfer]

Thanks for all the advice. I will replace the CTS.

This is a random problem. The car will sometimes stall as soon as I start, sometimes at a stop, sometimes the rpm's will drop and then return to normal (about 700 rpm).

Concerning the TPS, the wording in Bentley is a bit confusing to me... seems my model year with manual transmission is not discussed. Does my car have a TPS?

Sorry... what is ICV...

Again, thanks for the assistance. I'll let you all know when resolved. Love the look and drive of this car, but this issue needs to go!

[Mike W.]

Thanks for all the advice. I will replace the CTS.

This is a random problem. The car will sometimes stall as soon as I start, sometimes at a stop, sometimes the RPM will drop and then return to normal (about 700 rpm).

Concerning the TPS, the wording in Bentley is a bit confusing to me... seems my model year with manual transmission is not discussed. Does my car have a TPS?

Yes it does. Mounted on the side of the throttle body.

Sorry... what is ICV...

Idle Control Valve.

[shocka]

The TPS throttle position sensor is on the side of the throttle body should have a electrical plug going into it.

[DJM1986-5]

As Mike W said, TPS is probably bad...stalling coming off idle, or needs a C hair of an adjustment, and the ICV needs a cleaning. Usually they stick open causing a high idle...

[feunfer]

Thanks again to all. Seems I have some parts to order and some work to do. I'll let you know how it all turns out when finished.

[Xenocide]

I'd test the TPS before placing any orders. While it's true that it's never a bad thing to have spare parts on hand, the TPS doesn't go bad often and is very easy to test. The first test I'd do is to unplug the TPS and see if the idle changes. If it doesn't, it likely needs to be adjusted or (much less likely)replaced. With the TPS unplugged the car assumes mid-throttle, meaning it'll still run and drive reasonably normally but idle and WOT performance will suffer. If it runs differently with it unplugged you'll know it's functioning.

A more conclusive test could be done with a continuity tester (a multimeter or even a test light). Look up the test procedure via search on this site or in the Bentley manual.

[briansmith]

While the CTS is inexpensive, I've never had one that tested good according to the simple temp. vs. resistance chart that wasn't actually fine. The TPS is an easy next stop deeper into the engine bay once you've got the multimeter out, renewed its batteries to measure resistance, taken off your zippered clothes to lean over the car, etc....
I'm curious about what made you think to smack the afm. Unless it's an electric motor that won't spin despite having good applied voltage, I don't think to smack something that I don't know isn't working.
If you don't have a way to check fuel pressure, a new fuel filter and an ear check to verify both fuel pumps working might not be a bad idea.

[feunfer]

I unplugged the TPS while the car was running... idle changed slightly, but when I plugged it back in nothing seemed to change. I did this several times, had my son listen with me. He felt the same... slight change when unplugged, no change when plugged back in. Still need to do the resistance check which means I need to get the multimeter ready.

I tapped - didn't hit it very hard - the AFM because I called a friend and he thought the flap might be hung up. It really doesn't mean anything as it may have started anyway, having sat for awhile. If I had someone with me that could have tried to start the car while I tapped on the AFM - that would have provided better confirmation, but since I tapped on the AFM, then started the car it may or may not have been the AFM.

Fuel filter was replaced in June; previous owner replaced both fuel pumps about 20K miles ago.

Again... thanks to all for your comments. Love this car... just need to resolve this issue.

[feunfer]

Today I pulled the ICV (I assume that's what is called the idle air stabilizer valve in Bentley and part #3 on real oem AFM pictorial).

When I shook it, there was movement, but it looked pretty dirty so I cleaned it with carb cleaner. I reinstalled, and with the ignition on I could hear a 'click' sound.

Before I installed after cleaning, I could shake the ICV and hear movement... but it doesn't move much. Not having experience with this, I don't know if that's OK or not. Is it?

Anyway, I started the car, but it's still stalling.

Summary, so far I've:

Cleaned/checked the ICV as above;
Replaced the AFM;
Unplugged the TPS while running and notice a small change
Complete tune up in June
New fuel and main relays
Previous owner replaced both fuel pumps - 20 K ago

I'll keep trying, but getting to the point that I may just start buying new parts.

Still open to suggestions...

[Mike W.]

After cleaning with spray carb cleaner the ICV should move easily with the flick of the wrist. Move it with a small screwdriver too, to test travel, it should go from full open to full shut. Some caution not to lube it but I don't know why. Use a light lube if necessary, not WD40 or a penetrant. The TPS doesn't really affect idle, it does serve to limit idle speed to ~1500 or so where it cuts off fuel and tells the ECU when an idle condition is going to be present so it can react sooner than just by idle speed alone, ie coming up to a stop sign and letting off the gas. If your ears are decent you might be able to hear it click testing it with the engine off, I used to be able to. But a meter is a much better test, although I haven't seen the idle switch fail, unlike the WOT but that's not the current issue. I really don't think new part will be needed with either the ICV or the TPS.

[feunfer]

When I cleaned the ICV, I tilted it back and forth and could hear the movement, but it doesn't move very far. I assume that's normal, otherwise this could be the problem.

Previous owner recently told me he replaced the TPS, so that's probably not the problem.

Meanwhile, the idle issues continue, but are strangely intermittent. Yesterday morning when I drove to work I had several stalls and stumbles in rpm. On the way home, very little problem. Today, on the way to work, the car either stalled or stumbled 5 -6 times. One the way home, nary a problem... one minor stumble in rpm. To the gym later and no problem.

Maybe she's not an early riser! Or maybe its the alignment of the sun and moon in the fourth quarter, etc..

Checked vacuum hoses last night, though I'd replaced some of those already. May be something to do there, but those I thought were bad did not affect idle when I disconnected while the car was running.

I'll keep at it until the car is 'normal' again.

Again, thanks for Mike W and thanks to all that have taken the time to help me out.

One other question - off subject. Will the original DIN radio from an e30 fit in the e28?

Again, thanks...

[Mike W.]

Just because the TPS is good doesn't mean it's adjusted properly, test it with a meter. If the ICV doesn't move freely that would be a problem, it needs to react quickly to prevent stalling. And while wide open on the ICV isn't all that far open just due to the shape of it, it should move to wide open. It can be hard to tell if you're just flicking it by hand though.

[feunfer]

After having cleaned the ICV, reinstalled and then have the problem return... I just replaced the ICV and it appears that was the issue. Two days without a stall. Maybe I shouldn't speak so soon, but I'm hopeful this is it.

Then... the fun never stops.

My clutch starting squeaking recently. Annoying squeak when depressed, then a different sound on release. I removed the lower panel and used silicon spray to try to stop the noise. It worked for a short time, but the noise has come back... and now I'm having intermittent trouble shifting. At times I can't shift easily to reverse or first. Sometimes releasing the pedal and clutching again solves the problem. But the clutch is suddenly strange. Seems I have to depress it further than usual and is engaging lower than before.

I searched the forum and read about the over center helper spring and also that the first sign of pedal box cracks are engagement right off the floor which is happening, but my pedal doesn't go easily to the floor.

Check the clutch pedal adjustment to what's in Bentley. Bentley says firewall to clutch pedal face should be 10 + 1/3-1/8 inches. I measured 5 3/4 inches to 6 inches. Of course the carpet must affect this measure, but it doesn't seem that Bentley is correct as the pedal was never 10 inches from firewall to pedal face.

I should mention that when I bought the car it included a e28 M5 clutch kit which was installed less than a year ago. Prior to the install, the clutch was very difficult to operate and I was told to change the clutch soon so I didn't damage the pedal box. When the M5 clutch was installed, my shop said the pedal box was in good shape.

So I'm at a loss with this. Could it be the slave cylinder? Or maybe the over center helper spring??

I have little time to work on this... perhaps Friday. Should I stop driving the car until then??

I continue searching the site, but any advice is appreciated.

[feunfer]

Well, after solving the stall problem by replacing the ICV, and the clutch problem by replacing the bracket that was cracked all the way through... this is the fun day I had today!

I drove all over town today trying to finish some Christmas shopping (Miami... too much fun) then about 3 miles from home I pull into the circular ramp to a local mall's parking area (my last stop... literally!).

The ramp first dips down, then climbs to the parking level (deck 4). I start down, then as I begin the ascent the car dies!! Sputters, lights on the dash, then it just quits. Will not start after several attempts... after running perfectly all day! Everyone is honking their horns as I'm blocking the only parking entrance.

Two young guys help me push it back up the ramp and out... They ask if I want to park in their spot, but I try to start the car and now it seems fine.

Off I go - a whopping 100 feet or so and it stops again... same scenario. This time it's not starting and now I'm blocking the exit lane from the garage. People are not pleased. After I call the towing company, I push the car back and out of the way... and wait.

I wait an hour for the tow, but the young man is very professional and does a good job getting the car on the sled (without damage to the air dam).

After I'm home about a half hour I decide to see if I can figure out what's going on. I open the hood (again), futz with some connectors, none of which seem to be loose or a problem, then start the car. It starts right up!!... idles smoothly (for an e28!), and I let it run about 20 minutes without a problem. I back up in the drive, move forward several times (at this point I do not want to try to drive and get stuck again). I throttle the car almost to red line several times, let it settle down and, as I've said, let it idle for a long time. No problem.

The only thing I did in the morning is add a small amount of oil... but the dip stick was replaced correctly. I checked that when I first had the problem.

Like a friend of mine said, this car will give me something to do...

Any ideas??

[Tammer in Philly]

Last one sounds like an intermittent bad fuel pump relay or a shady connection on the fuse. Replace that relay and fuse and make sure you adjust the tabs on the fuse for good contact to the new fuse.

A rapid die without a sputter is usually electrical in nature.

-tammer

[TheLazyDog]

what is CTS ?

Sorry... what is ICV...

what is BMW acronyms

[feunfer]

Thanks Tammer,

I will check this but maybe didn't communicate the issue very well. When the car 'stalled' it didn't just shut down. There was some sputtering and lights flashing and it did not respond to the throttle. It cranked when I tried to start again, but nothing.
We'll see what I find.

Steve

[Tammer in Philly]

Thanks Tammer,

I will check this but maybe didn't communicate the issue very well. When the car 'stalled' it didn't just shut down. There was some sputtering and lights flashing and it did not respond to the throttle. It cranked when I tried to start again, but nothing.
We'll see what I find.

Steve

I still think that sounds like a fuel pump fuse/relay. Lose fuel pressure, engine stutters, alternator/dash lights come on, it dies. Doesn't respond to throttle because there's no juice to the fuel pump. When you try to start it, it cranks but can't fire with no fuel.

-tammer

[mpowertech]

Had some similar symptoms and traced the problem to one of the terminal connections on the coil. Make sure bracket nut (10mm) is tight too, as it can cause vibration leading to this condition. Dist. cap and rotor condition. Moisture? Plug wires and spark. Its possible that this is a spark issue. Also check battery connections and grounding straps. There is one fwd inboard of the fuse/relay box in the engine bay. You sound determined, let us know how you succeeded in fixing it!

[feunfer]

It was the pre-delivery fuel pump. All better now... hopefully for a long time. Thanks again to all of you that have helped me to learn about this great car.