Need your kind expertise with my E28

[Disappear__]

Hey guys!

Posted the same on Reddit and was told to post here as well as this forum is full of experienced E28 owners.

Apologies in advance for the slow explanation, English is not my first language and my car vocabulary is not so good.

I have an issue with my E28 535is that I've imported from NY. Took it to 2 different workshops (second workshop is an expert in old BMWs and kept my car for over 2 months and still couldn't figure out where the problem is).As you can see in the video, car constantly switches off, doesn't matter if cold or warm.
Almost certain the issue is electrical but again can't be sure and ofc you guys are the experts. Tried changing crankshaft sensors, still the issue is persistent. Even changed the ECU and still the same.
The issue only happens when the RPM drops, so if I'm driving (inner roads or highway) it's good, but once I slow down for a bump or roundabout, almost immediately switches off.

Can't upload videos here so will link the Reddit thread so people can understand the issue (hope that's not against forum rules):
https://www.reddit.com/r/e28/comments/1 ... th_my_e28/

Would be forever grateful if you guys had any ideas or suggestions!

[Aldo525]

Does the car start and idle smoothly? Does the engine only stall when the RPM drop rapidly? If so, I could consider:
Incorrect TPS adjustment (or a faulty TPS), incorrect intake throttle adjustment, or a dirty or faulty ICV valve.

I'm assuming the spark plugs, wires, distributor, and rotor are new.

Those would be my initial thoughts.

However, a workshop specializing in older BMWs would have already considered these possibilities.
 

[Disappear__]

Does the car start and idle smoothly? Does the engine only stall when the RPM drop rapidly? If so, I could consider:
Incorrect TPS adjustment (or a faulty TPS), incorrect intake throttle adjustment, or a dirty or faulty ICV valve.

I'm assuming the spark plugs, wires, distributor, and rotor are new.

Those would be my initial thoughts.

However, a workshop specializing in older BMWs would have already considered these possibilities.
 

Yeah man that's exactly the issues. Everything you've listed was checked/tested and ruled out, that's why as last ditch effort I'm posting here.
Car always starts that's never an issue, but almost immediately stall while idle and when driving and RPM drops.
Considering replacing TPS and such small parts with new ones just in case, even though the mechanic said it's not the cause of the problem but I'm pretty much desperate at this point tbh.

[Aldo525]

Does the car start and idle smoothly? Does the engine only stall when the RPM drop rapidly? If so, I could consider:
Incorrect TPS adjustment (or a faulty TPS), incorrect intake throttle adjustment, or a dirty or faulty ICV valve.

I'm assuming the spark plugs, wires, distributor, and rotor are new.

Those would be my initial thoughts.

However, a workshop specializing in older BMWs would have already considered these possibilities.


 

Yeah man that's exactly the issues. Everything you've listed was checked/tested and ruled out, that's why as last ditch effort I'm posting here.
Car always starts that's never an issue, but almost immediately stall while idle and when driving and RPM drops.
Considering replacing TPS and such small parts with new ones just in case, even though the mechanic said it's not the cause of the problem but I'm pretty much desperate at this point tbh.

 

 

In my experience, even if the checks and readings of parts like the TPS and ICV are correct, those parts are still faulty. I would make sure to replace both parts with new ones. The TPS would be the first to replace; OEM Bosch parts are still available (expensive...) but there are other brands. The ICV is another issue; new OEM parts are hard to find and very expensive, but again, in my experience, OEM Bosch parts are the only ones that work well (I tried two other cheaper brands and it was a disaster).
I would also change the temperature sensor located in the thermostat housing (very cheap, it's worth it). Finally, the AFM... at least make sure it's clean and the flap moves freely. There are also tutorials for checking its operation.

If you've already tried another ECU and new position sensors, I think there's nothing else to check/replace.

Last and very obvious, vacuum leaks???

[Federico]

You could also check the voltage regulator; It's easy to remove from the back of the alternator.
It can cause the engine to die when the brushes are worn out.

[Shawn D.]

If this hasn't been done, clean the throttle body and set the throttle plate idle setting to specification.  Do this before changing the TPS and ICV.

Understanding that you're not experienced with English, instead of saying "switch off," say "quit running."  "Switch off" implies a circuit is being switched by a sensor or the ECU, and could lead to false diagnosis.

[turbodan]

A compression test might be worthwhile. This may be a matter of low compression or high cylinder leakage.

[Disappear__]

Yeah man that's exactly the issues. Everything you've listed was checked/tested and ruled out, that's why as last ditch effort I'm posting here.
Car always starts that's never an issue, but almost immediately stall while idle and when driving and RPM drops.
Considering replacing TPS and such small parts with new ones just in case, even though the mechanic said it's not the cause of the problem but I'm pretty much desperate at this point tbh.

 

 

In my experience, even if the checks and readings of parts like the TPS and ICV are correct, those parts are still faulty. I would make sure to replace both parts with new ones. The TPS would be the first to replace; OEM Bosch parts are still available (expensive...) but there are other brands. The ICV is another issue; new OEM parts are hard to find and very expensive, but again, in my experience, OEM Bosch parts are the only ones that work well (I tried two other cheaper brands and it was a disaster).
I would also change the temperature sensor located in the thermostat housing (very cheap, it's worth it). Finally, the AFM... at least make sure it's clean and the flap moves freely. There are also tutorials for checking its operation.

If you've already tried another ECU and new position sensors, I think there's nothing else to check/replace.

Last and very obvious, vacuum leaks???

Thank you so much for your detailed reply. I'm not the best when it comes to mechanics so forgive me if this is a silly question, but I was checking the TPS earlier and got confused cause it looked so different than any video/picture I found online. It looked like a metal plate with 3 cables with a round connector, opposite to the 3 pin flat harness that I'm finding online.
Same goes with the temp sensor, it had 2 small hose like connectors rather that the 2 pins connector (unless I was inspecting another sensor).
Can post pictures if my description is confusing.

[Disappear__]

You could also check the voltage regulator; It's easy to remove from the back of the alternator.
It can cause the engine to die when the brushes are worn out.

Thanks for your reply. Did some research on voltage regulator and might end up installing a new one, might not be causing this issue but I now understand that it can be the cause of battery drain which I also have in my car, so two birds one stone kind of thing.

[Disappear__]

If this hasn't been done, clean the throttle body and set the throttle plate idle setting to specification.  Do this before changing the TPS and ICV.

Understanding that you're not experienced with English, instead of saying "switch off," say "quit running."  "Switch off" implies a circuit is being switched by a sensor or the ECU, and could lead to false diagnosis.

Appreciate the reply brother and thanks for the info!

[Disappear__]

A compression test might be worthwhile. This may be a matter of low compression or high cylinder leakage.

Thank you so much, will look more into that as well.

[Aldo525]

Thank you so much for your detailed reply. I'm not the best when it comes to mechanics so forgive me if this is a silly question, but I was checking the TPS earlier and got confused cause it looked so different than any video/picture I found online. It looked like a metal plate with 3 cables with a round connector, opposite to the 3 pin flat harness that I'm finding online.
Same goes with the temp sensor, it had 2 small hose like connectors rather that the 2 pins connector (unless I was inspecting another sensor).
Can post pictures if my description is confusing.

 

 

What year is your car??....Uploading photos to the post involves (what I do) first uploading the photo to a program like Imgur, and then using the link (Direct Link) to that photo on Imgur and attaching it here using the "mountain photo" icon (it says "Image"—is there a better description??? ...) at the top when you reply to the post. That way, the photo will be attached to your reply.

Now, I don't think you're looking at the TPS. What you're describing sounds familiar to a system in older 533i models, but not in a 535is. And the temperature sensor isn't the one with the two hoses; that's a switch #4 in the picture below. Temp sensor is #7, normally white or blue head (no brown)



And the TPS should be #21

[Disappear__]

Thank you so much for your detailed reply. I'm not the best when it comes to mechanics so forgive me if this is a silly question, but I was checking the TPS earlier and got confused cause it looked so different than any video/picture I found online. It looked like a metal plate with 3 cables with a round connector, opposite to the 3 pin flat harness that I'm finding online.
Same goes with the temp sensor, it had 2 small hose like connectors rather that the 2 pins connector (unless I was inspecting another sensor).
Can post pictures if my description is confusing.

 

 

What year is your car??....Uploading photos to the post involves (what I do) first uploading the photo to a program like Imgur, and then using the link (Direct Link) to that photo on Imgur and attaching it here using the "mountain photo" icon (it says "Image"—is there a better description??? ...) at the top when you reply to the post. That way, the photo will be attached to your reply.

Now, I don't think you're looking at the TPS. What you're describing sounds familiar to a system in older 533i models, but not in a 535is. And the temperature sensor isn't the one with the two hoses; that's a switch #4 in the picture below. Temp sensor is #7, normally white or blue head (no brown)



And the TPS should be #21

Thank you for the very very detailed explanation on how to upload images

https://imgur.com/a/TTeSEbd

Grouped all images in one link above.

My car is an 87. Watched 2 different videos on changing TPS and coolant sensor so going by the location of the sensors in those videos. Unless different specs/model years matter in this? not sure, was just confused when inspecting those 2 parts in my car.
The green sensor is the one I mentioned but seems different than the ones in the videos even those its the same location? And the TPS looks completely different as is the connector, that's why was confused after inspecting the 2 parts.

[Aldo525]

Thank you for the very very detailed explanation on how to upload images

https://imgur.com/a/TTeSEbd

Grouped all images in one link above.

My car is an 87. Watched 2 different videos on changing TPS and coolant sensor so going by the location of the sensors in those videos. Unless different specs/model years matter in this? not sure, was just confused when inspecting those 2 parts in my car.
The green sensor is the one I mentioned but seems different than the ones in the videos even those its the same location? And the TPS looks completely different as is the connector, that's why was confused after inspecting the 2 parts.


 

 

 

 

 

OK....now I see your pictures and your TPS. See this thread:

viewtopic.php?t=137817

My mistake, I had seen that type of TPS on the forum but I thought it was used in older models like the 533i, and no, it was used in later models with automatic transmission like the 535i (at least that's my understanding).

Re the "sensors":Green one it's a switch that opens or closes the vacuum in the hoses when the coolant reaches a certain temperature. I don't think a faulty switch would cause the engine to stall. I don't have that switch on any of my engines, so I can't say how critical it is if it's bad. I would at least try bypassing it by connecting both ends of the hoses and seeing what happens.



And here are the others:

Blue arrow: Coolant temp sensor (blue head). Critical for motronic management. I suggest to buy a new one. Cheap.
Red arrow: Thermo-time switch (brown head). Used only on cold start to give more fuel through the CSV. If bad, the CSV don't work so no extra fuel during cold starts or CSV always open resulting in rough idle.
Yellow arrow: Temp sensor for temp gauge in the instruments cluster. Not related with the engine stall issue.

[Disappear__]

Thank you for the very very detailed explanation on how to upload images

https://imgur.com/a/TTeSEbd

Grouped all images in one link above.

My car is an 87. Watched 2 different videos on changing TPS and coolant sensor so going by the location of the sensors in those videos. Unless different specs/model years matter in this? not sure, was just confused when inspecting those 2 parts in my car.
The green sensor is the one I mentioned but seems different than the ones in the videos even those its the same location? And the TPS looks completely different as is the connector, that's why was confused after inspecting the 2 parts.


 

 

 

 

 

OK....now I see your pictures and your TPS. See this thread:

viewtopic.php?t=137817

My mistake, I had seen that type of TPS on the forum but I thought it was used in older models like the 533i, and no, it was used in later models with automatic transmission like the 535i (at least that's my understanding).

Re the "sensors":Green one it's a switch that opens or closes the vacuum in the hoses when the coolant reaches a certain temperature. I don't think a faulty switch would cause the engine to stall. I don't have that switch on any of my engines, so I can't say how critical it is if it's bad. I would at least try bypassing it by connecting both ends of the hoses and seeing what happens.



And here are the others:

Blue arrow: Coolant temp sensor (blue head). Critical for motronic management. I suggest to buy a new one. Cheap.
Red arrow: Thermo-time switch (brown head). Used only on cold start to give more fuel through the CSV. If bad, the CSV don't work so no extra fuel during cold starts or CSV always open resulting in rough idle.
Yellow arrow: Temp sensor for temp gauge in the instruments cluster. Not related with the engine stall issue.

Ah okay now the TPS part makes sense. Issue now is that this TPS seems like a pain to find, even with the part number so that will be tricky.
Thanks for linking the other thread, that dude seems to have the same engine as mine. Even the pictures you've posted, was very confused watching different videos online so seems like this is how the automatic 87/88 535i came as.

[Profile36]

Your issue could very likely be related to fuel. In your trunk, remove the in-tank fuel pump and inspect the fuel tank with a flash light for rust. There is a good chance you have a build up of rust clogging your fuel lines/pump for proper fuel delivery.

A more accurate way of doing this test would be to put a fuel pressure gauge in line under the hood. Then simply, start the car, blip the throttle open and see if you have a problem with pressure while the engine dies. 

-M

[concordealex]

I would look closely at the fuse panel. I had a problem similar to you where the car would shut off without warning. I tried everything—resoldering the ECU, replacing the fuel pumps, new crank position sensors, putting a new coil in, new relays, and nothing worked. The car would be fine for weeks but then shut off while driving.

I even checked every sensor with a multimeter. No problems. Finally, I noticed that fuse #1 (which powers the fuel pump) was slightly tilted. Turns out the plastic had melted around the fuse holder, making it loose and randomly cutting off the fuel pumps.

I installed the Holy Grail Labs blade fuse kit over a year ago and haven’t had any problems since. My 535 has been great since then, at least once I sort out a driveline vibration….

[arctic745]

If I read your post right, you imported the car from NY.   If so, it might have a resistor soldered inline with the motronic temp sensor (Blue).  Those were done to make the CPU think the engine was a little cooler than it was richening the mixture to help with idle and lean surge with US emissions.  I think it was a dealer fix in the day.  The resistor is usually in the rubber boot of the connector and the solder joints break. If so, it can be intermittent,  or a post startup stall - its starts on the thermo time sensor, but when it kicks over to the regular temp sensor, it gets no signal.

Might not be your issue, but its an easy check under the boot.