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-   -   525I 1991 dies sometimes at Idle (http://www.bimmerfest.com/forums/showthread.php?t=658038)

fryntyr 11-13-2012 06:32 PM

525I 1991 dies sometimes at Idle
 
Hello, I've searched the forums over several weeks while working on my issue and while symptoms have improved, the problem of dieing still happens at stops sometimes. Looking for some ideas before I get stuck paying to have it looked at.

Bought this from a friend who replaced the head due to a blown head gasket/cracked head. It recieved all new cooling system at the same time. It also received a new O2 sensor after he checked the code that kept coming up after it was all together which I would expect after having antifreeze go through the exhaust, that ruins a 02 sensor right away.

It has and still does have a 02 sensor code the keeps tripping. It had a constant surging at idle but never died when I got it. I found several vacuum leaks that I fixed which helped smooth the idle alot but still had idle issues. Then pulled the ICV and cleaned it which also helped. It still dies every once in a while but idle is fairly constant until it dies.

When it dies it almost is like a miss and cuts out. Sometimes if it doesn't die but has the miss sensation it will actually surge the Idle speed up several hundred RPMs then come back down and stay around the normal 750.

It doesn't always do this at every stop but at least a few times everytime it's driven.

The RPM really doesn't move around on the tach so it's really close to being ok. If I get figure out what is causing it to die I'll be happy.

Could the Cat be plugged and causing issues like this. Maybe the blown head gasket pushing through coolant plugged it? Could the 02 sensor be ruined quickly and be the cause if the vacuum leaks and ICV weren't fixed when replaced.

Help!!!

BMR_LVR 11-13-2012 06:53 PM

Welcome to the Fest.

That's a very nice, descriptive post. I wish more first timers (heck, even some of the old timers don't get descriptive enough :D) would post like that. Do you have the M20 or the M50? It still sounds like you may have a vacuum leak causing some unmetered air to get in the intake.

There are a lot of hoses and areas that can cause a vacuum leak. Have you tried spraying some carb cleaner on all areas? If you get a sudden increase in idle, you have found a leak.

Cleaning the ICV was certainly the correct thing to do as well. It is possible that the ICV is faulty, but I don't thiat this is too common.

You may want to delete the O2 sensor code through the stomp test, disconnecting the DME for 5 minutes or removing the battery posts and touching them together for a few minutes. Whatever is easiest for you.

After that, see if the car behaves better. If it acts up again, do the stomp test and see what codes come up. That may point you in the right direction.

Good luck and let us know how it goes. Hoped this helped a little.

robertobaggio20 11-13-2012 07:56 PM

Try cleaning out your tps, its a 5 minute job fortunately :

http://www.bimmerfest.com/forums/sho...d.php?t=658005

paperplane94 11-13-2012 08:04 PM

MAke sure the FPR is not letting too much gas into the engine.

Monsignor 11-13-2012 08:12 PM

FPR is Fuel Pressure Regulator by the way. We don't usually see that acronym thrown around, just clarifying. Don't mean to step on any toes

paperplane94 11-13-2012 08:30 PM

No worries, better to clarify.

robertobaggio20 11-13-2012 10:16 PM

Classic icv and tps. That's idle control valve and throttle position sensor.

Anyway.....longshot but in case the tps does not solve the problem.....disconnect the engine coolant temperature sensor. That can cause really weird engine symptoms too. The sensor is under the intake manifold for m50 engines and is tough to get to...do this when the car is cold. There are two sensors, only one goes to the dme (that's ecu) and the other goes to the dashboard temp gauge. You want to get the first one. Its no biggie if you get the second one as well but find some way to avoid mixing them both up if you disconnect both and you need to reconnect one.

If you disconnect the ect sensor and your problem goes away, then you've got the culprit. Drive with it off until you can get a new one fixed in. Your fuel economy will suffer somewhat in the interim period. IN fact, forgot, that's another clue that your ect is busted. Along with your current symptoms, your fuel economy should be tanking. If you're also getting repeated o2 sensor codes, (suggesting that repeated overfuelling is taking place) then you've got yet another symptom.

So please clean the tps, that's the easiest thing to do and my money's on that, and if the problem does not go away, then disconnect the ect and see.

Please update your thread with your findings later. Thank you.

rgds,
Roberto

fryntyr 11-14-2012 12:07 PM

Thanks for all the feedback, It's a M50.

To me, I think it's a bit doggy too, but then again I don't have anything really to compare it to.

I will try cleaning the TPS and play with the ECt and let you know.

I did buy a used PEAK code reader/reset and the code that does come up as the 02 and comes back even after a reset. It doesn't stay on but comes on once in a while, then goes back off. I've read here, just means the readings are haywire.

I'll look for another vaccuum leak as well.

I did notice the plastic fitting in the bottom/back of the Intak manifold, where the ICV hose connects to the intake, is not the tightest fit in the world. I can't see well enough to see how if snaps in there and believe it has some sort of O-ring to seal it. That could be a source of a vaccuum leak, maybe.

Thanks again. update soon.

fryntyr 11-14-2012 07:15 PM

Cleaned the TPS contacts and plugged it in with dielectric grease. Didn't change. Unplugged the #1 ECT and didn't really change. then it died once when I took it down the road and came to a stop.

I think I should clarify to that the idle isn't perfectly smooth but close. It has a small roughness and surge, can't read on the tach.

It does smell a bit riich to me. I would say the muffler is a bit worn out as it kinda sounds like a fart can but it doesn't leak anywhere so I assume it shouldn't really effect runnability.

I'll just keep trying stuff as I hear ideas.

Thanks again.

robertobaggio20 11-14-2012 10:23 PM

Is the #1 ect the one for the dme, or the one for the dashboard temp gauge ? You need to unplug the one for the dme.

Try this (and we're on a fishing expedition here), unplug the ect, clear all the error codes (via the stomp test or by unclamping the ecu for a few minutes), then run another test.

While we're on the fishing expedition, lets rule out the o2 sensor as well. If the above does not help, then pull the O2 sensor's relay. It should be in your dme box...please check with the bmanual for the exact location for your car. That's an easy way to deactivate the o2 sensor. Then drive the car again and see if the problem recurs.

Whatever you try, if the problem does not recur, keep it in test running mode for 2-3 days to confirm this, then change the relevant component.

If these do not work.....well......check the hose that's under the throttle body, that fits into the icv. Make sure it is properly fitted, as best as you can. There should be pretty much no wiggle in it.

Poor idle issues can be traced in the following manner. Start the engine, let the engine's note stabilise, then get a can of carb cleaner, and start spraying at possible vacuum leak points. I'm talking the icv area, the throttle body area, the intake manifold gasket area, the vcg vacuum fitting area, around the afm (air flow meter or air mass sensor) etc. If you hit the right spot, the idle will improve...the car will be sucking in carb cleaner, which is flammable, and combustion will improve leading to a better idle. Even if you find a spot, check through everything that you can think of.

I will do a test with a fuel pressure regulator later and let you know if a bad one can cause idling problems and not merely overfuelling ones.


rgds,
Roberto

fryntyr 11-18-2012 06:49 PM

Ok, what I tried today was replace the vacuum line to the fuel pressure regulator. It wasn't in very good shape so I'm not sure if it was leaking but possible. I took it for a drive to get in up to temp and seams to be better. It never died on me at stop signs or idling in gear but this was only one quick drive. It didn't seam to stnnk as much either.

I may be hoping to much that I found the problem, I will let you all know tomorrow after the real test.

The test will be tomorrow when the wife drives it to work and sits at some stop lights.

robertobaggio20 11-18-2012 07:01 PM

Quote:

Originally Posted by fryntyr (Post 7202166)
Ok, what I tried today was replace the vacuum line to the fuel pressure regulator. It wasn't in very good shape so I'm not sure if it was leaking but possible. I took it for a drive to get in up to temp and seams to be better. It never died on me at stop signs or idling in gear but this was only one quick drive. It didn't seam to stnnk as much either.

I may be hoping to much that I found the problem, I will let you all know tomorrow after the real test.

The test will be tomorrow when the wife drives it to work and sits at some stop lights.


It looks like you've found the problem. This would be a new one, at least for me. Proof once again that there is no replacement for one's own hunches and eyeballs. One thing though, before she drives off in the morning, please clear all the error codes first. You can recheck when she gets back and see if the o2 code stays away.

How is the rumble of your idle that you mentioned earlier? Is there any change ?

fryntyr 11-18-2012 07:09 PM

I think it is better, but again, it may be wishful thinking. If the wife comes home tomorrow with a smile and I get lucky, I know it worked. LOL!

I'll go ahead and clear the codes right now and see what happens.

Thanks again

fryntyr 11-18-2012 07:39 PM

OK, reset codes. I went ahead and drove it again but longer and more stops. It runs really good accept It does still have a random miss/stumble at idle. At a few stop signs I felt a hard miss but it didn't die on me. It's not like it has it every couple seconds, maybe a couple times in a full minute. Once when it did it, I think the ICV opened a bit to counteract it because the idle came up immedietly after the miss to 1000 then settled back down.

I wonder if the spark plugs could cause this if they are cheapy brand?

robertobaggio20 11-18-2012 07:56 PM

The gremlin is still out there, but it is now more clearly ignition related. That makes life much easier. And changing the vacuum line was not a waste either.

How old are the plugs ?

A cheapo brand will not cause these problems per se. They just might not be as optimal for your engine as oem ones.

There are two schools of thought on these forums when it comes to plugs. Some people think that the single or dual-claw oem copper plugs are the best. Others prefer to use the 4-claw platinum iridium non management long life spark plugs instead, which last for 100k. Bosch sells both. The price difference between both is insignificant for practical purposes even when you multiply it by 8.

You could also have a leaky valve cover gasket that fills some of the plug wells with oil. When this happens, the ignition charge's delivery is affected. It could produce these symptoms too I suppose. You might want to remove the spark plug concerned and clean it with carb cleaner if the threads are oiled up. The solution is to extract out any oil using cleanex, then eventually get your vcg replaced properly (there are ways to screw up the reinstallation, please use the manual for correct instructions.)

If your spark plugs are old, and your vcg (valve cover gasket) is not leaking, just change the plugs out to a new set. Small money. Even if this does not solve the problem, you are likely to get a slightly improved performance from your engine.

As a worse case scenario, your ignition coil(s) could be busted. They do not always produce a fault code when they are buggy. Bentley has coil resistances that you can check. Check out the low hanging fruit first before you come to this.

fryntyr 11-18-2012 08:02 PM

Will check coils and spark plug boots. It received new plugs just before I got the car, just not sure what brand. I found a download for the Bentley so I'll check the readings for the coils and check them.

Thanks,

mark cherry 11-25-2012 05:29 AM

do remember if it has been running rough this will foul up plugs and fuel mixtures are all over the place and this will cause a miss so clean up the plugs anyhow

fryntyr 12-10-2012 05:28 PM

A littlwe update as I am still fighting this a little. It still has a cough, and sometimes dies when it does this. Really only when it's fully up to temp and only at idle. Otherwise it runs fine and idles smooth(most of the time). Wish I could nail this.

robertobaggio20 12-10-2012 05:47 PM

What have you done so far ? What have you doublechecked ?

fryntyr 12-18-2012 12:39 PM

I think I may have nailed it today.

The last couple weeks I kept thinking about the cough and dieing being worse as it was more up to temp and also about how this car was overheated and had a cracked head prior to my purchasing it.

The Coolant Temp Sensor has a direct influence on fuel mixture so I was thinking with the issue of it being overheated it could have been damaged by the excessive heat. PLus it was one of the only things left I hadn't really replaced or cleaned.

The sensor was only $17.

When I removed it the actual plug-in part seperated from the brass portion and the mating portion was very corroded and rusty where they had been attached. The threads also had some corrosion.

Installed the new one with some antisieze on the threads and some dielectric grease on the plug-in. Reset the codes, and drove it for about a half hour. Not once did it cough or die at idle.

The real test, the wife! She is heading out now and I'll get the results soon. Crossing my fingers, if it's fixed I may get rewarded. LOL!

One other thing I did check was the spark plug boots. They looked ok but I did clean them and used a little dielectric grease inside the boots when I reinstalled the coil packs and boots. Don't know if this contributed but it can't hurt.

BMR_LVR 12-18-2012 12:45 PM

Thanks for the follow up. Good catch. Good luck and I hope it holds up.

robertobaggio20 12-18-2012 12:47 PM

I'm happy that you nailed it but didn't you test the ect by disconnecting it earlier ? Did you doublecheck everything after you sorted out the vacuum lines? Was there a code anywhere (does the stomp test work on your car) ?

fryntyr 12-18-2012 01:33 PM

Rob,
I have a code reader and it always came up as O2 (code FF 46) and reset it often. I reset it this time and it hasn't came back on yet. I'll give it a few days to verify but so far so good.

I disconnected the CTS a while back to see what it did and really didn't change much, maybe even worse.

When I first started sorting this out it originally had a idle that surged up and down. As I found vacuum leaks and cleaned items, it improved to stable but then the cough/die started happening once I did everything else.

The wife just texted me and said ran good, not one cough. Hope it stays that way.

robertobaggio20 12-18-2012 01:52 PM

Quote:

Originally Posted by fryntyr (Post 7257882)
Rob,
I have a code reader and it always came up as O2 (code FF 46) and reset it often. I reset it this time and it hasn't came back on yet. I'll give it a few days to verify but so far so good.

I disconnected the CTS a while back to see what it did and really didn't change much, maybe even worse.

When I first started sorting this out it originally had a idle that surged up and down. As I found vacuum leaks and cleaned items, it improved to stable but then the cough/die started happening once I did everything else.

The wife just texted me and said ran good, not one cough. Hope it stays that way.

...

BMWFatherFigure 12-20-2012 01:33 AM

Love a story where the hero gets nailed by the heroine in the end...............


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