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E34 (1989 - 1995)

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  #1  
Old 08-26-2013, 09:32 AM
E34Addict E34Addict is offline
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Mein Auto: E34 530i '89
E34 M50 Hunting Engine

Hello Everyone
A couple of months ago, I finished an Engine swap from a 1989 6 cylinders M30 engine to a 1992 M50 single Vanos Engine. You can check the swap details at the following thread: http://www.bimmerfest.com/forums/showthread.php?t=618385

I am facing a hunting engine problem again which is very weird.

- If I connect the O2 sensor:
* The hunting is less severe
* I suffer some drop in acceleration
- If I disconnect the O2 sensor (By manually removing the plug from the exhausts):
* The engine's acceleration is better
* The hunting becomes much more annoying
* If I turn the A/C on and while in traffic jam, the hunting is very severe and (from 0.5 to 1.5 RPM) and some times the engine turns off.

In both cases, if I turn the headlights on, I can notice that the hunting slightly increases too.

Error code diagnosis is showing two errors:
1- Air Mass
2- Oxygen sensor heater relay

But I made sure that the Air Mass is fine by trying the following:

1- I got another air mass from another E34 which is working just fine, we cleaned the error codes and tried it on my E34 but the same behavior and same error codes showed again
2- We tried my Air mass on the other car and it worked fine and no error codes or change in behavior was noticed.

Your help is highly appreciated.
Thanks
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Last edited by E34Addict; 08-26-2013 at 09:34 AM.
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  #2  
Old 08-26-2013, 09:49 AM
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Monsignor Monsignor is offline
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I'm not sure what "Hunting" is...?
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  #3  
Old 08-26-2013, 10:36 AM
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BMWFatherFigure BMWFatherFigure is offline
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Rythmic increase and decrease in idle rpm. Often with mixture changes in an EFI equipped car. Just a rich mix on a carbi car. Glad to help, Monsignor.
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  #4  
Old 08-26-2013, 11:48 AM
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^ Much obliged FF

I would suspect a power supply issue, if not a faulty DME looking for proper fuel inputs.

Have you tried replacing the o2 sesnor rather than just connect/disconnect? If it can find an accurate exhaust reading it'll find a happy idle medium via injectors/DME
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  #5  
Old 08-26-2013, 11:50 AM
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BMR_LVR BMR_LVR is offline
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I would recommend checking and/or cleaning the ICV. Also look for vacuum leaks.
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Calypso Red 1992 525i with 200K miles

1991 735i - Sold
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  #6  
Old 08-26-2013, 11:54 AM
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Steve, I thought that initally as well, except those are fundamentally mechanical-based issues. OP states variances in performance and idle quality with and without the Sensor removed. There must be some input or reading that is being dropped or misread, rather than ICV working improperly. Food for thought? This is also coming from somebody who just now learned what "hunting" is
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  #7  
Old 08-30-2013, 02:30 AM
E34Addict E34Addict is offline
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Quote:
Originally Posted by Monsignor View Post
^ Much obliged FF

I would suspect a power supply issue, if not a faulty DME looking for proper fuel inputs.

Have you tried replacing the o2 sesnor rather than just connect/disconnect? If it can find an accurate exhaust reading it'll find a happy idle medium via injectors/DME
I don't think it is a matter of O2 sensor because by theory, if the O2 sensor is disconnected and no more readings are being transmitted to the DME, then the DME deals with this case by suggesting a stable default exhaust reading value. Accordingly, if it was the O2 sensor, disconnecting it must cause the hunting to disappear.
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  #8  
Old 08-30-2013, 02:40 AM
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Quote:
Originally Posted by BMR_LVR View Post
I would recommend checking and/or cleaning the ICV. Also look for vacuum leaks.
I checked the ICV and it is working fine.
I have one more finding which made things not making sense at all to me. On my way to work this morning, I had the A/C on and the road was a little steep, and there was a traffic jam where we were barely moving. So I shifted the transmission to "Neutral" and rolled slowly with traffic:

1- When the car completely stops, the RPM idles at around 0.8 and remains stable.
2- When I remove my foot off the brake pedal and the car starts rolling slowly while on "Neutral" gear (Not hitting the gas pedal at all), the engine starts hunting. The RPM idles back at around 0.8 when the car completely stops.

What the hell has the hunting engine to do with the vehicle moving or stopping on Neutral gear and without even touching the gas Pedal??? I am totally lost.
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  #9  
Old 08-30-2013, 03:03 AM
kmorgan_260 kmorgan_260 is offline
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This still makes me suspect the ICV or vacuum problem. The ICV is supposed to regulate the idle when things like the AC, power steering, alternator, etc place varying loads on while at idle. Maybe pressing and releasing the brakes is changing the vacuum and the ICV is trying to compensate.
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  #10  
Old 08-30-2013, 10:21 PM
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Brake applied or not - could it be a leak in the brake servo??
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  #11  
Old 09-02-2013, 01:19 AM
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Quote:
Originally Posted by BMWFatherFigure View Post
Brake applied or not - could it be a leak in the brake servo??
1- If this the case, I should at least feel that the brake pedal is more rough to press but this is not my case.
2- The engine is hunting when the vehicle rolls slowly on neutral with no brakes applied, and not when it is stopped with the brakes applied.

Anyway, I will check the servo and all the hoses this afternoon to make sure that there is no leak at all. Would an exhaust leak lead to such behavior too?
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  #12  
Old 09-02-2013, 08:47 AM
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Quote:
Originally Posted by E34Addict View Post
1- If this the case, I should at least feel that the brake pedal is more rough to press but this is not my case.
2- The engine is hunting when the vehicle rolls slowly on neutral with no brakes applied, and not when it is stopped with the brakes applied.

Anyway, I will check the servo and all the hoses this afternoon to make sure that there is no leak at all. Would an exhaust leak lead to such behavior too?
The booster operates off of vacuum no?

I never saw where you definitively ruled out a vacuum leak. Have you done so by means of the smoke test?
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Quote:
Originally Posted by noego View Post
It's Deja Poo - as in, I've heard this **** before.
Steve

Calypso Red 1992 525i with 200K miles

1991 735i - Sold
1992 525i - Sold
1995 325is - Sold
2000 528i - Sold

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  #13  
Old 09-02-2013, 09:24 AM
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Quote:
Originally Posted by BMR_LVR View Post
The booster operates off of vacuum no?

I never saw where you definitively ruled out a vacuum leak. Have you done so by means of the smoke test?
I did not rule out the vacuum leak in general yet. What i ruled out is the servo leak as what i am trying to say is that if there was any leak in the braking system overall, the brake pedal will be more rough to press and the brakes' behavior and performance will be affected clearly (I never noticed any issues in the brakes). Isn't that right?

One more thing, what is the smoke test?

P.S: Whether the hunting issue solved or not, I would like to thank you guys for your continuous help and support
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  #14  
Old 09-02-2013, 10:06 AM
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  #15  
Old 09-05-2013, 05:30 AM
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I did not have time to do the smoke test yet but things are starting to get more serious. I noticed additional symptoms but i am not sure if all related to the same problem or not:

1- Sometimes, I can hear a rattling-like sound when i accelerate up hill and the RPM goes beyond 2500.
2- Sometimes, i notice some very quick not-dense white smoke coming out of the exhausts at early stages of acceleration and goes away immediately. This is clearly an improper fuel combustion issue. I will be doing the smoke test the soonest as i have strong doubts that there is a vacuum leak some where that is messing up the whole system (I am suspecting the intake manifold gasket)

Should those additional symptoms change anything in my diagnosis? Shall i do additional tests after doing the smoke test?
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  #16  
Old 10-06-2013, 03:34 AM
E34Addict E34Addict is offline
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Re: E34 M50 Hunting Engine

Hi guys. I did the smoke test and there aee no vacuum leaks. I took the car to a bmw expert and he assured me that the icv that is fitted in is not for my engine. He said that he is certain that if I get the correct icv the problem will go away. Now, I researched a little bit and learned that there are some black and silver icv for the m50 engines. I tried to get the correct part number but I am a little bit lost. To remind, I have the 1992 M50TU engine with vanos. Can anyone shortly brief me on how to get the correcr icv? Is it the silver or the black one? And is there any link for me to get the part number? Thanks

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  #17  
Old 10-06-2013, 07:38 AM
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Quote:
Originally Posted by E34Addict View Post
Hi guys. I did the smoke test and there aee no vacuum leaks. I took the car to a bmw expert and he assured me that the icv that is fitted in is not for my engine. He said that he is certain that if I get the correct icv the problem will go away. Now, I researched a little bit and learned that there are some black and silver icv for the m50 engines. I tried to get the correct part number but I am a little bit lost. To remind, I have the 1992 M50TU engine with vanos. Can anyone shortly brief me on how to get the correcr icv? Is it the silver or the black one? And is there any link for me to get the part number? Thanks

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Here in the states, the M50TU with vanos didn't start until 93. One of the most useful sites to find part numbers is realoem.com. Note that the E34 is now in the archived section. You simply plug in the VIN information required (I think it's the last 7 digits) and it will show every part number that is specific to your car...... if it works for the non-US models. I think it does though.

Hope this helps.
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Most problems are usually something simple !

Quote:
Originally Posted by noego View Post
It's Deja Poo - as in, I've heard this **** before.
Steve

Calypso Red 1992 525i with 200K miles

1991 735i - Sold
1992 525i - Sold
1995 325is - Sold
2000 528i - Sold

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  #18  
Old 10-07-2013, 07:45 AM
E34Addict E34Addict is offline
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Quote:
Originally Posted by BMR_LVR View Post
Here in the states, the M50TU with vanos didn't start until 93. One of the most useful sites to find part numbers is realoem.com. Note that the E34 is now in the archived section. You simply plug in the VIN information required (I think it's the last 7 digits) and it will show every part number that is specific to your car...... if it works for the non-US models. I think it does though.

Hope this helps.

Thank you for your support as usual BMR_LVR. The VIN number doesnt help me in my case because my car used to be an Automatic European 6 Cylinders 1989 530i and it is now a manual 1992 525i with M50TU Vanos engine. Anyway, I checked the website and got the part number of the ICV which is: 13411744713. I will one and fit it in. I will keep you updated if this fixes my problem or not. Thanks again
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Old 10-07-2013, 08:14 AM
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Originally Posted by E34Addict View Post
Thank you for your support as usual BMR_LVR. The VIN number doesnt help me in my case because my car used to be an Automatic European 6 Cylinders 1989 530i and it is now a manual 1992 525i with M50TU Vanos engine. Anyway, I checked the website and got the part number of the ICV which is: 13411744713. I will one and fit it in. I will keep you updated if this fixes my problem or not. Thanks again
Wow. You truly have a FrankenBimmer there I would think that the ICV for the M50 with vanos and without vanos would be the same, but I would check the part numbers to be sure.
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Most problems are usually something simple !

Quote:
Originally Posted by noego View Post
It's Deja Poo - as in, I've heard this **** before.
Steve

Calypso Red 1992 525i with 200K miles

1991 735i - Sold
1992 525i - Sold
1995 325is - Sold
2000 528i - Sold

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  #20  
Old 10-07-2013, 07:41 PM
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M540FELLA M540FELLA is offline
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Clogged cats/bad o2 sensors would give you that rattle you described.
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Old 10-09-2013, 05:19 AM
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Originally Posted by BMR_LVR View Post
Wow. You truly have a FrankenBimmer there I would think that the ICV for the M50 with vanos and without vanos would be the same, but I would check the part numbers to be sure.
Yes indeed i do . But why did you seem surprised?? You participated a lot in the thread that i created which went through the swap process.

Anyway, I installed the new ICV about an hour ago and made sure that all the hoses and seals are good and no leaks what so ever. When i first turned the engine on, it took some time to reach a stable idle. Then, after it idled, every time after i hit the throttle from under the hood and release it , the engine starts hunting for idle again and takes around 5 seconds to stabilize. However, on my way to work, the engine did not hunt at all and the RPM was stable all the way. I will do some more test drives to see if things are fine now or not.
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Old 10-09-2013, 05:20 AM
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Originally Posted by M540FELLA View Post
Clogged cats/bad o2 sensors would give you that rattle you described.
Thanks for the tip. The cats have been changed a while ago and they are good. My next action on the list is changing the O2 sensor.
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  #23  
Old 10-09-2013, 05:57 AM
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Originally Posted by E34Addict View Post
Yes indeed i do . But why did you seem surprised?? You participated a lot in the thread that i created which went through the swap process.
The ol' memory aint what it used to be
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Most problems are usually something simple !

Quote:
Originally Posted by noego View Post
It's Deja Poo - as in, I've heard this **** before.
Steve

Calypso Red 1992 525i with 200K miles

1991 735i - Sold
1992 525i - Sold
1995 325is - Sold
2000 528i - Sold

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  #24  
Old 10-10-2013, 05:35 AM
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Re: E34 M50 Hunting Engine

This hunting just refuses to go away. After installing the new ICV, the engine performance is better and hunting is now showing only in one case:

while stopping on neutral gear, i hit the gas pedal until the rpm goes high. When I remove my foot completely off the gas pedal where the engine's rpm reached above ~ 4500, the rpm will drop all the way down till it is almost dead and then hunting will become severe and the engine won't idle unless I put my foot on the gas pedal again and press slightly then remove my foot. The rpm will then idle correctly in about 5 seconds and remains stable. In general, I can say that the rpm is severely hunting if dropping from high revs. Sorry for extensive explanation but I dont know how to describe it otherwise.

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Old 10-17-2013, 08:44 AM
E34Addict E34Addict is offline
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Re: E34 M50 Hunting Engine

I removed the new ICV, cleaned the old one very well and put it back in, everything is back to normal. Thanks for your help guys. My problem therefore was a dirty ICV. But what is not convincing at all was the symtpoms changing with and without the o2 sensor tests done initially. Now with the o2 sensor connected amd the icv clean, I will do the o2 sensor disconnection test again and try to check if that needs to be replaced as well.

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