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7 Series - E38 (1995 - 2001)

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  #1  
Old 11-06-2013, 07:16 AM
Vitaliy273473 Vitaliy273473 is offline
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Mein Auto: 1998 740il
98 740il engine shakes when starting

Hello, I have 98 740il and when you go to start the car the engine shakes like the idle is to low and car is about to die. Not sure if this has anything to do with this problem but I have the check engine light on with codes po170 and po173. Also When the car is not fully warmed up and you put in gear and push the gas pedal the car will sit there for 2-3 seconds and finally drive. I'm new to bmw's and I'm not sure if these issues are relevant or not. So I apologize in advanced and appreciate any help and advice I can get. Thanks guys!


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  #2  
Old 11-07-2013, 06:23 AM
ou18 ou18 is offline
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unless i did my search incorrectly, these codes identify unmetered air leaks and fuel mixture to lean. Which would cause your rough idle.

Could be a few different things. Leaky throttle body gasket, bad maf, wholes in the air duct from maf to throttle body. Bad inake mani gaskets. Check all the plumbing work to the throttle body top and bottom.
Easiest way to find it is, get some throttle body cleaner, turn the engine on, and start spraying around those areas. Also check the rear intake mani cover on the back. That too has a gasket between it and the manifold. Check where the intake mani attaches to the engine, there are gaskets between it and the block as well.
if the idle changes you have an air leak that isnt being metered by the maf.. causing the engine to run rough..

When mine ran rough, i was leaking air at the throttle body gasket. Where it attaches to the intake mani. When i changed it, it crumpled in my hand. It should be pretty soft and pliable.
You can also get some maf cleaner and clean the maf as well and see if that helps at all.

Also check the idle air control valve and its grommet for leaks.

here is a good link for you to check out for areas of interest...

http://forums.bimmerforums.com/forum...-2-Malfunction
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Last edited by ou18; 11-07-2013 at 06:33 AM.
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  #3  
Old 11-08-2013, 01:44 AM
Vitaliy273473 Vitaliy273473 is offline
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Mein Auto: 1998 740il
98 740il engine shakes when starting

Thanks for your help! But it only idles rough when the engine is cold. Wouldn't it have a rough idle all the time if I had an air leak?


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Old 11-08-2013, 03:07 AM
ou18 ou18 is offline
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Re: 98 740il engine shakes when starting

Depends on how bad the gaskets are.if thats the issue.as the engine heats up the gaskets may seal up and expand just enuff to stop the air leak..when cold they contract back....

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  #5  
Old 11-08-2013, 05:43 AM
Vitaliy273473 Vitaliy273473 is offline
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98 740il engine shakes when starting

That it is true. I didn't think about that. Thanks for your help. Il try looking for a leak tomorrow and let you know how it goes


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  #6  
Old 11-08-2013, 05:55 AM
ou18 ou18 is offline
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Throttle body cleaner will help diagnose the issue if you have a leak. You'll notice a definite change in idle if the cleaner gets passed a gasket, it will smooth out briefly and then go back to running rough...
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  #7  
Old 11-08-2013, 06:21 AM
Vitaliy273473 Vitaliy273473 is offline
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98 740il engine shakes when starting

Ok thanks for that! I was actually gonna spray it on when the motor was warm but spraying it on when it's idling rough seems like it would be easier to hear when the motor is running fine then the rpms picking up.


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  #8  
Old 11-08-2013, 07:03 AM
ou18 ou18 is offline
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That would be the way i would do it, spray while running rough, and listen for changes in idle. If you do it while its warm, those gaskets may have expanded already...
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  #9  
Old 11-08-2013, 07:21 AM
Vitaliy273473 Vitaliy273473 is offline
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98 740il engine shakes when starting

That is very true. Il do it tonight after work Andrey you know if I find anything. Thank you so much for your advice


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  #10  
Old 11-08-2013, 09:01 AM
Vitaliy273473 Vitaliy273473 is offline
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98 740il engine shakes when starting

That is very true. Il do it tonight after work Andrey you know if I find anything. Thank you so much for your advice


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  #11  
Old 11-10-2013, 01:16 AM
Podmore Podmore is offline
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Also pull your plugs and see which ones are oiling up. Misfiring / shaking may also be due to one or two plugs not firing correctly, and they will tend to be sooty. Check for oil contamination on the plug insulators due to leaking valve cover gaskets too.
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Old 11-10-2013, 03:06 AM
ou18 ou18 is offline
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Re: 98 740il engine shakes when starting

Ahhhhhhhh yes...the good old valve cover gremlin...

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  #13  
Old 11-11-2013, 12:24 AM
Vitaliy273473 Vitaliy273473 is offline
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98 740il engine shakes when starting

Wouldn't oil in my plugs cause oil loss?


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  #14  
Old 11-11-2013, 04:58 AM
ou18 ou18 is offline
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unless you are leaking like a strainer. You can tell if your valve covers are leaking, shine a like down in there if you see oil pooling in the plug wholes , time to replace the gaskets...which is a pretty easy job. Definitely a DIY job.
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  #15  
Old 11-19-2013, 01:49 PM
sas_man sas_man is offline
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Mein Auto: 1998 740iL
This worked for me.

I too have a 98 740iL. It had thrown codes P0170 & P0173. The idle when cold was really off, it reminded me of my Dad's old 1966 chevy impala with and engine twice the size of this one. Anyway, my fix was real simple. On mine, the band clamp on the down wind side of the MAF had gotten really loose on the intake boot (part number 13 71 1 432 410). The boot actually wiggled freely. This led the computer to think it was getting less air than it really was. The engine compensated by causing the injectors to remain open longer than necessary, thus 'running too rich'. I could smell gas when it idled.

After I snugged the boot clamps down, the idle smoothed out nicely and I got about 2 MPG increase immediately. Sometimes its the real simple stuff. Now if I could just figure out that vehicle speed sensor problem.
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