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Discussion Starter · #1 ·
this has happened to me a couple time. when under hard acceleration, just before you hit the limiter, the engine just jirks once like it did hit the limiter, but then loses all power. i have to come to a stop and restart it or turn the car off and on to get the power back. has anyone had similar problems?
 

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If this is happening in 1st gear, it could be the well known "tach lag" that occurs in most M5s in 1st gear. Essesntially the true 7000 rmp limiter is hit at about 6500-6600 indicated in 1st gear. This does not usually occur in the other gears.

If the engine otherwise feels fine and pulls to 7000 in second gear, just shift at 6500 in 1st.

There is much information on this if you do a search.
 

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I don´t think that is the problem, as he says he has to stop and restart to fix it. Sounds more like the engine goes into one of the limp-home-modes.

I´d check for fault-codes.

David
 

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Discussion Starter · #4 ·
i don't think that it happens in first. i happened to me on the highway a few times, i was in third at the time. i now have a SES light that comes on and off daily. on monday it was on, tuesday it was off, and yesterday on again. when i checked it on monday the tech said it was the speed sensor. it seems to me that i could be a software problem, not the engine because it pulls fine untill almost readline.
 

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ContractR said:
i don't think that it happens in first. i happened to me on the highway a few times, i was in third at the time. i now have a SES light that comes on and off daily. on monday it was on, tuesday it was off, and yesterday on again. when i checked it on monday the tech said it was the speed sensor. it seems to me that i could be a software problem, not the engine because it pulls fine untill almost readline.
Sounds like MAF's are broken!

KIP
 

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Discussion Starter · #6 ·
i thought it was the maf's too, but the dealership checked them said they were ok. in otherwords, they hooked up the comp to check if there was a code and that's it. back when i had the s4, i took it to the stealership a few times to check for a boost leak and everytime they told me that it was ok. it was nice to find out that my turbo blew because i was driving around with a boost leak afterwards:mad:

how can i check the mafs myself
 

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ContractR said:
i thought it was the maf's too, but the dealership checked them said they were ok. in otherwords, they hooked up the comp to check if there was a code and that's it. back when i had the s4, i took it to the stealership a few times to check for a boost leak and everytime they told me that it was ok. it was nice to find out that my turbo blew because i was driving around with a boost leak afterwards:mad:

how can i check the mafs myself
I have no idea, but there was this guide on cleaning them:

http://www.louv.tv/cars/m5/MAF/

hope it helps...
 

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MAF testing

ContactR,

The MAFs have to be _really_ bad before you get a stored fault-code.

The functional test by the BMW tester just tests the MAFs at idle with the car standing still. IMH experience that says absolutely nothing about how they perform at WOT.

To perform a test yourself:

1. Get a graphing and data-logging OBD-II scantool. If you already have a laptop PC, it will cost you about US$ 100 to buy one. Worth every cent. (I use the one called "ISO" from www.odb-2.com which I am very pleased with)

2. Plug it into the car and go for a drive

3. Look at the graph for CLV (calculated load value). This is basically the MAF signal expressed in percent of the expected maximum at each RPM.
When you accelerate WOT this number should immediately go to 100% and stay there until you release the throttle or hit the rev-limiter .

4. If the CLV reading it is low at all RPMs, try new air filters.

5. If it is ok at low RPMs, but lower at higher RPMs, try the MAF cleaning procedure as posted above, and the retest immediately. If this improves the numbers you know 100% there is (or if the cleaning was very successful used to be) a MAF problem. This does not say it is the only problem, but the car can never run better than its MAFs.

Hope this helps!

David
 

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BTW ContactR,

What year and how many miles?

The older M5s have poor cam sensors, which later got redesigned. The old ones simply will fail, it seems. Just a matter of when. So if the mechanic wants to replace those sensors now, it will not be a waste of money even if it should later proove not be strictly necessary right now.

The MAFs seem to last about 50-60000 miles.

David
 

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ContractR said:
i don't think that it happens in first. i happened to me on the highway a few times, i was in third at the time. i now have a SES light that comes on and off daily. on monday it was on, tuesday it was off, and yesterday on again. when i checked it on monday the tech said it was the speed sensor. it seems to me that i could be a software problem, not the engine because it pulls fine untill almost readline.
Try pulling the ABS fuses, 17 and 30 (from memory). I think that will disable the speed sensor that senses the difference in speed between front and rear wheels and shuts down the car. They need to be pulled for dyno runs. It is easy to do, no $$$ involved and you get to go on another "test run" to check it out!!! :1:
Regards,
Jerry
 

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Discussion Starter · #11 ·
thanks guys, my car is 2001 with 51,xxx miles. i will do what you suggested to see if it's any better. got to get my car to perfect running condition by 5/31/05. i have a showdown with a C4S on the track that day.
 

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if you're getting ses lights, there must be codes stored, i think you dealer needs to do a little more work. there are just too many possible things to throw parts at the car in hopes of a cure. From basic maintanance, plugs, fuel filter etc to mafs, cps, vanos etc.
Mike
 

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gsfent said:
Try pulling the ABS fuses, 17 and 30 (from memory). I think that will disable the speed sensor that senses the difference in speed between front and rear wheels and shuts down the car. They need to be pulled for dyno runs. It is easy to do, no $$$ involved and you get to go on another "test run" to check it out!!! :1:
Regards,
Jerry
Good idea, just remember that the car will behave _very_ much different without ABS and DSC.

David
 

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Howzit ContractR,

Did you ever find a solution to this problem? I am experiencing exactly the same problem with my car.

Please help,

Rudi


ContractR said:
this has happened to me a couple time. when under hard acceleration, just before you hit the limiter, the engine just jirks once like it did hit the limiter, but then loses all power. i have to come to a stop and restart it or turn the car off and on to get the power back. has anyone had similar problems?
 

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Discussion Starter · #15 ·
i'm suppose to have it checked tomorrow. i will post here when i know the cause.



imolaman said:
Howzit ContractR,

Did you ever find a solution to this problem? I am experiencing exactly the same problem with my car.

Please help,

Rudi
 
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