Need some guidance from those more mechanically minded than myself... - BMW M5 Forum and M6 Forums
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post #1 of 13 Old 6th June 2019, 10:30 AM Thread Starter
SeeSure
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Need some guidance from those more mechanically minded than myself...

Over the last week or so, intermittently, my car has felt sluggish and not responsive at times.

Usually I've noticed it from cold as the get up and go is not there and throttle response is lack lustre to say the least. Other times it's been spot on.

3 or 4 times now when I've pushed a little as soon as the car hits around 4k revs in 3rd gear it's like I've hit the rev limiter hard and the car loses ALL power and slows to around 30-40 mph and the engine feeling as though it's going to jump out of the bay as it's almost as though all timing has gone, it's lumpy as hell.

Yesterday it happened a couple of times, plus at one point I had to drop from 6th to 3rd on what was really only a gentle upwards incline, a hill I'd normally take in 6th and accelerate up.

Also from a set of traffic lights yesterday the car was fully out of puff in 1st gear at 2k revs.. it's like it's severely restricting performance.

Anyway I've pulled the codes with my Peake Code Reader even though the EML has not come on.

74 - Servotronic valve current
AA - Secondary air system, flow too low... not worried about that as happens on virtually every car
29 - Air mass sensor, Cyl #1-4
81 - Catalyst protection engaged, fuel tank low - Odd one as I've not let the car dip below 80 miles range on the OBC for several years
90 - Fuel control, Cyl #1-4
91 - Fuel control, Cyl #5-8

Would I be right in assuming the MAFs are the culprit?

Guidance sought from the knowledgeable please.

Why is the slowest person always at the front of the queue ???



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post #2 of 13 Old 6th June 2019, 11:20 AM
Rosie
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Sounds like the MAFs - particularly with that code.
Unplug them and drive the car - if it goes how it should then they’re the problem.
Also Euro spec S62’s won’t turn the engine light on as readily as the US spec cars.
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post #3 of 13 Old 6th June 2019, 04:04 PM
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Garage
*With the car off

Quote:
Originally Posted by Rosie View Post
Sounds like the MAFs - particularly with that code.
Unplug them and drive the car - if it goes how it should then they’re the problem.
Also Euro spec S62’s won’t turn the engine light on as readily as the US spec cars.
100% agree. The nuance is to unplug them with the engine off, then run it.

This is the best option for MAFs I have found:
BMW 5 Series E39 M5 (00-03) Air Mass Flow Sensor (MAF) by BOSCH - F 00C 2G2 029 (PAIR) : Bimmerzone.com

2002 Beast Schwarz-Metallic/Blk Sport
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post #4 of 13 Old 7th June 2019, 10:15 AM Thread Starter
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Quote:
Originally Posted by KrautHammer View Post
100% agree. The nuance is to unplug them with the engine off, then run it.

This is the best option for MAFs I have found:
BMW 5 Series E39 M5 (00-03) Air Mass Flow Sensor (MAF) by BOSCH - F 00C 2G2 029 (PAIR) : Bimmerzone.com
Well I had already bought a couple of MAFs as I suspected something was amiss with them as it doesn't feel like the CPS loss of power symptoms.

I dropped them in last night and started the car, at first it was as lumpy as hell very slow throttle response and rev pick up. After about 5 minutes or so the revs evened out and throttle response appeared good sitting on my driveway. I'll be taking it out for a 60 mile run this evening which will be a good mix of motorway and fast minor road.

Thanks for the link - I'd spotted Bimmerzone on my Google searches but couldn't see information on the import tax liability which stings sometimes, however for UK based people I'll leave this link for MAF suppliers in the UK - Although they did actually get posted from Germany and took a week to arrive with DHL.

https://www.cartech-one.co.uk/en/sea...air-mass-meter

Why is the slowest person always at the front of the queue ???



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post #5 of 13 Old 7th June 2019, 03:55 PM
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Classic bad MAFS. The dirty sensors cause incorrect estimate of air flow so ECU pulls fuel until it hits threshold causing the fuel control codes. The O2 sensors see the lean AF mixture which causes the low fuel code (goofy translation from German).
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post #6 of 13 Old 7th June 2019, 08:02 PM
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Don't be surprised if you get two new codes. It is just a result of the fuel trim swinging back to where it should be in a hurry. Clear them and continue until you have a couple hundred miles on them. After that time the adaptions will have settled and you can trust any new codes.
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post #7 of 13 Old 10th June 2019, 02:40 PM Thread Starter
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Well I managed to clock up about 130 miles over the weekend, the first 100 or so miles I had to take it really easy, the car was incapable of any "normal" performance.

I had to short shift when pulling away to prevent limp mode kicking in and used cruise control to keep it steady on the motorway and not gov over 4k revs.

Last night, after about 120 miles I gave it some beans and it seemed ok. So I took it out again this morning to check and it does look like normal service has resumed....

Cleared a couple of codes which appeared (AE & AF Air fuel Adaptions) so will see how things go

Thanks all

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post #8 of 13 Old 14th June 2019, 08:05 PM Thread Starter
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Well that lasted 5 days .... worse than ever today to the point that I had to stop the car and restart it as I couldn't get up a small slope, seems like 2k revs is the limit in any gear now... codes this time are 90, 91 and OC...

I managed to get to where I was going and tried to rev the car but it sounded like half the cylinders had packed up and it was hunting up and down and after a few seconds it cut out.

It was fine when I first set out happily cruising at 90mph but eventually I came in to town and hit slow traffic, after about 20 minutes in the slow traffic is when I felt the car lurch and it sounded like it was struggling to breath....

Will ring my indy on Monday to book it in, but in between times I need to figure how to get it to him from where I am... approx 100 miles away from him...

Why is the slowest person always at the front of the queue ???




Last edited by SeeSure; 14th June 2019 at 08:35 PM.
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post #9 of 13 Old 15th June 2019, 03:18 AM
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Unplug the MAFs and drive it. Go around the block a few times to see if it will balance, but depending on what is wrong it might give you enough.
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post #10 of 13 Old 17th June 2019, 12:29 PM Thread Starter
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Update...

Car had to be trailered 70+ miles on Saturday night and be left at my garage for them to look at today or tomorrow.

I was on my way home and struggled to keep the car running at times with minimal power, called the breakdown company and they had a look and read the codes and got pretty much what I did - namely 02 sensor (Peake Code OC), I also saw another code, Peake Code D1, which is a mis-fire on cyl 5 during warm up.

I managed to park up in a retail outlet carpark and when the recovery truck arrived he started the car and it idled pretty evenly while he read the codes, he then asked me to take the car around the lot and give it some beans... but nothing doing as soon as the throttle was pressed it all went to crap ...

He was surprised that an O2 issue could cause such a big issue, and said it could be a bad knock sensor retarding the engine along with a failing / failed coil pack.

I'll keep this updated once I get news back from my Indy...

Why is the slowest person always at the front of the queue ???



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