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Discussion Starter #1
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. :)
 

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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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*With the car off

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
 

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Discussion Starter #4
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/search/v-10300/n-386/bmw-5-air-mass-meter
 

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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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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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Discussion Starter #7
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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Discussion Starter #8 (Edited)
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...
 

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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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Discussion Starter #10
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...
 

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How long can you run without the MAF's and not cause any harm to anything?

Mine has been experiencing very slight losses of power, but it's more like when I stomp on it, the power I expect isn't there, it's lessened. When I feel the power the way it should be in that band, it's nuts, so there are definitely many times when I demand the power and it's just not there the way it should be. No codes related to anything MAF or otherwise right now.

97K miles, unsure if MAF's have ever been changed and that goes for the CPSs and TPSs too. But as noted, not getting any codes, and I would expect a code if it was related to one of these electrical components.
 

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Lack of power intermittently sounds like CPS need replacing. If you have original CPS they can be almost dead before they throw a code.
To your question you can run with the MAFs unplugged forever as long as you pay attention that the DME does not get an air temp from the MAFS anymore.
 

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Discussion Starter #13 (Edited)
To finish this off :

After almost 3 weeks I picked my car up yesterday and ragged the nuts off it !!! All seems good although at one point in traffic the temperature gauges started to creep past mid point, I'll have to keep an eye on that although I did have a new water pump fitted about 2-3 years back...

Anyway to round off, my Indy struggled with this as the only codes he could find were the same as I'd got along with a fuel pump code. So he changed the fuel pump and nothing improved.. so he took the fuel pump off and fitted it to another car and it worked fine on that...

MAFs I'd changed with Bosch ones from Germany with the correct serial numbers for our cars.

Front O2 sensors had been replaced last year so he doubted it was those.

Having cleared the codes initially he struggled to find any more information so it was a case of guess work as the car was now only starting and then almost immediately stalling.

Symptoms really didn't appear to tie in with bad CPS as I've experienced those in the past and would have picked up on it way back.

Anyway we had a really good chat about what I'd experienced and how it felt etc and we went through various ideas, such as plugs, coils, injectors, vacuum leak, vanos solenoids and so on...and one by one we discounted them, the bottom line was that it felt like fuel starvation but originally only under certain conditions which were usually when pressing on hard, overtaking and leaning on the throttle heavily.

So back to the fuel supply and a close look at the fuel filter and wallah, we found upon close inspection it was partially blocked and restricting fuel to the pump which had been working overtime and we think was intermittently curling up and almost dying.

In summary - after a new fuel pump, fuel filter, fuel tank sensor and a pressure valve have been fitted warp speed is back on tap...

Sadly though the total bill came to £2.70 less than a 2003 C200 Kompressor with 90k miles on the clock cost me to buy to run around in whilst my M was off the road...
 

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