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Rough Idle, slow @ Full throttle


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#1 pavesi

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Posted March 13, 2011 - 11:51 AM

Got my Cayenne 4.5 turbo S a few weeks ago (23k miles) and noticed it idles slightly rough and when given full throttle it seems to take off then get held back, and I hear a funny air type sound around 3000rpm. I ordered 4 new coils ( hoping 4 were ok) took them out and they all look new, certainly no cracks. Ordered ELM 327 code reader the other day, on runing a scan I got code P1090 and looking at the fuel trims, one bank is over 100 in the negaitve suggesting one knackered maf. Looking at real time monitoring I only see one maf reading does the ecu add the 2 mafs togather to calculate over all air flow? I have 2 x recirc dump vlave to fit and 2 new mafs arrived today. Is the above the right way forward?? cheers Paul


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Cayenne Turbo S 521bhp 530lbs torque for now.

www.bmw535d.co.uk

#2 Loren

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Posted March 13, 2011 - 12:42 PM

P1090 Hot film mass air flow meter – below limit value Possible cause of fault - Open circuit in signal wire - Open circuit in sensor voltage - Short circuit to ground in signal wire - Short circuit to ground in sensor voltage - Hot film mass air flow meter faulty - DME control module faulty


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#3 pavesi

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Posted March 14, 2011 - 09:12 AM

Some man, thank you. Replaced both Mafs and dvs today. Very smooth at idle now although I only had it going for a few mins. Will take it for a spin tonight. I cant reset the ecu adaption with my ELM, will prob take the ecu a while to figure out it now had 2 working mafs Not an easy job, would not want to do it again in a hurry.


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Cayenne Turbo S 521bhp 530lbs torque for now.

www.bmw535d.co.uk

#4 pavesi

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Posted March 14, 2011 - 01:39 PM

Had it out for a slow run to allow the ecu to catch up then went for a play. WAY more responsive, feels so much more powerful under light throttle. No hesitation or slowing down on full throttle. Very happy. i still hear a noise change around 4k but I am sure i read somewhere about variable inlet track length not sure if that is the cause. Power is deffo up. My 535d used to hit 121mph on my wee test track ( my bm was very fast) Porker before mafs 117mph Porker new mafs & dvs 119mph. It took 10bhp extra in my bm to get 1 more MPH. So good improvement, not as quick as my bm but getting there. Hopefully should improve my mpg now. average down to 15.9 on an easy run LOL. On my wee spin average was 9.2mpg COOL.


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Cayenne Turbo S 521bhp 530lbs torque for now.

www.bmw535d.co.uk

#5 993BillW

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Posted March 14, 2011 - 04:04 PM

Some man, thank you.

Replaced both Mafs and dvs today. Very smooth at idle now although I only had it going for a few mins. Will take it for a spin tonight. I cant reset the ecu adaption with my ELM, will prob take the ecu a while to figure out it now had 2 working mafs

Not an easy job, would not want to do it again in a hurry.

Scratching my head.... what is a DVS?


Had it out for a slow run to allow the ecu to catch up then went for a play. WAY more responsive, feels so much more powerful under light throttle. No hesitation or slowing down on full throttle. Very happy. i still hear a noise change around 4k but I am sure i read somewhere about variable inlet track length not sure if that is the cause.

Power is deffo up. My 535d used to hit 121mph on my wee test track ( my bm was very fast)
Porker before mafs 117mph
Porker new mafs & dvs 119mph. It took 10bhp extra in my bm to get 1 more MPH. So good improvement, not as quick as my bm but getting there.

Hopefully should improve my mpg now. average down to 15.9 on an easy run LOL.

On my wee spin average was 9.2mpg COOL.

Not going to get 15.9 driving like that... LOL. Must be nice to have your own test track LOL(2)!
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#6 pavesi

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Posted March 14, 2011 - 04:18 PM

Sorry. Dump vales or recic valves. When you take your foot off the throttle there is no-where the the boost to go so the DV or re-circ vale stops the turbo from stalling, and either puts the wasted boost back into the induction system OR if you are 22 years old or younger it goes to atmosphere and makes a whoooooooosh sound. LOL 15.9 was driving at 80mph for around 200miles was expecting around 20-22mpg?? test track Hmmmm, I live WAY up in the highlands of Scotland so plenty test tracks up here :-))


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Cayenne Turbo S 521bhp 530lbs torque for now.

www.bmw535d.co.uk




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