Is this a MAF issue?

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tontonjon
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Is this a MAF issue?

Post by tontonjon »

Next on the list of onethingafteranother is that all of a sudden the C5, with renewed suspension and no airbag fault warnings, has lost its power uphill.

Symptoms, when losing speed uphill I push the accelerator to the floor, but there's no response (it's OK-ish on the flat);
more smoky than usual, especially when cold;
occasional smell of unburned diesel just after the engine stops.

The last time I had a loss of power like this, it was cured by a new MAF meter/sensor and I am likely to fit one anyway. But what else could I check (without diagnostics!) in the meantime?

And does anyone have experience of the manufacturer Bölk? Their MAF is a fraction of the proce of VDO, Hella or Lucas - and there may be a reason for this...
Peter.N.
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Re: Is this a MAF issue?

Post by Peter.N. »

Try unplugging the MAF, if it makes no difference its probably faulty. The typical symptom of MAF failure is lack of power below 2000 rpm, once above that its OK.

One of my 406's recently had the same problem only with very little power below 2000 rpm and it turned out to be a faulty vacuum pump, it was also affecting the brakes but not a great deal. Check the vacuum pipes between the solenoids behind the top of the engine - at least that's where they are on the 406, they can leak and that will cause lack of boost.

The advantage of having two cars the same is that you can swap parts about to check, see if you can borrow one, its not the same as the 406 though, slightly bigger.

Peter
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tontonjon
Posts: 79
Joined: 25 Dec 2014, 19:28
Location: South West UK
My Cars: Deep Purple Mk2 Cactus manual and Emerald Blue Mk2 Cactus automatic
Used to own 1970 DSuper and 2003 C5
x 7

Re: Is this a MAF issue?

Post by tontonjon »

Yes, below 2000 there's no response to an accelerator press, but above 2000 there's a sudden surge, like a turbo cutting in. I'll see if I can find the vacuum pipes and hope it's not the pump!

Thank you!
Peter.N.
Moderating Team
Posts: 11563
Joined: 02 Apr 2005, 16:11
Location: Charmouth,Dorset
My Cars: Currently:

C5 X7 VTR + Satnav Hdi estate Silver
C5 X7 VTR + Hdi Estate 2008 Red

In the past: 3, CX td Safaris and about 7, XM td estates. Lovely cars.
x 1199

Re: Is this a MAF issue?

Post by Peter.N. »

Sounds like a vacuum problem, check all the rubber pipes from the pump which is on the passenger side end of the head, its easy enough to change once you have all the pipes out of the way. I have a scrap car which I nicked mine from - 246k miles and the pump is still good! You should be able to get a second hand one for not to much money, they are usually OK.

Peter

https://www.ebay.co.uk/itm/ref-181-01-P ... 0705.m4780
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tontonjon
Posts: 79
Joined: 25 Dec 2014, 19:28
Location: South West UK
My Cars: Deep Purple Mk2 Cactus manual and Emerald Blue Mk2 Cactus automatic
Used to own 1970 DSuper and 2003 C5
x 7

Re: Is this a MAF issue?

Post by tontonjon »

Forgot to post a conclusion!

MAF sensor replaced, car back to normal.
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