matt077

iTrader: (2)

hi all

my car as started to be jumpy on full boost, it as started to cut out at times at lights or idle very low. also the check engine light flashes on full boost (tho apexi don't report a knock)

I'm starting to think that its my maf which needs replacing?

any help be great guys

Brun

If you suspect the maf FFS, don't boost. It can end your engine!!!!!
Unplug the maf when the engine is running and see if anything changes. If nothing does then that's the culprit!
What car? How old is current maf?

matt077

iTrader: (2)

i can have the car running and unplug the maf and the car cuts out with in 2-3sec, its a version 6 1999 mate

i've had the car about 5 months and i've not changed it yet (dont know the last time it was swapped) i cleaned it before i had it mapped which was about 1 and half ago now

chocolate_o_brian

iTrader: (22)

V5 was my99, V6 was my00

Both are known for weak mafs.

Knock sensor??

Brun

If the age of the maf is unknown, i'd change it regardless
Would a knock sensor cause cause these symptoms????

MattyB1983

iTrader: (51)

Have you tried doing a CEL check to see if any faults are stored ?

http://www.jollygreenmonster.com/error_codes.asp.htm

chocolate_o_brian

iTrader: (22)

I had dodgy knock sensor wiring and the CEL would kick in for a bit, resort to limpmode and then be fine. I don't remember the car stalling but it did idle funny until sorted.

ad uk

iTrader: (6)

I've got a mad for u pretty cheap pm me

ad uk

iTrader: (6)

And I'm from walsall

MattyB1983

iTrader: (51)

If your gonna put a MAF on it then please do yourself a favour and buy a new one. Pointless spending money on a second hand unit.

ALi-B

iTrader: (1)

Point to note: If he's done the fabled and useless "unplug the MAF test" it WILL have logged a fault code because its been previously unplugged.

+1 I can't belive how many people try second hand units or go for non-genuine ones....you cannot test the accuracy of a MAF sensor. They gradually degrade with age and the copies aren't always brilliant ( I had a ding dong with Fuel parts over this after being supplied with several faulty units ).

The crux is in 95% of cases the MAF generally works, but its accuracy is impaired. Typically they underead at high rpms (and high boost) and become less senstive to small changes in airflow at lower engine speeds (and low boost) causing hesitance and a feeling of the car "holding back" under light/mild aceleration, also typical symtoms is difficulty to maintain a steady fast idle (especially on cars with electronic throttles); Say hold it at 2000rpm with a fixed position on the pedal (with a fully warmed up and hot engine), if the revs keep rising and falling without moving the pedal, the ECU is having a issue maintaining the AFR as the oxygen sensor readings are fluctuating (which causes the revs to changes as it changes the fuel trim).


HOWEVER, I've said it once and I'll say it again; CHECK for leaks on the intake system first before randomly swapping parts, no matter how small it will cause running problems. even a leaky dumpvalve diaphragm or the small hose going to it will cause "MAF-like" symptoms. (As the MAF can't detect leaking air so gives inaccurate readings).

MattyB1983

iTrader: (51)

What about if he resets the ECU first, then goes for a drive.
All previous faults would of been wiped and only new faults should come up on the test.

matt077

iTrader: (2)

well i had the problem of the apexi reporting a silly number of knocks which truned out to be a few lose bolts around it tapping the senor (lol)

My new MAF as turned up today so hope to fit it and see if this fixes my problem

would i need to reset the ecu (green and black wires under dash) after i fitted this? (i'm running a apexi ecu too)

i did find a jubilee clip from the maf hosing to the intake hose was lose so i've fixxed that now too

neilwrx

iTrader: (7)

yes reset the ecu and to do this just disconnect the battery for 15 mins and give the iacv and good clean to this can also cause stalling if it sticks