yhe chod

if a maff sensor fails and you continue to drive it on a long motorway run say,both on and off boost but not wot.
whats the worst thing that can happen to the engine.
i presume it would run very lean and would the ecu retard the timing to stop damage to engine??
what can be damaged without knowing it or being too obviouse

New_scooby_04

iTrader: (4)

It can kill your engine! Apparently one of two things happen, IIRC from talking to an expert 1) The car runs too lean and begins to det 2) The car overfuels to the extent that you get bore wash and then it's also potentially bye bye engine. The ECU can't always adapt, I don't recall why, but its something to do with the spurious signals being received from the dodgy MAF.

If you suspect a dodgy maf, drive off boost till you get it sorted.

NS04

pslewis

Fooookin Ell

Your Engine will be destroyed, hell will freeze over and Kylie will want my body!!

You'll get rough idling, bad running, CEL light maybe ................ you'll know its driving different!!

You CANNOT, I repeat CANNOT (unless you are a complete and utter dork) have your engine blow-up without some signals being sent LOUD and clear to the driver, if those signals are ignored ..... well ..........

Pete

Triple X

iTrader: (1)

You can have det without knowing, why do you think mappers wear det cans?! Det is an engine killer either from melting a piston or putting shock forces on bearings which could damage them!

New_scooby_04

iTrader: (4)

Ok, put it this way:

If uncle Pete is right and you take my advice and drive gently, you'll just feel a peeved that you can use your car's performance in the time it takes to get the maf sorted.

If I'm right and you take Uncle Pete's advice and drive as normal, on boost etc, then you may be looking at a bill for a rebuild!

Better safe than sorry! Why not ask the experts advice, for example Xtreme Scoobies: www.xtremescoobies.co.uk

NS04

madman_dan

I would definately go and see xtreme, they will do a quick engine diag, and will let you know whats wrong within 30 minutes.. ( and of course then fix it up for you )

i had issues with mine, which wernt the usual maf issues, but were wrong, went and had it sorted, was the maf in the end, now it's like a balistic missile again

Andy.F

You can I'm afraid Pete, here is what can actually happen.

In the majority of MAF failures, 99/00 UK and Sti5/6 in particular, the sensitivity of the sensor is reduced. This means low flow reads as not so low and high flow reads as not so high.
At low flow such as at idle, you MAY get a slightly uneven idle for a short period whilst the ECU automatically adjusts the closed loop fueling to match the revised airflow.
Anyone ever had the idle stumble slightly and then fix itself ? I know I have.

In the midrange flow area, all is well and you can go about normal cruise with no issues.

In the highrange (on boost) flow area, closed loop fuel control is deactivated and the ECU applies the fuel/ignition from the fixed maps. This is where the problems really begin.
The measured airflow from the failing MAF sensor is less than actual airflow so the ECU adds less fuel, in turn causing higher combustion temperatures. The car feels like it runs really well as the leaner mix is good for power !
The ignition timing applied is however more advanced than ideal as the ECU thinks the loading per cylinder is less.
At this point, one of two things can happen.
1 - The engine knocks (detonation) the knock sensor doesn't hear it and piston/big-end damage occurs fairly quickly. This detonation is normally inaudible inside the car, especially if it has an aftermarket exhaust.
Or -2 The engine knocks, the knock sensor hears it and the ECU retards the ignition timing, this causes a rise in exhaust gas temperature which in conjunction with the weak fuel mixture can cause overheating of the pistons. This in turn can either melt the piston crown causing piston failure or cause the piston to pick up (partially sieze) in the bore, overloading the big ends causing failure.

Option 2 gives absolutely no audible warning prior to failure.

Andy

yhe chod

so if the maff sensor is replaced with a new one. will there be damage or wear from the time it was driven [as mentioned at the start of thread] with a faulty maff.
ie car feels lacklustre and unresponsive low down now and the
exhaust is noisyer too?-kind of rough and boomy.
idle is ok
get flickers of reds[on knocklink] at idle sometimes??

would a diagnostic check at xtreme or powerengineering [which one is better??] show me if the piston rings are gone or would i have to do a compression check in each cylinder

yhe chod

anyone?

mushkinee

wen i start my car sometimes the revs drop like its gonna die and then go to idleing, also it dusent idle too well sometimes it is 2.0na.
where would i get this checked in gloucester could anyone tell me pls?
cheers

Houghton

iTrader: (1)

yhe chod
Think you ought to mention what MY you have and whether you've actually replaced the MAF, then someone can say whether the ecu should be reset or it'll sort itself.

Until you get some 'sound' advice, if you're getting reds on idle, don't run it but check everything under the bonnet is secure, hoses, vacuum/boost pipes, intercooler, anything and everything that could perish, split, crack, come adrift.

Laymans thoughts on K/l activity: mechanical knock in engine, split inlet pipe, 02 sensor, and of course MAF.

Both places you mention have good reputations, depends who's nearest to you. I'd wait till Monday and speak to them.


mushkinee:
Powerstation are near you. Good reputation.

yhe chod

yes .dho!!
uk99 ,new maf ,new lambda.[02 sensor]
reset ecu!

Houghton

iTrader: (1)

I'd be inclined to get on the phone Monday for advice on how to get the car to whichever specialist.

Good luck