Peanuts

iTrader: (15)

coming to a junction and/or stop, the revs fall to below 750 and then bounce back up to about 900 before settling around 750.
symptomatic of:
maf?
Lambda/o2?
anything else?

Also, I think Ive over filled the gearbox oil, what damage can I cause?
is it worth my getting a select monitor plugged in?
does anyone outside the Subaru franchise own one?
your thoughts please because the diagnostic is showing no error but the idle was steady as a rock before.
Andy

running full decat (turbo back) and green cotton filter, knock sensor, AFR (not yet wired in) meter and boost gauge.
maybe have lost 0.05bar of boost but not 100%sure.

STi wanna Subaru

iTrader: (1)

I've heard it is a sign of a failing MAF sensor. Try a search on MAF and idle

Pete Croney

Andy

If the car is a 99/00, then a fluctuating idle is the classic indication of MAF sensor failure.

If the car is earlier, its probably a sticking idle speed control valve.

Peanuts

iTrader: (15)

Thanks guys, that was my first thought,
so I changed it with another member on a meet last month (albeit for their second hand one) and no change in the situation....?
Is there an alternative to subaru MAF if they are that pants?

Pete Croney

Peanuts

As the ECU compensates for a certain amount of deterioration, changing it with one from another car may not disprove it. The one you changed it for could also be at less than optimum health but the ECU on that car is coping with it.

No other part options are available.

Abbylad

iTrader: (4)

I`m having same problem, whats supposed to happen if you whip the plug on the MAF out while the engine is running? if i do it on mine it stalls immediately, think i remember seeing a thread saying that this is what should happen, and that if the engine doesn`t miss a beat and keeps running then the MAF is fcuked, or was it the other way round? can anyone throw some light on the situation please

Peanuts

iTrader: (15)

Pete,
another symptom I noticed tonight was that there is about 1/4" of soot around the inside of the tailpipe.
running excessively rich?
Andy

ps, have taken your advice and ordered a new MAF anyway

Peanuts

iTrader: (15)

Pete,
just while I have your attention.
Do you know if the Samco hose kit for MY97 car will fit a MY99 car?
Andy

mack

iTrader: (1)

hi
I kind off have someting like that in my car at the min.
If yer coming to a roundabout or similar where you have yer feet on the brake and the clutch and when the revs drop the needle hits rock bottom and then idles fairly ok, I really notice this when the car is warm, Sometimes ie 4/5 times in the last 2 weeks the car has actually cut out.
I have enquired about this and it turns out that the guy that had the car before me put in a single piston dump valve along with the OEM dumpvalve,( both are running). Im told that the single piston is leaking back air to the manifold and it's that affecting my idle speed.
I'll be putting on a proper forge dumpvalve before the weekend, I'll keep ya posted

Hope it's some way helpfull
rgds
Mack

greasemonkey

Moot point, as disconnecting the sensor when the engine is running is not a particularly good idea, and you don't learn anything useful if you try it.

If you read in an SN thread that driving your car off a cliff would improve its acceleration, would you try it?

This test doesn't prove anything, and could concievably damage the ECU. You need to find out if your sensor is 100% functional, or unacceptably degraded/failing, and this "test" simply can't tell that difference.

The only thing it can diagnose is a sensor which has failed open circuit. They very rarely fail like this, and even if yours had, you wouldn't need to disconnect it to find out, as you would be getting a CEL...

ozzy

So how do you check to see if the MAF has failed or is failing? without shelling out £80 for the pleasure of "testing".

Stefan

greasemonkey

It's difficult to avoid gettig another sensor. Borrowing a new, or known good one from a dealer or friend may save you having to shell for one.

DeltaDash, Select Monitor and SECS can indirectly tell whether the sensor is misreading, but you'd really have to know what "normal" readings were before you could tell whether yours were abnormal, so still really need another sensor for comparison.

Abbylad

iTrader: (4)

Apologies for following someone`s advice GM! please allow me some time to go find someone to nail me to a cross!!!!!!!!