PeterStone

iTrader: (1)

I'm currently suffering from hesitation between 2000-3000rpm on a MY99 with TEK3 remap.I've checked plugs , cleaned out the boost solenoid , checked all turbo piping so am now looking at the MAF sensor.I believe if you disconnect it while the car is idling and it stalls then the sensor is knacked.I did this and it still ran all be it unevenly.However when i plugged it back in the engine then stalled-is this right or what does it mean?

I have an AFR gauge which seems to be reading normally and boost is peaking at 17/18 psi.It's just the part throttle response that seems lumpy to me.

PeterStone

iTrader: (1)

Anyone?

Just want to know if the car stalling when i reconnect the maf is correct or not.

PeteS

The_Judge

It's the other way round mate. If the engine stalls when disconnecting the MAF, it could indicate that the MAF is OK. If there is little or no change to the idle, then it could indicate that the MAF is failing. It's not an exact science though.

The other MAF test is to reset the ECU. If the car drives considerably worse and idles worse than before the reset, then that's a much stronger indication of a failing MAF.

If it's part throttle response that's playing up, it could be your lambda sensor. Do you know when it was changed last? They're only about £25 from any local motor factor.

Have you got a Knocklink? Any unusual activity?

What plugs are you using?

PeterStone

iTrader: (1)

Lamda sensor changed about a year ago.

I have got a knocklink but only ever see greens.

The plugs are NGK PFR6B gapped at 0.7mm

MAF replaced 2 years ago.

PeterStone

iTrader: (1)

Anyone?

The_Judge

PFR7Bs might help a little, especially at that boost level.

Have you tried resetting the ECU yet...?

PeterStone

iTrader: (1)

Have just reset the ECU - no fault codes present and it does seem to run a bit better but there's still the lumpiness between 2000-3000rpm.It's not hesitation as much as the power comes in stages almost - not linear if that makes sense.

Pete

PeterStone

iTrader: (1)

Judge?

The_Judge

Sorry mate I'm a bit stumped really. The resetting of the ECU seems to have proven the MAF is OK. If the MAF was knackered, the idle would be all over the place, and it would drive like a bunch of **** whilst the ECU started to learn its way round the failing MAF again...

Does the boost gauge correlate to the surges, or does it stay at 17/18psi throughout?

It could still be your lambda, even though you replaced it a year ago. A test for that is to simply unplug it. Drive around and see if it's any better or not. Actually, that's a point. When you reset the ECU, did it reset within a few seconds of driving, or a few minutes...?

PeterStone

iTrader: (1)

Thanks anyway:-)

It's really only while driving at part throttle , about 2000-3000 rpm so boost is only just starting to build so assume it's not boost related.Once beyond 3000 rpm it is fine and holds 17-18 psi.

The CEL light came on within 30 secs or so.

Will try unplugging the lamda sensor to see what difference that makes.

Cheers

PeteS

PeterStone

iTrader: (1)

Do you have to unscrew the whole lambda sensor from the downpipe or do the wires plug into the sensor?
If you have to unscrew the whole thing is it best to remove the intercooler first?
It seems to be at leat 20mm across so what tool is best as can't get spanner/wrench in.Do you need one of those stubbie spanners?

PeteS

The_Judge

You don't need to remove the whole thing. If you follow the wires from the back of the sensor (not far, few inches at the most), they should end in a small connector, which is connected to the wires from the main loom that goes to the ECU. Simply disconnect it.

The_Judge

Incidentally, if you ever need to replace your lambda, it's easier to get at from underneath... unless you've got tiny double-jointed arms/wrists

PeterStone

iTrader: (1)

Having disconnected the above the car accelerates a lot more smoothly and feels quicker.The AFR meter no longer moves but i assume this is because it takes the signal from the O2 sensor to calculate the AFR.

This was a Bosch universal sensor fitted less than a year ago so do i go Bosch again and hope it lasts longer second time around or go for the Halfords cheapie and treat it as a consumable item or pay up and go for the official Subaru item in the belief that it will last longer?

PeterStone

iTrader: (1)

Anyone?

The_Judge

You're correct regarding why the AFR gauge has stopped working.

Do you use octane booster? It's a possible reason why your present sensor only lasted 12 months. I think too rich a mixture can also lead to a low lifespan. Or it could just have been a bad one...

I think the Subaru OEM sensor is more than £100, so assuming you're paying £25-£30 for the universal, I'd personally stick with that. Would the OEM last 4 years or more? Unlikely, so you might as well use the universal and change it every year. Same cost (more or less) and you have the benefit of knowing you have a brand new sensor every year...

PeterStone

iTrader: (1)

Thanks for the reply.

No i don't use any octane boosters.

The current sensor is a Bosch one that TSL fitted and was £90-ish.

The_Judge

£90...? Ouch. Give the Halfords one a go, or do what I did. Use www.yell.com to find your nearest Motor Factor. Should be about £25...