Baggers

Odd problem with my standard uk MY99, I've recently changed the MAF and Lambda due to MOT emissions problems. Seem to have developed another problem now, I'm getting very severe on / off hesitation when on hard throttle and on boost from about 3.5k up to about 5k rpm, the problem then clears and she takes off like a scalded cat.

• If it were a coil pack / HT lead / plug related, would this problem clear at 5k rpm? Don't think so, I'd imagine it to be worse at high rpm.

• Could be the boost solenoid but have squirted brake cleaner into the hoses at the T piece a couple of weeks back. Do these 3 port soleniods exhibit this problem?

Any help / advice appreciated!!!

jjones

unlikely to be ignition as the harder the system is worked (higher loads) the worse they tend to get.

when you cleaned the boost solenoid did you connect the green connectors under the dash board?


how severe is the hesitation - head through windscreen (could be fuel cut) or minor "missing" (could be a plug).

Baggers

No, I didn't connect the test cycle connectors previously, but I've found a good thread on how to clean it properly and will be doing so this weekend.

The hesitation is certainly enough to jiggle you about gently in the drivers seat and spill coffee all over yourself but not enough to give you windscreen related brain damage. If it was plug / fuel related I'd be surpsrised as fom 5k > she's fine.

Scooby Skunk

I have the same problem with my98 i put it down to overfueling on acceleration think i might go and have it checked now.

FB Tuning

iTrader: (30)

How recently did you replace MAF and lambda?

Did you reset the ECU afterwards?

Baggers

Yes, ECU reset after replacing the MAF and Lambda. Also subsequently checked for errors. The problem was apparent almost straight away after replacement and reset. I thought it may be the ECU relearning but surely not after 100 miles of varied driving?!?!

chrisp

what fuel are you using, nul or sul ?

Baggers

Always Optimax.

chrisp

have you got a boost gauge, if so what are you getting peak boost. Just wondering if you are hit overboost/fuel cut

Baggers

Gauge is on order, it's a possibility. What would the root cause to this be though?

Steve Cranfield

iTrader: (2)

If you have a full decat system it is prob because of over boosting, had the same problem with mine, on full throttle it was ok till abot 3.5k, then was like hitting a wall, sudden loss of power, then it would go back to normal!

I fixed the problem with a dawes device to hold the boost at a certain level to stop the overboosting happening. This was fine, but now i have a remap so no need for it.

hope that helps a bit, i'm not the best with technical bits!

chrisp

full decat can raise boost levels and allow the boost to come in earlier mix in cold weather and this could cause overboost.

Does this only happen if you are on full throttle or does it happen on partial throttle.

Baggers

The car's standard, all cats present and correct. Seems to happen on anything from 2/3rds throttle on, possibly pointing the finger at a boost level related problem? I'll give the solenoid a good once over and all the surrounding pipework a clean through. If that doesn't solve the problem I'm a bit stumped.

Baggers

BTTT anybody else had a similar problem?

kilo_4que

I had exact same problem and after changing spark plugs etc it still remaind. Was cured by a new Air Flow sensor cost 77 quid from dealer

Baggers

Isn't that the MAF? Changed that for a new part - no change

Dave uk blue mica

no its not the maf mate, thats the sensor i changed on my scooby too and it cured it, my maf was fine

kilo_4que

yup, hes right

Baggers

Interesting, where do I find the air flow sensor?

Trucker Ted

MAF is the Mass Air Flow sensor? Only sensor on the air intake side or so i thought??

Baggers

doh, can anybody clarify this 100% and actually tell me where it is? cheers

RON

under the bonnet theres the airfilter housing on the left front, then there's a lump with wires coming from it, and then a flexi pipe, the maf is the bit with the wires!!

Baggers

Understand that, I've changed the MAF, I'm trying to find out whether there is really another seperate "Air Flow Sensor" part, don't believe so, I think they're one and the same. The MAF is the only air flow sensor on the intake system, or so I though up until about 20 mins ago.

kilo_4que

the thing is matey that initially someone told me to change the MAF too and the guy at subaru told me that it would be a waste of money, rather just buy an air flow sensor. The air flow sensor is like a plastic fuse thing roughly 2 inches long with a wider flat end which basically slots into the MAF as far as i know, or wahtever u call it on the air intake. it slots in n u tighten it.

maybe the MAF u bought already had one on but they are very weak that with a little too much movement the thin wire inside can snap. Its a different case once its installed on the car though

RON

The MAF is the sensor, the bit it bolts into is the sensor body!!!

Baggers

Agreed RON, have spoken with the dealer, they suspect a dodgy new MAF!!!!! Will be going in tomorrow to swap it out with the boys in the delaership garage, see if that makes a difference. They said that my symptoms were classic MAF failure.

Gawley NI

Let us know if this works because im having exactly the same problem as you are on a MY00. I have only added a magnex rear box to the car, apart from that its standard

ScoobyDoo555

From what you've said, I still think it's a MAF mate - they're the weakest part of the 99/00 engine

Like I said, mine got damaged by the mechanic just changing a dirty air filter @ service. A spec of dust can **** it totally.....

For £80 it's a cheaper option than the entire MAF (about £250!!)

Hope you get it sorted.

Dan

kilo_4que

see i knew i was right. The sensor is not the MAF itself is it scoobydoo?

cos the dealer told me that the MAF is the whole thing and what needs changing is the Air flow sensor that slots in it. and yes they are very delicate, a little nock and that wire thing inside rips

Baggers

Still, wouldn't expect a brand new MAF to be screwed out of the box, time will tell!