Ian Waller

Starting yesterday my STi II started (this is the only way I can think to describe this) violently hesitating. It started last night when I was accelerating away from a roundabout onto a dual carriageway from 3rd to 4th, at about 5000rpm, the car was pulling HARD, then it stopped pulling (violently), almost like I had stamped in the brakes for a second, then continued on again???!!!! The car then did this again several more times last night.

My observations so far:
- I have a K&N induction kit, this means that I can hear the standard dump valve. Unlike when you liftoff mid hard revs, when the car is hesitating, the dump valve does not go off.
- When the car hestitates, the revs do not drop.
- I filled up yesterday with my second tank of Optimax (although different garage to the first tank).
- The hesitation can happen at any revs, but is more violent higher up the rev band.
- The check engine light does NOT come on.

Please help, as I am sure you can appreciate, I am very worried about this.

Ian.
STi II

chuckster

Overboost cut? If you used to run on SUL 97 octane Optimax's claimed 98.4, coupled with colder weather and your Induction kit, could be causing overboost. The ecu compensates by cutting boost momentarily hence the 'violent hesitation'. You could try going back to the standard airbox to see if it helps. If this is the case there are ways around it.
Chuck

DavidBrown

It's cutting out to prevent the engine going *POP* due to overboosting.

Sound like a wastegate solenoid/actuator problem. Either needs replacing/cleaning.

Common when engine is overfilled with oil (engine service recently?)

Dealer can fix it in 10 mins.

When it first happens, it's very unnerving.

Josh L

Sounds like the problem I had on my MY98, and description fits that of other victims as well.

I beleive it was described as a 'boost pressure sensor' problem. They took all of about 3 minutes to replace the unit....no more problem.

Josh

JackClark

Same problem/solution on my MY98. That's some scary s*it though!!

john banks

Put a boost gauge on.

Ian Waller

Had the car serviced about 8 weeks ago. The garage specifically overfilled with oil (stating that this helped to protect the no.3 piston).

Driving the car this morning, it is not doing it. Is this one of those intermittent things, or if it is overboost, should it not be doing it all the time?

One other point to note is that I am (but just as I have always done) running millars octane boost as well.

Ian.
STi II

beaker

Ian,

I had exactly the same problem with my STi2 when i had it . The problem was finally fixed as stated above..

"Sound like a wastegate solenoid/actuator problem. Either needs replacing/cleaning.

Common when engine is overfilled with oil (engine service recently?)"

Oil had began to get into the wastegate solenoid/actuator, causing it to think that it was overboosting. Once it was cleaned, it didn't hesitate anymore (not for about 4 months anyway.)

Craig.

SCOOP

Hi Ian,
Sounds symptomatic of dirty a Turbo Solenoid to me.
Both the solenoid and the narrow rubber pipe tend to build up an oil residue, especially if you fractionally overfill the sump with oil.

I experienced exactly the same problem and after cleaning both with brake cleaner (don`t know if this is the best thing, but it worked) the problem was cured.

Good Luck

SCOOP

Ian Waller

The car was playing up again yesterday. One thing that surprises me, is that it plays up at low revs as well. Would this be the case if it is a turbo problem?

Anyway the car is booked into Powerstation for next Tuesday. Now do I get the bumpsteer mod done as the car will already be there.