BlkKnight

scenario:

I'm out for a "hard" drive & am booting it in all gears. I get to 4th gear and @ 5000 RPM the engine "stalls" for want of a better expression for 1/2 a second and picks up again.

It's reproduceable.

Only in 4th

Any suggestions?
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'97 sti wagon
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BlkKnight

more info

been running on optimax for about 4 tank fulls

Car is "vanilla"

chrome

search for MAF threads mate... its a good starting point.
possbily fuel cut? unlikely tho if car is standard..

BlkKnight

OK, I'll do the MAF test's tomorrow. & see how it goes.

mikey f

Overboost is also worth a search. I had this on my MY98 uk car. The Boost is over-read and as a precaution the fueling is cut. It feels like when you over-rev a diesel and the fueling cuts out - loss of power suddently but returns almost immedietly. Can't remember what got cleaned and re-lubricated but ask on here..
Mike

The_Judge

When it occurs, would you say it's a hesitation or "hit brick wall" moment? You might need to do some or all of the following:-

- Do the MAF tests.

- Check there aren't any splits in any of the vac hoses, from the compressor to the wastegate solenoid, and wastegate actuator.

- Check the restrictor before the T-piece isn't clogged with dirt.

- Clean the wastegate solenoid.

- Make sure the wastegate actuator arm is opening the wastegate sufficiently.

BlkKnight

after speaking to the mech who just serviced it, he said the pipe from the manufould to the boost sensor was disconnected - and therefor the ECU didn't cut off fuel when overboosting.

After connecting it the ECU now corrects overboost. The question is why is it overboosting???

My gut feeling is that the chap who owned the car prior to me had "tweaked" the turbo somehow to up the PSI.

I'd like to put it back to standard - as it's plenty fast enough for me (at the moment).

Suggestions?

J

JohnRoly

Had a similar problem, first changed the boost solenoid, then the restrictor - it turned out to be a leaking wastegate actuator. Try disconnecting the actuator from the solenoid and see if you can suck & blow through it - if so, it is leaking and needs replacing!!

Hope this helps!

BlkKnight

Thanks for your help guys. I'm popping it back to garage tonight to see how it goes.

J

The_Judge

There might be some sort of manual boost controller or bleed valve in operation. Especially if the previous owner disabled the fuel cut...

Get them to initiate ECU diagnostics mode, and clean the wastegate solenoid with brake cleaner (or equivalent). Also give the T-piece a good squirt, and check the restrictor isn't blocked.

You might be able to slacken off the wastegate actuator arm if the wastegate is one of the problems...