I have a standard MY96 (with S/S backbox), in the past 2 months (S/S put on a month back, no change) I've been getting an overboost type cut out, like a small misfire. Not a head against windscreen type cut, but drop in power at approx 5500 revs.
Garage has replaced all firing units, with no effect.

Upon checking boost the car is peaking at a constant 1 bar (3rd gear), with a constant .95 bar in 1st gear. What is the correct boost for a UK ?, and when would the MY96 UK ECU cut in for overboost.

If anybody has any suggestions for the cause and cure, please let me know. I'm supposed to be putting it on the rolling road on Sunday at Well Lane.

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Thanks.

Darren.

Are you running the standard air filter?

Yep, standard filter put in at last service, last month.

Darren.

In fact standard everything except the back box, but I had the problem before I fitted the back box.

Darren.

Just tried to post a long one but it disappeared - so this is much shorter.

I have had a similar problem on an sti5. Result of thrashing on inferior fuel (e.g ron 95) - ecu cuts in and cuts out boost, at around 5500 - like a light rev limiter - not harsh - but annoying - went back to Super and no problems - conclusion crap fuel - have you tried super, i.e. do you get the same result? - could try everything except Esso (or JET for that matter) - as these are the Garages I have fuel problems with!

Re Exhuast/filter - allows slightly higher max boosting as the engine revs fre - er. As for 1 bar boost settling to 0.95 bar - sounds a bit high for a uk car - would expect nearer 0.85-0.9 bar of boost - but then every car seems different - 1 bar is not overly high as the UK ones can withstand up to about 1.2/1.3 bar - the one at 21psi is stupid and I'm surprised the engine has not blown - you know the one.

Mine is running at 1.5 bar overboost -settling to 1.35 (but then its got a Possum now).

One way of stopping overboost is to fit a 3 port boost solenoid - has your car got 2or 3 ports on it? (-the thing in front of the drivers side top suspension mount) - I had bad overboost until I scrapped the 2 port and fitted the 3 port - takes 5 mins and costs £100 all in

Steve

The last two tanks have had normal in, with the tank before that super. Seemed better with the tank of super, but it was still there. Reset the ECU (plug method), as well after filling up.

Could try that, have to wait a week, just filled up with 95ron.

Anybody got any other suggestions, for things to check ???

Darren.

This may not be much help but you could always get a rolling road check done at Well Lane - they may be able to identify the problem -if it occurs on the rollers?!

Tried regapping the plugs to 0.6mm, because of suspected spark blow out, no different.

Has anybody got any suggestions.

Do you really think the 3 port soleniod would fix the problem ?? £100 plus fitting is a lot if it doesn't work.

Please help .....

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Darren

Darren, you already have a three port solenoid on a MY96.

I'll mail you alist of things to check, trouble is it could any or all of them.

Bob

Been back to the garage again, tried a new blow off valve, and a new boost pack (inc. MAF sensor), with no change.

Moving on now to faulty actuator ?

With the car running 1bar boost, does anybody know if the fuel pump would beable to keep up supply.

Fuel Pressure Rail ???? possible supply problem ???

Any suggestions...

Darren.

Of course it would - it can handle a hell of a lot more than that!