Robocop

I have a 6 month old MY04 STi with PPP fitted. The car has done just under 6k and I'm getting a misfire in 2nd gear at around 6300rpm.

It happened about 3 times tonight on the way back from the Dorset meet and so far it only happens at roundabouts, when the load on the engine is at its maximum I guess.

Approaching a roundabout fairly quickly, come done the gears to 2nd, off boost until I reach the exist and then apply full power. The engine hesitates for a second, a bit like a rev limiter cutting in, a few pops and I immediately change to 3rd.

It ONLY runs Optimax and was just under 1/2 tank of fuel.

It happened last week but I was low on fuel then, so I thought it was a fuel surge problem.

Any ideas before I call my dealer tomorrow?

Robocop

The dealer thinks it's over boosting and it's booked in for this Friday to have a check up.
Is there as reason why it doing this?

MikeWood

Put some more fuel in it, it's still fuel surging! It'll probably have taken some ignition out as well now as it thinks it's seeing det at 6000rpm so it may be a good idea to reset the ECU to remove the negative correction.

Mike

Robocop

I'm only guessing it's fuel surge, but having spoken to my dealer (the excellent TH White in Cirencester), they have described it as sounding like over boost.
I'm not for one minute doubting your word Mike, but let's just say that is the problem, why is it happening?
BTW, I've had a set of Defi's fitted 10 days ago and max boost shows at 1.4bar
Regards
Kevin

MikeWood

1.4bar is fine as it'll only be happening for a very short period of time. It's very doubtful that you would get overboost in second gear, it's much more likely to happen in the higher gears. An overboost would also put on the CEL.

Mike

Robocop

Mike

No CEL coming on.
It's only happened in 2nd gear,as I don't push it too hard in 1st because of the sheer strain it puts on the drivetrain etc.
From a standing start, going easy in 1st and then hard from 2nd onwards the problem doesn't happened. It always involves a roundabout. I would say there was around 20-25 litres of fuel (Optimax) last night.
Where is the fuel pickup in the tank BTW i.e front left centre rear etc?
Anyway, your input is very much appreciated.

Kind regards
Kevin

ShyTot

I agree with Mike, my MY02 STI will do this with up to 1/2 tank of fuel if you push it really hard on the roundabout (right hand turns)

MikeWood

The fuel pickup is in the rh side of the tank so driving round a roundabout will put all the fuel on the lh side of the tank so when you need it, there's no fuel there.

Mike

Robocop

I'll fill it tonight and try it.
Have you come across this before Mike and is it still advisable to have the ECU reset?

Thanks
Kevin

Robocop

Well I went to my local dealer on Friday.
I had 3/8 of a tank of fuel.
They connected the Select Monitor and I drove them up the road to replicate the problem.
Sure enough it happened at exactly the same point. They recorded it on the monitor, but as yet, they're a bit stumped on the reason why it occurring.
Has anyone any suggestions?

Dark

iTrader: (1)

Still sounds like fuel surge.

I've seen MY02 STI's have the same problem around the hairpin (right) at Knockhill with >1/2 tank of fuel.

If it was overboosting you should be able to replicate the fault whilst driving in a straight line, it wouldn't only happen going around corners.

Mark

Robocop

Thanks Mark for the info.
Mike, have you come across this during testing?

Gridlock Mikey

Not sure if it affects later cars, but could it be that emmissions patch they programmed into the ecu to pass drive by and emmissions regulations over here?

I know my car used to do it if I held the throttle at say qtr or half and then floored it, even in a straight line. I used to experience it most though exiting roundabouts. Not sure where the fuel pickup point is on a classic, but i used to come round the island, set the car up onto the exit i needed (Essentially getting the car to settle onto it's right hand suspension) and if i just nailed it, i'd get this lack of power, like the car wanted to boost but was being prevented. If i took my foot off the accelerator or depressed the clutch quickly and then booted it, it was fine.
(Don't do the clutch/lift off throttle thing when it's wet or the car is not settled )
Just a thought, not even sure if the new scoobs even needed an ECU cheat to pass some tests

MikeWood

Yes, it's fuel surge and I've experienced it with over 1/2 a tank of fuel on our track whilst testing. Does it do the same thing when it's full?

Mike

Robocop

Hi Mike
I haven't yet tried it with a full tank of fuel, only just under half. I will fill it up and retry it.
If all is then OK, would you suggest an ECU reset, or would this be a waste of time?
There were no faults logged in the Select Monitor, but I'm a bit of an anorak as far as my STi is concerned Aren't we all?

Dark

iTrader: (1)

If it's fuel surge then resetting the ECU should have absolutely no effect.

In fact it could do more harm than good since the ECU will loose all the data it's collected regarding ignition timing, etc and will default back to the standard "safe" settings.

You could find that performance is temporarily lost as a result !!!

Mark

Robocop

Many thanks for all the advice.
I'll fill up tonight and leave the ECU well alone

Regards
Kevin

MikeWood

Yes, a reset may well be in order as there's a good chance that the ECU has learnt that at 6000 rpm it needs to pull ignition timing out. This will be because there may well have been occasions when it didn't quite cut out but did run lean and some det was experienced. The ignition correction table may well have some negatives in this area which the ECU can't take out as it can't spend long enough in that load site to be able to try more advance. You'll be able to tell if you try a 3rd gear pull (in a straight line) and if you feel a small step in the power delivery around 55-6500 rpm then it needs a reset.

Mike

Robocop

Mike,
Thanks for the quick reply.
A full tank of Optimax, a visit to my local Subaru dealer for a ECU reset and a fun trip back home, is the plan of action for tomorrow

Regards
Kevin