I've did a search to see if my problem has been covered but can't find anything identical, although there are plenty of similar threads....

My MY99 UK Turbo has been idling a wee bit unevenly recently so I have a new MAF on order to try and rectify this.

Yesterday I fitted a full de-cat to the car and the following problem has manifested itself.....

Firstly, the car does not have a boost gauge or AFR fitted yet, so my description of the symptoms may be a tad inaccurate due to this.

When on full boost the car pulls like it should, however, when it hits 3-4k rpm, the car lags ever so slightly, before coming on song again and pulling all the way to the redline.

The "lag" that I describe is not a violent lurch like some have described, so I assume it isn't fuel cut.

Could the car be overboosting at low revs due to the de-cat and/or MAF?

Why does it correct itself after its slight hesitation?

Is there anything else I should be checking?

The car is running a bog standard MY99 ECU on SUL and as far as I aware, this hesitancy did not occur prior de-cat.

Any ideas/suggestions?

Would an ECU reset be a good idea given the recent de-cat.

Can anyone point me to a thread describing the ECU reset procedure (using the black/green plugs) as I can't find one.....

Cheers

 

Don't bother resetting the ECU. An empirical MAF swap is a good idea anyway if anything is amiss at this age.

It is probably overshooting the boost target slightly due to the decat.

Drive gently until new MAF and boost gauge and tell us what it shows.

 

Cheers John, I kinda thought you'd reply!

 

Mine has does this in the past and it's been the boost solenoid.

 

hi mate,
mine also has this problem.also a bit of surging,more noticable at about 3000rpm. bought some brake cleaner today gonna clean my boost solenoid tommorrow. mine is my99 uk turbo, full de-cat,green panel, samco hoses.

Lee

 

Checked it again tonight..... car pulls fine till about 3200rpm, then it hesitates till about just under 4k rpm where it pulls again.....

I'll fit the new MAF when I get it and clean out the Boost solenoid and see if it rectifies the problem.

 

I know it a long shot, but you haven't got a ****ty AE802 ECU fitted to your car by any chance have you? I had what sound like similiar dramas on my MY 00 for ages, and changed the ECU for a AE801, the difference was amazing. Then Dr Banks did me a remap (on a spare AE802 ECU) and I haven't looked back since

Thanks Phill

 

does it fell more like a gentle mis-fire rather than a power loss?

if so http://bbs.scoobynet.co.uk/showthrea...ght=stuttering could be of interest to you.

 

babber,

Don't think it's the ECU, but I was planning on a swap for a TEK3 at some point anyway, so I'll do the other things first and see if they solve it.

jjones,

Interesting read, and your symptoms sound very similar, although I wouldn't describe it as a "stutter" as this implies some sort of jerky surge..... its more "hesitant" so much so, that passengers may not even notice the slight hesitancy... thats how smooth it is.

I'm night shift all week, so won't get much opportunity to address the items, but as soon as I do, I'll post up the problem.

 

Have you checked the ECU though ?

Around this sort of RPM I thought the AE802 ECU maps were modified to give better fuel emmissions or something, but I had a hesitation on my MY 00 and after changing the ECU (for a AE801) the car was a flying machine.

Just a thought.

Phill

 

its over boosting. had exactly the same problem with mine. the tiny restrictor in the boost pipe was changed and it fixed it

 

Disagree mate, over-boost will almost throw you through the windscreen, not hesitate a little. Sorry to disagree mate, but I really don't think a restrictor (or orifice) will resolve this issue mate.

Thanks Phill

 

It seems that there may be a multitude of things possibly wrong, so it's booked into main dealers next Tuesday so it'll just need to be nursed for a week.

Wahay! Decent fuel consumption ahoy!!!!

 

The car went in to the main dealers today for a diagnosis.....

They said that the oil level was a bit high, causing the boost and vacuum pipes to be full of oil, and subsequently the boost solenoid to be contaminated also.

They cleaned out the boost solenoid and re-set the ECU which showed fault codes for the MAF and lambda sensor. He also said that this wasn;t completely reliable and that he supspected MAF failure, but not lambda and put the lambda fault code down to the dodgy readings being sent by the fcuked MAF.

As a result of the solenoid being cleaned and ECU re-set the car is running a bit better but still not perfect so it is going in next Monday for an oil change to get the correct amount if the right oil in it, and back onto the diagnostics machine and then a new MAF to see if it cures the problems.

I'll keep you posted if it doesn't go bang in the meantime!

 

Progress at least John!

 

Don't drive it on full throttle if the ECU picked up a MAF code. A reset could make it **** itself combined with caning it. Drive it off boost until the MAF is changed.

 

Yes, and you were right about the solenoid Carl!



No problem.
Prior to ECU re-set the car was idling slightly unevenly, but now its hunting like a bugger!
In fact I stalled it twice on the way home form the garage! Mucho heel-toe required!

 

mine done exactly this straight after it was de-catted. It was over boosting and there was a slight hesitation and drop of power while the ecu brought the boost level down. I do have a boost gauge and could see this happening. A Remap cured the problem and i now have a nice stable boost level.

 

Got the car back last night and they have drained the oil from the sump, topped it to the correct level, cleaned out the boost pipes and solenoid, and fitted the new MAF.

The car now idles perfectly and does not hunt whatsoever, however there is still a very slight hesitation between 3 and 4k rpm.....

I'm wondering if a re-map/new ECU would recify this after the recent de-cat?

I have posted a wanted ad for a PPP or TEK3 ECU.....

thoughts?

 

A bit of advice if you'd be so kind.....

As per last update, the car is still not quite right after the work that has been carried out.

Would my next step be to replace the spark plugs, or look at a remap?

Would fitting a bolt-on PPP ecu be of benefit, and eliminate the boost flat spot?

Thanks

 

Do yourself a favour and check the ECU in the passenger footwell to see what ECU you have..

A remapped ECU will eliminate the hesitation IMHO, if you have a AE802 (green labelled) ECU...

Phill

 

They all hesitate slightly when running closed loop when cold. When hot, if running to spec, even an AE802 shouldn't hesitate, it will be slow, but shouldn't hesitate. An ECU map will probably help with performance.

 

Since you are no longer operating John, who would you receommend in the central area to remap my ECU?

 

Does Andy Forrest do EcuTek remaps or just the Apexi stuff?

 

He does both, and I would recommend him.

 

I've pm'd Andy, so watch this space!

 

Car will be going for a remap with Andy.F very soon hopefully!

 

I have a set of new spark plugs on order from Alyn at AS Performance (NGK PFR7B's) and have contacted Andy.F about getting me booked in next week for the remap!

 

I don't mean to hijack this thread, but this sounds a little like the problem I've been experiencing (MY99 full decat).

Accelerating hard to full boost (i.e. flooring it), I sometimes get a stutter, hesitation, there's also a slight noise, like a bubbling noise. Knocklink doesn't go above green though.

The problem has only started to make an appearance since I replaced the battery, thus triggering an ECU reset.

I think this may also be an overboost problem, although I'm not too sure where the sound is coming from, I think it may be the turbo/wastegate?

Best course of action? Clean the boost solenoid? (where ever that is)

 

I'm sure someone will post a link on how to do it. I think the boost solenoid is on the drivers side, top of the wing. It's brown with a copule of pipes attached to it.

Thanks Phill