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Discussion Starter · #1 ·
A problem that is gradually getting worse - sometimes when accelerating usually in third I get a sudden jolt which feels like I have just stabbed the brakes momentarily. Any ideas?? Doesn't do it all the time but when it does it probably happens a couple of times under medium acceleration. Haven't encountered it in any other gear yet.

9000 cse Eco lpt (94)

Any help appreciated as usual
 

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Its the car shutting down the fuel supply to protect its self, cured it on my 2.0 CSE 94 2.0 LPT by fitting new NGK sparkplugs to correct spec and gapped to 0.9mm, could by a couple of other items, others more knowledgeable will give you more details
 

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my aero did this, and although its not an LPT the following cured the issue:

1) New plugs
2) Change to optimax
3) Reset the APC and do a calibration run.

In you case as you have done the plugs and dont have an APC, it would be interesting to try Optimax and see if it makes a difference.
 

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Discussion Starter · #5 ·
I will give optimax a whirl to see how it goes - although the car has been fine through the acceleration range but for the last couple of months - I am leaning towards other problems perhaps!
 

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Discussion Starter · #8 ·
DI cartridge replaced 18 months ago and not much mileage done since - do they go often?

How do I check the wastegate? Forgive me for being thick but where the heck is it??!

Cheers for all the help so far
 

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Is it a really drastic thing, like you've hit a wall or slammed on the brakes? It does sound like the overboost cut-off switch. This could be due to a faulty sensor, or because you have too much boost, which is most likely down to the wastegate/actuator as Søren says. I would think you would notice an increase in power/acceleration before you hit the cut-off, compared to a normal LPT.

The wastegate is underneath the turbo. Have a look here for pictures. Check that the actuator rod is still connected to the wastegate, and that it is free to move a bit.

If you could borrow a boost gauge, that would tell you a lot!
 

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Discussion Starter · #10 ·
It did it twice last night at around the 3000rpm mark, and did feel a bit drastic to a constant worrier like me. It's a bit like slamming your brakes on suddenly for a brief second. I haven't noticed an increase in power but I will run it tomorrow to see if there is. Do you think that the rod could be sticking on occassions to cause the problem from time to time?
 

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My LPT sometimes stumbles... its the A/C kciking it.. but its not that big a jolt but noticeable at 70 mph.. (and my old 23. n/a use to stumble when you turned main beams on!)

Optimax doesnt seem to do much for LPTs.. or maybe I was just too stingy to pay an extra £3-4 a tank every 3 days.

I'd certainly give the wastegate a check out...does it only do it at 3000RPM?

Steve
 

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Try checking the small diameter pipe( about 12mm) that runs between the inlet/compressor side of the turbo and the wastegate. I had one with a little hole in it & enough pressurised air was escaping to prevent the wastegate from opening as early as it should.

This resulted in a bit of extra boost & therefore the over boost cut-out switch activated.

It's not very pleasant, particularly if you're overtaking something.
 

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At 3000 RPM´s in 3. gear is where the LPT´s are pulling full power as the the engine management system is limiting rews and tourgh in the lower gears. I belive you will experince the samt thing in 4. and 5. gear at full throttle witch I belive you havent done yet due to the speedlimits! So thats why the wastegate cuts off at that exact point.
 

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Discussion Starter · #14 ·
It's not like the A/C cutting in that's much less of a jolt and one that I'm used to! Looks as though I will have to put the car up on ramps this weekend to have a good look. It hasn't happened in fourth / fifth gear yet (although I have been fast enough for it to happen if it wanted), but I have found that if you gently push the acceleration after the jolt you can gradually ease in more power with no problems.

Happened the other night twice but I eased off the power and gradually over a mile or so increased the harshness of throttle and the problem didn't reappear - based on that would it be a leak in the pipe or perhaps the rod sticking - do they need to be greased? If it was the pipe would I be right in thinking it should do it most of the time?

It's odd because after the blip the other night it behaved and left my rather disgruntled mate standing in his Vectra 2.2 SRI - and he really was trying...the joys of having such an unassuming car
 

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I had a similar problem on my 2.3lpt, when you gave it full boot, it would instantaneously cut dead and then back on again, however once it was back on, it didn't go as well. It turned out to be the overboost cutout, which I was advised operated at 0.6bar (due to me running a high pressure 0.5bar wastegate actuator).
When I put a normal wastegate actuator back on again, it still did it although less frequently. I checked the boost pressure to be sure it was NEVER getting to 0.6bar, and then established that I had a faulty MAP sensor. This was telling the ECU that the pressure was higher than it actually was. Once the MAP sensor was changed, I never had the problem again.
I was waiting for the summer, to refit the 0.5bar actuator (no traction control), but never got round to it.
 

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Discussion Starter · #16 ·
How often did yours do it SJ? If the MAP sensor was faulty would it cause intermittent or regular problems? What's the rough cost a MAP sensor?

My problem has probably occured 6 -7 times in the last couple of months so I tracing it is going to be slow!
 

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It is probably worth disconnecting the battery for half an hour or so and then performaning an adpatation run to see if this cures the problem. Once overboost cutoff has been reaached, the threshold at which it wil occur will steadily lower with each repetition.

Adaptation procedures can be found here on BillJ's 9000 site.
 

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Mine did it almost every time I gave it full throttle, but then wouldn't do it again for a while. When you went to pass something, it would take off, get into it's stride and WHAM! hiccup hiccup.
Usually just about as you crossed the white line on to the wrong side of the road


Did it on the way to the dealer for them to investigate, then because it had done it for me, wouldn't do it for them at all in a good half-hour of trying.
 

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Discussion Starter · #19 ·
Been very busy so haven't had time to do any more checking - but have only managed to get it to blip once since my last post...so will continue to check to see if I can trace the problem.

As an after thought - could the idle control valve be a suspect?

In the meantime I will let you know if I find anything - thanks for all your combined help so far.
 
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