tommye

Dear listers,
I have now removed the LBE and the car is 100% stock. I still sometimes get violent cutouts after a longish WOT run. Indicated peak boost is 1.8 bar.
Sometimes, idle is bad just after a cutout.
Apart from overboost, what else can cause these cut-outs ?

Tommy
(getting slightly frustrated...)

toddk911

Fuel cut.

theedge

Weak coil, worn out cap/rotor, bad spark plug wires, bad spark plugs, too large of a plug gap all spring to my mind.

hosrom_951

Bingo!!!

After closely inspecting my coil/wires/plugs and leads, i found some green rust material inside the coil. The coil was also a little wet (yes, found water not condensation in there).

I need a new coild, but again i mentioned all this in my thread (coil+clutch master/slave cylinder'.

Tommye: Closely inspect the ignition system (cap, rotor, coil etc). The best method i know of for testing the plug wires is to run the car in a dark place and watch for some spark comming inbetween the wires themselves (i guess that is the ONLY way to see if they are worn anyway).

Could you also check out my recent post regarding 'overboosting at WOT' which MAY be the same problem you and I are facing at the moment.

UK952

Might be worth swapping the DME relay as well, relatively cheap and worth having a spare handy as if it doesn't fix it this time they are a comon failure,
Tony

ilikemy944

I have $1 on the TPS. (if it only happens while at wot)

tommye

TPS - that sounds possible, is this a wire-wound resistor track with a slider ?
Can it be cleaned ? Is there a WOT switch as well just like the idle position switch?

I would rule out ignition problems since the KLR goes into overboost condition.

The problem only happens at WOT and only at full boost (except for afterwards when the KLR seems to limit boost to 1.2 during a minute or so and makes the engine cut violently for every attempt of going past 1.2bar), and it does not happen all the time - sometimes it works perfectly.

Someone suggested the fuel pressure regulator after having had similar trouble, any thoughts on this ? Would this trigger the overboost-like fuel-cutouts?
This leads to the question that I do not have an answer to yet : does the KLR/DME in any way detect lean fuel/air conditions in order to cut-out fuel or whatever is needed to protect the engine????


Any help appreciated,
Tommy

UK952

If its definately overboost might be worth a check on the signal line to the wastegate they go hard and brittle due to the heat, so the end could be leaking trimming half an inch off usually gets you back to a flexible bit.
Tony

Porschefile

I highly recommend checking your plugs first. I've been chasing down my boost problems for the last ~3 months. I've had sporadic problems and replaced the following in my attempt to cure it:

Plug wires, Cap, Ignition coil, retarded timing 3 deg. w/ position 5 on the Dme FQS, replaced plugs multiple times, replaced all vacuum lines, 3 bar fpr, eliminated cycling valve with EBC.

The solution to my problem was plugs. I highly recommend AGAINST using platinum plugs. I used Bosch platinum's, and even tried 1 step colder Bosch platinums (which increased the boost cut/misfiring). DO NOT USE PLATINUM PLUGS! I don't understand it but every single car I've owned, that I've used them in, has made them run worse.

tommye

Porschefile
The KLR/DME definitely goes into something that looks like "overboost" mode after each time I get the violent cut-out. i.e. repeated violent cut-outs every time the boost gauge goes beyond 1.2 bar. This clears after a minute or so and things go back to normal. As far as I understand, this is normally due to a detected overboost condition.
How could an ignition problem trigger this mode ?
Plugs are fairly new original BERU:s from the official dealer.

Tommy

Danno

If you hit overboost, check the error codes from the KLR, it'll tell you that for sure.

Any kind of leaks in the wastegate-control hoses (not vacuum, they're under boost), would tend to cause leaks, which results in increased boost. I would hook up an aftermarket gauge to verify boost levels since the dash gauge is not the most accurate.