my mate has a vl turbo manual. he has a problem. When clutching to change gears under boost the revs dont drop but insted they increse to about 3000 rpm and then drop slowly to idle. has anyone come across this problem before, could it be a sensor or vacumm hose leak, something simple like that. Thanx!

is the butterfly in the throttle body closing properly, does it rev high at idle? is the tps connected?

What HARRIS said,Then check your ECU code's for any problem's.

is there any chance it could be something like the turbo lag kicking in?

yer he has checked the butterfly and it is closing ok. now were goiing to check ECU codes.

I no its an old thread but my car has been doing this for ages now and i cant work it out Basically when i change gear, instead of dropping instantly, the revs stay (or sorta slightly increase) for a second or 2 and then slowly drop, so its really annoying to drive and sounds so bad (like uve got no idea how to drive) It wont do it if i change gears at or under about 2500rpm Also it doesnt do it all the time, like on the odd occasion it just wont do it for some reason, but its not very often When its cold it doesnt really do it either Ive spent alot of time trying to pinpoint the problem with no success Just wondering if any1 else has had this problem or no's whats going on? coz this was the only thread i could find Any help would be much appreciated

Do you have an intercooler?? Were is the AFM located?? Do you have a catch can?? If so do you still retain the pcv valve?

Quote: Originally Posted by DeVL Do you have an intercooler?? Were is the AFM located?? Do you have a catch can?? If so do you still retain the pcv valve? No intercooler, its just a stock vlt setup AFM in stock position No catch can

check all the breather lines sounds to me like you might have a vacume leak.

Sounds like a sticky throttle cable to me.

Fuel in the carbon cannister is one other possible - though it would have to be a lot and under unusual circumstances, suggest not filling to top of tank and only drive around from 1/4 to 1/2 a tank for few days if nothing else to give it chance to purge <shrug> The other possible is the bypass valve, after a few years they might get sticky, you can (carfefully) undo the two philips head screws and take it out without dropping the pin, spray in some WD40 then put it back. Think this is called the AAC (Auxilliary Air Control) and its controlled by the ECU in repsonse to perceived load changes either the ECU has got it wrong or the valve is sticky or even the connections to it are coroded etc... Edit the AAC runs off the pipe at right angles to the throttle body so it gets air from intake in front of TB then to manifold through the valve,

DeVL - ive gone over all the possible spots (a few times now) where it could be sucking air in and all seems good VLHERO - ive checked this and the cable/butterfly isnt sticking at all Mike M - i hardly ever fill up above 1/2, most the time the tank is between 1/4 and 1/2 acc - the other day i decided to change the whole top half of the plenum to see if it fixed it, so i cleaned the plenum right up before putting it on (took the whole idle air adjusting unit off including the acc valve and cleaned out all the carbon/gunk) went for a few drives after that and it didnt do it AT ALL, so i thought ide finally fixed it, but no, the next day it just went back to doing it again... today i had another fiddle with it, swapped the acc and the air regulator, then took it for a few drives and its still doing it sorry its not easy for me to explain it all, but thats the best i can do thanks for your replies so far

You wouldnt have some carpet fluff or threads caught under the pedal...?! Ah just in case re AAC, unplug the connector for a few days and see if it happens again

Quote: Originally Posted by Mike_M You wouldnt have some carpet fluff or threads caught under the pedal...?! Ah just in case re AAC, unplug the connector for a few days and see if it happens again haha i wish it was that simple mate ok ill try that an see what happens

this was happening to my car when i bought it a few years ago. from memory the throttle position sensor nedded adjusting. It may not work for you but it did for me.

Quote: Originally Posted by vl_gigalo this was happening to my car when i bought it a few years ago. from memory the throttle position sensor nedded adjusting. It may not work for you but it did for me. yeah i thought it was that to begin with to (coz ive had it happen a couple of years ago and the tps was causing it) but ive adjusted it so many times and even swapped it with a couple of others i had laying around Mike M - i pulled acc plug off earlier and since then have driven for about an hour and it didnt do it at all, is so much nicer to drive now i still dont get how it worked but, i wasnt expecting it to make a difference at all or if anything make it run worse, anyway cheers for your help mate

Ah ha ! This suggests the relationship between the throttle butterfly position and the idle speed adjustment screw on the back of the AAC is outta whack andmight even reflect on the setting of the speed on the ECU itself. If the screw stop on the throttle body has been moved then the range of the AAC will be upset, wont affect an n/a much but will affect a turbo and more so if above factory boost levels. You will need the AAC, although at a narrower range, to handle such things as keeping idle high enough when larger electrical loads are placed on engine, such as high beam, air con, demister(s) etc. There are a couple of ways to handle this, the correct way is to ensure the screw and locknut is in the right position on the throttle body. It shouldnt ever be moved, so before considering touching it, take a close look and see if the resin on it is still intact. If it is then we attend to the AAC and if it isnt then it needs to be adjusted in concert with the AAC and the screw on the ECU... But for now, if you can have high beam and reasonable idle and aircon with the AAC plug out then it will also save a bit of fuel as well as be more predicatable to drive. btw. Best not to plug/unplug AAC connector when engine running etc. Anyway, see how you go with load issues for next week or so and let us know, Cheers

Re your PM directing me here -Sleepy-, might I suggest unplugging the connector to the AAC and leave it off for a few days to see what the effect is, if the problem goes away then it points to the general issue, then we know what to do Suggest re-read my post #17 and let me know via this thread the effect on revs going up, note the cold start will be a little more difficult but *DONT* touch the screw on the TB ever..! Cheers Some original photos have not been recovered yet.

yeah well its been a few days now with it off and its been sweet, have driven heaps and it hasnt done it

Ah ok, thats good, if it runs ok when cold and doesnt stall when the heater and/or headlights come on then the easiest thing is to leave it like that It points to a control systems issue from the ECU 'thinking' the engine is cold and on load and needing to be run a bit faster... If however you still want it fixed then first thing to do is make sure the screw on the ECU is fully anticlockwise and let me know if the TB butterfly stop screw has ever been touched - but dont touch it, just let me know if it has ever been turned and if the resin/red paint on it is intact ? Then we go step by step as I might have to check mine as well, Some original photos have not been recovered yet.