A VERY frustrating problem. After a small free rev, it will head towards stalling, by dipping low in revs, but not stall. The higher I free rev the more likely it is to stall when it comes back down. Similar symptoms happen when actually driving, and if I don't hold the car in gear when slowing down (to around 2000rpm), it will stall. I have done the usual Idle control unit clean, check, adjust and so on. I have checked for air leaks. TPS is set correctly. Fuel pressure is ok. All engine bay electrical connections have been removed, cleaned and refitted. Fuel filter, plugs and so on are all in good condition. The idle adjustment screw makes NO difference to idle speed at all (the seal on the idle screw is in good condition). When using consult and trying to adjust the base idle, as soon as I switch off computer control of the idle, the car will stall (regardless of where the idle speed control screw is). Another thing I noticed is that from a dead cold start, the car will instantly rev to 3000 or so, before coming back down straight away to 1200 or so...and then slower lower as the engine warms up. The engine has had modifications. It is a twin turbo. Even though I have checked for air leaks, I am suspecting this is what is causing the problem...would like to hear other peoples ideas?...
leaks I have issues like this in the past, and was casued by a big air leak . do you have a CAz air leak tester tool so you can see that your intake is indeed building up pressure on the gauge?
your not running doolz or anything like that . id say your air filter is in a turbulent spot. try using some duct tape or repositioning the filter so that it is not in a direct path for air
I tried to limit the info I first gave because I didn't want to unnecessarily complicate finding the problem... I am running a duel pod filter setup. I have rechipped the ECU to allow for the difference of air values and so on. Regardless of trying to fine tuning the values, it makes no difference to the symptoms. The symptoms actually started before I did this mod anyway... Regarding the duct tape...the problem is when the car is stationary and in motion, so the 'ol duct tape trick won't do anything... A bit more info...I have actually tried another AIC/AAC/AICV unit (or whatever it is called) with no difference to the symptoms. I am still heading towards an air leak problem. This problem initially was very mild, and got worse gradually worse over a few months, to the point where it is now... I actually have a caz blowup tester here. Can anyone tell me exactly the method that is supposed to be used to test for air leaks?
Yeah mate, spot on exactly the same as yours, you may find the leak is so big (mine was) that I had to pump a much larger volume of air into the intake than normal to be able to find it.
tps should be set at .45 ....it will probably flicker between .44-.46 this is fine... do you have bov's ? alot of people have had stalling problems from bov's ... if the aac valve is not doing anything when playing with the screw then you need to pull it out and thoroughly clean and test as per tech article in tech section. did you test the aac valve that you tried prior to installation to your veh? regardless i would still take yours ouit and thoroughly clean it and test for proper operation...step by step guide is in tech section... for boost leak tester remove the filter, and plus the caz boost leak tester to the t-piece, and pump no more than 7-10psi into the system...listen carefully for leaks, locate and replace hose leaking...
Fixed! After checking with the blowup tester, I found a leak at the left hand side turbo compressor outlet hose. The clamp was loose. I tightened it a fair bit. Also, I fo0und a split in the right hand throttle body hose (which is still to be replaced. After restarting and retesting I gave it a few good free revs, and now it idles like it should! Yet to road test but I have confidence it'll be ok... Thanks for all the suggestions from those that replied...
remembering this thread, i just had the same symptoms, turned out to be a blown turbo compressor outlet gasket, and the bolt to hold the elbow on had worked half way off. i think the car running so rich maybe contributed to the o2 sensor dying (or it was a coincidence)
Had similar Problem I had a similar problem on my 300 when i installed some blow off valves and they were leaking (btw dont every buy bovs from ebay) It would dip down as you say till nearly stalling then recover. A couple of times when turning a corner, push clutch in changing gears ..engine stops...no power steering. After replacing bovs with turbosmart...no more probs. Skooba
