I have come across one of the weirdest things ever. What it does is starts, it barely idles, so i just give it a tiny bit of throttle to keep it alive, then anywhere from straight away to about 15 seconds later, without warning it just starts reving up to 5000rpm all by itself. So i just switch it off. To save some questions i'll state the setup and what I have done thus far. It is running factory ecu and loom. Originally I had it running with the standard plenum and cross over pipe and it ran perfectly fine. As far as the leads, timing, injectors etc, they have all been left alone. What i have fitted since then is a front mount cooler, the AFM is in front of the turbo at the moment (factory position) But I have also fitted a forward facing plenum with a XF Throttle body. Speaking to guys on the forum before i done all this, they said you can do away with the AAC Valve that usually sits on the standard plenum as you can adjust the XF throttle body to allow air through to idle. But what on earth could cause so much air flow in to rev up to 5000rpm by itself. All hoses and clamps are tight on piping, the plenum only has 4 vacuum outlets, 1 going to fuel reg, 1 for the brake booster and the other 2 are blocked off at the moment. Does anyone have any ideas i could try? This was the first time i have fired it up in about a year. So im a bit devo'd

you don't say so but I'm guessing you're referring to a VL turbo have you checked the throttle cable activation to make sure it is returning normally and not staying open when you push the pedal

Yes its a VL Turbo, sorry guys Yes I have. After it done it the very first time i presume throttle plate. So I took the pipe off and just played around with it and it springs back everytime without hesitation. So it definitely isn't that, because also when it just randomly springs up to 5000rpm I haven't even touched the throttle for it to get stuck.

After doing some more testing, we have narrowed it down to being air leaking in somewhere after the throttle body, Because we fired up, covered up the throttle body and it still manages to run by getting air from somewhere else.

After taking the plenum off and placing it up against a straight edge, it wasn;t the best. So I got it machined flat again and refitted it with a brand new gasket. Hoping this would solve the problem, but it is still the same. So I have eliminated the chance of air leaking through the manifold and head. Does anyone have any ideas at all?

Quote: Originally Posted by aus880 [View Post] you don't say so but I'm guessing you're referring to a VL turbo Pretty safe assumption you goose. It's a VL turbo based forum and his username has 'VL' in it, with a picture of a VL in his display.

And he talks about XF Throttle bodies on a forward facing plenum

And he still has problems lol

Have you done a diagnostic test?

I wonder if removing the AAC might have something to do with this. ECU not knowing how to handle idle correctly?

That's exactly what I'm thinking. Like I tested it ages ago, by removing all those plugs, turning it off and firing it up again and it ran ok. But that was when I had the car connected with a battery. Now that it has been about 6 months with no battery in the car, i'm just wondering if maybe the ECU needs all factory sensors plugged in to regather it's tune and information. It would help if i knew someone that had a running VL Turbo, i would quickly switch computers and see if it makes any difference at all. I have spare ECU's but they have all been unplugged for even longer.

Shouldn't make a difference. I'm pretty sure factory ECU's can't loose their memory Run diagnostic test a tell us what codes appear. Red represent 10's & Green represents 1's (ie. 2 reds & 2 greens = 22) There is also another helpfull thread. http://www.calaisturbo.com.au/showthread.php?t=165781

Cheers man I will try and do the diagnostic. It does say in the steps to start the car and let it idle. Mine wont even idle. So does the diagnostics still work with the car in just ON position? Or does it really need to be running?

The OEM ECU will loose idle/light load cruise mixture adjustments if disconnected for a few minutes. The ECU will fail back to factory default settings which are often a little lean. VL ECU's can't control idle much over 1500rpm with stock idle motors, best wind the ecu adjustment anti clockwise just incase (about 650rpm). Sounds to be an airleak through a bolt hole or gasket fitment. some of the forward plenums i've seen are not even worth melting down. need to grab some water in a spray bottle and go nuts all over the inlet manifold to try and get the leakage to suck up some water. you'll soon be able to control the rpms and find the leak. keep in mind to rev a motor to 5k doesn't take a really big leak, its just simply a matter of the engine generating enough power to over come the friction it takes to maintain a contant rpm. the idle motors don't cause any error codes, nor does leaving the exhaust gas oxygen sensor unplugged. the only one of interest is the AFM/MAF error '12' but I can't see it causing the problem you describe. Must be an airleak that develops, as you have a forward facing plenum most of the idle control is missing anyway. Needs to be manually adjusted now.

Thanks bachig24u. This is the exact fault we first came up with. I mean at one stage I was able to have my hand right over the mouth of the TB (while it was reving hard) and apart from sucking the living shi7 out of my palm, it was still reving. So we thought the air has to be coming from somewhere. After taking the plenum back off and checked with a straight edge, it wasn't looking good at all. So it got machine back to dead straight flat and we refitted it with a brand new gasket. Thinking for sure that was the problem. But little to our surprise it done the exact same thing That's why it has us all stumped. I had to move house on the weekend and the Calais got a Tilt Tray ride to its new home. I will be having another crack at it on Saturday, so thats why any info and things to try will be much appreciated. Boosted Wagon is also helping me out as he has done this mod a few times and wants pics of the engine bay and set up to see if he can pick up where I have gone wrong as its very hard for others to rectify problems when its just txt. I might even do a short video of what its doing and post the You Tube link up in this thread, so everyone can see what it is doing and how its set up. Some original photos have not been recovered yet.

Quote: Originally Posted by VLC-57L [View Post] I might even do a short video of what its doing and post the You Tube link up in this thread, so everyone can see what it is doing and how its set up. Great idea!!!

Ok sounds like a video is definitely the best way to show the fault. I'll do it on Saturday. Stay Tuned Some original photos have not been recovered yet.

Ok I have done 2 videos. 1 is a quick pan around the engine bay to show set up (dont mind the things cable tied, was just so i could try and start it up). The other video is 2 attempts to start, then eventually 3rd time it starts, revs up to 4000rpm and then i shut it off. The banging in the second video is not my car, but a bloke next door working on a house. I have PM'd you guys the vid links.

Might be a dud AAC valve. Have you tried running it with the AFM disconnected. Remove the plug on the AFM & see if it acts the same. If there's a change in engine characteristics that would usually mean it's working. If the AFM is working fine. Remove the plug on the AAC valve & see if it acts the same.

The AAC Valve is not hooked up at all. Thats still sitting on the stock Plenum. Guys have told me you can still run the standard ECU without it being plugged. But we did try the afm not hooked up and it just wouldn't start at all.