Club G40 Forum
Technical => Engine and Transmission => Topic started by: wbaxter90 on October 06, 2010, 11:19:58 am
-
span out in 1st and hit limiter, quickly changed up, seemed fine then got stuck in traffic, and with the clutch down it revs its self to 4500 then back down, over and over.
pulled in at tesco, got out the car and it was revving itself with no one in it!?
got it home, disconnected battery let it cool down, started it up and idled ok, tapped the accelerator a tiny bit and the revs shoot up to redline on there own and you have to quickly pull the key out to stop it.
so what now? idle valve?
-
possibly an air leak somewhere? Check all the pipework in the engine bay
-
ok will do, didnt realize a leak would make it do that!? when you say piping, do you mean boost pipes etc? or just everything?
-
esp the pipes to the aux air valve I guess. An air leak below the throttle plate will make it idle high yeah, bigger leak, higher the idle.
-
checked all the pipes i could see, had the boost pipe off, and tightened all the intercooler pipes, still the same, idles high and tap the accelerator and the revs shoot up quickly and you have to quickly pull the key out. do you have a pic of the pipes i need to check?
-
no but they are under the inlet manifold, one goes from the top boost pipe to the aux air valve and then the other comes from the other end of the aux air valve to the bottom of the inlet manifold. These pipes are about half an inch outside diameter. It's not going to be the big boost pipes as they are on top of the throttle plate, a leak in one of those would cause a boost leak but shouldn't affect idle speed.
-
orite ok, il have a closer look, i take it these are very hard to get to?
-
had a good look and they seem fine? what else could it be?
-
inlet manifold or t/b gasket
-
what are broken? what do you mean?
-
I've had this before. Ended up being one of the small White pipes popping off. Simple as.
Sorry I can't be more precise but was a loooooong time ago.
-
white pipes? please please please can some one get me a pic or something, the cars for sale and then this happens, so really need to get this fixed
-
Boost return jammed closed maybe?
-
Boost return jammed closed maybe?
seen that before.
Although a jammed boost return valve wouldn't allow the car to rev up and down, only up.
Wayne, remove your boost return pipe and boost pipe and check your throttle body, even as far as removing it anyway and check for correct operation. Possible your linkage for boost return aswell?
Does sound like a vacuum leak. Possible a split in your ISV valve/inlet manifold pipe underneath perhaps, ISV trying to overcompensate? Or as pete has said, TB/manifold gasket. Check white tube aswell from brake servo one way valve and correctly connected to your ECU, with no damage (ive seen one chaffed once, where someone incorrectly routed it). How are your brakes btw? I.E. one way vavle not knackered. You can get a spray to check for vac leaks, goes purple or something.
-
you would need asevere leak for it to rev that hgh, its not going to be just a small pipe or gasket, id be checking lnkage on throttle etc, or cable,
to check for leaks get your self an aerosol of "carb cleaner" and spray around all joins / pipe fittings BELOW throttle butterfly, if the engine note changes this is where the air leak is
just cant see it reving that high from an air leak, doesnt make sense, even if you take off completely the isv pipe to manifold it wouldnt rev to redline
-
still the same, the interiors back in for the sale, just need to fix this gay rev thing! il get a video 2moro, and hopefully itl give you guys a better idea because i havnt a clue!
-
Hmm, re-reading this. realised you said it wasn't revving up and coming back down, it was staying there up at redline, and starting engine it idles, albeit high and as soon as the throttle is pressed it revs off the scale.
defo check out your throttle body out for a sticking mechanism. Best best would be remove your throttle body, good strip and clean, replace TB/manifold gasket.
Have you had a chance to look around the throttle body yet?
-
well, when it firsted happened it was reving itself up then down, then when i got it home and let it cool down etc and tried again it just revved right up and not back down. i checked the boost return butterfly thing and all seemed fine, is removing the tb hard? anything i need to do? or just undo the bolts holding it on?
-
4 bolts, 5mm allen key heads iirc. gasket may tear if its not been off before, but always good to replace that anyway.
Remembering back to days of old, i recall when i first fitted my 51mm throttle body that liam withall machined up (2nd prototype), chucked it on and it revved to redline. Throttle butterfly was getting stuck at WOT, not always but if you slammed it WOT it would stay there. Took it off, stripped it down and filed it slightly better and worked perfectly.
-
what so your saying i should take it off, clean it and replace gasket. whats best to clean it with?
i checked today and to edit my first post, it doesnt rev to redline it just shoots up the revs from a tiny tap on the accelerator, and i take the key out as i dont want it revving that high from cold tbh! but the revs do go high but not redline.
-
Try it without the boost return pipe connected first.
-
is it more simple just like a sticky throttle cable .
when it next doeas it , swith it off and see wherethe throttle flap is, it may be off the idle stop, a small gap but hanging open will raise the revs,