Idle racing and engine running on

GT5500

My gf's Astra coupe has recently started idling too fast and sometimes 'runs on' when the ingnition is switched off. At the weekend I cleaned out the throttle body and tried to spray some lube into the stepper motor, it was all quite smooth and free anyway. I also cleaned out the EGR which wasn't that bad anyway. What can be causing this? I suspect it may be an air leak or could it be the fueling. I gather the engine does not use a MAF to determine fueling so what does it use? MAP? or is it the sensor in the intake pipe? Hope you guys can help. Also forgot to say that the EML light has not come on.

vocky

certainly an air leak will cause a higher than normal tickover, make sure there are no split pipes, especially the servo and vacuum pipe to the fuel pressure regulator.

was the egr valve shut when you removed it ?

they should open downwards when energised

the z22se uses a map sensor, this sits next to the throttle body

GT5500

Ok I did the cam chain today, thanks to this site and some advice from Vocky, thanks for that. It wasn't too bad I am far from a novice but not quite an expert the astra coupe is very tight for space in the engine certainly seemed harder then people have described for the Veccy took me around 6 hours I guess. I think I caught it just in time as well, the old style oil jet was blocked solid as soon as I removed it oil oil poured out. Anyway I had a look round and couldn't find or hear an air leak, I also took the car for a drive and noticed that the idle is not always fast and sometimes it speeds up while you are at junctions. This to me sounds like a fault with the throttle or maybe the EGR although they seem to cause a low idle from what I have read. From my experience of air leaks they would cause the idle to race from the moment the car was started this is more like a sticky ICV (although obviously they don't have one). I have also noticed that when you start the car just before the starter engages you can here quite a loud whirring type noise this seems to have started around the time the fast idle started could they be connected.

vocky

a dodgy egr valve causes a lumpy tickover, it does sound like either an air leak or dirty throttle body

GT5500

As I said the throttle body has been cleaned and went back in nice and shiny, problem was as bad as ever actually my girlfriend thinks it got worse which leads me to suspect an air leak. I checked the servo and FPR pipes for leaks and any other pipes nothing was obvious. What is un air leak like is the way sometimes the idles is spot on other times it is high and sometimes it slowly gets faster. An air leak usually would cause the idle to be fast all the time, equally you wouldn't expect a sticky throttle motor to increase the idle speed at times it would just stick open.

vocky

I know that the cylinder heads can corrode between the inlet manifold and head mating face, but thats a long shot.

what about the fuel pressure regulator small black pipe or the blanking grommet(s) on the side of the manifold

GT5500

See above I already checked the FPR pipe, I am convinced that its not an air leak though because it doesn't happen all the time. Sometimes the idle is rock solid where it should be, this couldn't happen with an air leak. Other times the idle goes to around 1500rpm and slowly creeps up to 1900rpm and then slowly falls back down to 1500rpm almost as if someone is playing with the throttle pedal. I guess since this doesn't seem to be a common problem I need to wait until the idle starts racing and then play around under the bonnet and see if I find the cause, it would be nice to take the intake pipe off to see what the throttle butterfly is doing but I am guessing that taking that off will make the idle change anyway.

vocky

it might be worth trying another throttle body, or perhaps a new throttle pedal.

otherwise you have the intake air temp sensor, coolant temp sensor, coil pack, plugs, crank sensor and ecu left to try !

thats all there is in the electrical circuit.

GT5500

Unfortunately I don't have another throttle body but it may be the answer, what effect does the air intake sensor have? I used to have an xe engine and I know that the coolant temp sensor normally makes the car over fuel. The car does not misfire or lack power so I would think ignition circuit is not an issue, while the idle is fast it is no way lumpy and as said it almost seems as though the throttle pedal is being pressed.

vocky

secondhand throttle body's usually sell for £25-£30, might be worth putting a wanted ad in the classified section

if it doesn't cure the problem you can sell the throttle body for the same price you bought it for 🙂

as you say it does seem to be either the throttle body or the throttle pedal, possibly the ecu or a bad connection on one of the electrical plugs

GT5500

Ok so I did some deteective work at the weekend, I checked various hoses and unplugged the inlet sensor and the purge valve neither caused the idle to drop. I also took off the intake pipe with the engine running and the throttle butterfly was compleatly closed so there must be an air leak for the idle to be high. I sprayed around with carb cleaner and listened with a pipe and couldn't locate a leak so I guess I need to check the throttle body gasket and maybe the inlet manifold gasket next.

MikeS

could be an air leak in the egr pipe thus the engine is pumping in more air than when it should when the butterfly is closed

you can take off the air pipe with the air temp sensor connected as it doesnt regulate the air flow but it wont make much difference

i would say it is related to something post throttle body

a coolant temp sensor controls fuel and air - you could try replacing that

GT5500

ephid0r said:
could be an air leak in the egr pipe thus the engine is pumping in more air than when it should when the butterfly is closed

you can take off the air pipe with the air temp sensor connected as it doesnt regulate the air flow but it wont make much difference

i would say it is related to something post throttle body

a coolant temp sensor controls fuel and air - you could try replacing that

Coolant temp sensor controls fuel throttle butterfly controls air, if the butterfly is closed (which it is) and more fuel is added the engine will slow down, I suppose it could be running lean which would increase the idle speed but I would expect driveability problems and high temps. I did find something interesting though when I unplugged the intake temp sensor the idle got slightly faster, I will check it with and ohm meter.