Before I start.. I know naff all about engines.. But here's what my problem is.. The car idles roughly, bit up and down. When driving the acceleration is very jerky. Also there is a lot of over-run on the engine when easing off the accelerator or changing gear which makes me sound like an amateur driver! A couple of my mates have driven it and noticed the same thing. The car has just had a bit of a service which included.. Oil flush and change Oil filter change Engine coolant flushed twice and changed with readymix New spark plugs New fuel filter I've ran a couple of bottles of fuel treatment through but it's not made any noticeable difference. The car has a K&N induction kit which could probably do with a clean but seems to be sucking plenty of air through. When I had a new rocker gasket and new belts and tensioner fitted I asked the guy to check my throttle body guessing it would be clogged but he said it was fine. Anyone got any clues?
I've just had a rocker gasket replaced and the cam belt changed and i've had exactly the same problems as described above. Mine's a Mk2 16v. Any help would be greatly appreciated
check you timing, this can lead to rough running if it is out after a cambelt change. plenty of info in these forums about timing/ static timing.
Oops sorry, it's a Mk3 16v GTi. The car was timed and setup when the belt was done although the problem has existed since i got the car in December
do they have an overrun cut off valve on the airbox? i know my mk2 valver does and if so it could be stuck open... there is also a relay behind the centre console that controls the idle valve and the overrun cut off valve. if its not working / lost power/ earth this could be the answer... I know this applies to the mk2 but not sure if the mk3 has the same setup
Hopefully it's something the VAG com software will pick up but i've not got the laptop at the moment to run a diagnostic scan. Although i'm pretty sure the software will not detect and faults with relays?
Just bought some 4mm silicone hose to replace the vac hoses, as mentioned in another post about jerky running on a 16v. Soon see if this makes any difference!
Took mine into the garage yesterday and spoke to the guy who replaced the rocker gasket. After a couple of minutes searching we found the source of the problem. On the throttle body there's a switch which gets depressed when your foot isn't on the pedal, telling the computer that the engine's idling. When you push down on the pedal it releases the switch and allows the engine to rev. My switch was getting stuck so that even when I put my foot down the computer thought it was idling, hence why it jerks (confuses the computer). So check that this switch isn't sticking (assuming the set-up is similar on the MK3). I played about with it with a bit of WD40 (when the engine had cooled...) and just flicked it in and out repeatedly. I also pushed the throttle up to the max with my finger and let it snap back into place, as I was finding the button only stuck when it was depressed with force. After a while of fiddling I freed it up enough so that no matter how quickly I closed the throttle it still switched off when I pushed the pedal again. Took it out for a drive yesterday evening and had no problems what-so-ever! Hope that helps
Awesome, thanks! Well i've got the new vacuum hose coming and ive got a new throttle body coming from headtune which has been fully restored, machined and polished. When these are on along with the new chip i'll see if the problem goes away!
my 8v mk2 was well jerky once. it turned out to be the microswitches, they were covered in crap. quick wipe and i was fine again
the mk3 16v does have the same closed throttle switch. worth a look. i had to get a new one because my switch was telling the ecu that the throttle was never closing
If anyone could give me a few clues as to where to look for it it'd be much appreciated! Wipe with some WD40 or brake fluid would clean it up right?
follow the throttle cable to the throttle. when the throttle is closed it rests on a throttle stop. the switch is basically the throttle stop
also... you have a cone filter. did they properly blank off the little vac hose that used to go to the airbox?
Just had a look, there's a a few things kicking around which i dont know what theyre for, ones a big pipe that appears to come from the manifold which i'm guessing just takes the heat away from that? On the throttle body theres 2 cables, one goes to some round plastic siemens thing and the other is a very thin cable that's attached to nothing, i'm guessing that's the vacuum hose you meant? It doesn't appear to be blocked off at all
