mk2 16v KR wierd idle

Evening chaps (and chapesses),

I am have noticed that my GTI is idling in a strange way. to be honest, it has been the same in the few months that ive owned it but other things have taken priority. Anyway, whats happening is it has quite a rough idle when its hot or cold, ive set it around 950rpm but I notice this tends to fluctuate. The main issue is that when you give it a rev it then settles to about 1200ish and then returns to 'idle' over about 10-15 seconds,

Can anyone give me any pointers?

Thanks

Tom

 

Hi Tom,

Have a look at RJs guide...
http://www.clubgti.com/showthread.php?t=195423

Work your way through that and if it still isn't sorted then post back and we'll start looking at other things.

It could be one of many things, or even many things together lol. I'd have a look at the wiring to the 3 temp sensors on the side of the head and he check for any split vacuum hoses around the engine bay.

 

Air leak is where I'd look too and check ISV if it has one.

 

The idle switch it fine, you can hear it clicking and if you move the throttle half a mm off it you can hear it coming off the idle circuit. I have cleaned out the ISV, will have another go tonight.

Noticed that the idle screw appeared to be doing nothing last night ie no effect when screwing in/out sprayed brake cleaner into it to see if it was leaking and im confident it isnt. Do you need to unplug the ISV to adjust idle speed screw? sweear ive managed it before without unplugging

Thanks

 

cheers, will give this a go tonight. you mean the -ve single red/black with its own connector right?

 

alright guys,

Ive tried doing the idle and set up and its beach. The idle screw does more or less nothing and the CO screw is too stiff to adjust with a normal allen key (?). Checked the static timing and the TDC crank and flywheel marks dont line up with the dizzy and cam, like it is one tooth out or something. I figured it wanted rectifying and thought it may be a good time to change timing belt. Anyway, the intermediate gear doesnt have a mark on it as i expected it to.

In the haynes manual it says to line the intermediate gear with the crank pulley, is there another way to determine its orientation?

I have checked, checked and rechecked for vacuum losses but cant find anything. the only thing im not completely certain of is the big pipe out the back into the servo. Its fine up to the yellow (valve thingy) but if there was a leak after this would it still affect inlet vac? Also there is no servo assistance , so could these both be caused by the same thing?

 

The intermediate pulley only drives the oil pump so it is not necessary to align it with anything.

When you were tinkering with the idle screw did you have the ISV disconnected?

If it was, and the idle screw makes no difference then I would have thought you'd definitely have a vac leak somewhere as the engine will be running from the air coming in via the leak rather than the air coming in via the port for the idle screw.

If the ISV was still powered, then that's probably why the idle screw makes no difference.

The yellow thing is a non return valve, if that fails then air will leak back into the inlet. You can disconnect if and blow through it, you should only be able to blow through in the direction that the arrow points (towards the servo I think)

With the cam and crank timings marks, once the head has been skimmed etc, it can be quite hard to get it all bang on and can sometimes be half a tooth either way. How far off are the marks? Although if the belt is due for a change then it's probably a good idea to swap it. Do the tensioner as well while you're at it

 

The more I think about it, the more it sounds like the one way valve (yellow thing) is faulty. That would explain the lack of servo assistance and the vac leak that's stopping the idle screw having an affect

 

you reckon Ben?

But, Wouldnt it then just make a constant vacuum in the whole pipe though? Or does the valve allow a vacuum into the servo when the pedal is pressed?

 

To be honest, all I know is that it's a one way valve lol. If it was letting air back through then you'd have a vac leak. I'm not sure of the effect on the servo in this situation. It's been a long day of overhauling brakes and MOT preparation so my brain can't work it out lol

 

Im prepping for an MOT too, but given your on brakes i suspect your a fair bit ahead of me

Any thoughts on my timing marks?

 

I'm all done MOT wise after today. At least until it fails on something lol.

As I mentioned above, the intermediate shift only drives the oil pump so doesn't need aligning with anything.

With the cam on its TDC mark (arrow at the top on the side of rocker cover) does the dizzy line up with its TDC mark? As in, are they both pointing at TDC at the same time?

Same for the crank pulley and flywheel, do they both hit the TDC mark as the same time?

The above is to rule out a sheared key in the crank or cam shaft.

If the crank/ flywheel are both on TDC at the same time, and separately, the cam/ dizzy are too but the flywheel and cam are at different points, then the belt could be a tooth out. Although once the head has been skimmed, it can end up always being half a tooth off. Have you got any pics?

Which mark are you using on the flywheel? There's 2. One for TDC, and one for 6* ahead of TDC used for setting the ignition timing

 

Sorry for pestering Ben, didn't see you'd posted twice!!

i had a quick look tonight and im fairly sure the crank/flywheel line up well (with the little flywheel, notch for TDC not 6 deg bTDC)

So to set this up for swapping the belt what position should i put the engine? I was gonna just stick it all into TDC and put the belt on then tension?

Cheers

 

Yeah, that's pretty much it. It might take a couple of attempts to get it right though.

When you tension it up, it will likely rotate the top end slightly pulling the timing out by a tooth or so. I find that deliberately spinning the head back a tooth or two before tensioning it up usually pulls it all into line once the tension is correct. You'll see what I mean when you tackle it.

Once it's tensioned, check all the timing marks, and then double check the timing marks.

Once you're happy that it's lined up, pull the spark plugs out and spin the engine over a couple of times by hand. I use a breaker bar with a long extension in through the wheel arch with a 19mm 12 point socket on the crank pulley bolt.

Give it a couple of turns and recheck all the marks are still lined up. If so, then you're good to go.

For me, the worst part of doing it is turning the key for the first time after doing it.

Ive got a brand new Gates belt for a KR in the shed if you havent got one yet? I bought it without thinking and then remembered that I have an ABF lol

 

Ben, RJ

Ive got the belt on but wanted your ok before i stuck everything back together:

this is the flywheel position when cam is cock on TDC. Bear in mind the angle of the shot makes it look a little further away



its a tiny bit out to my eyes but less than a tooth of adjustment and positions either side are way further away. Ive turned it for 3 cam revs and all ok.

as for tension, i have done it as best i can, i can twist the section between cam and oil pump drive about 80-85 degrees in the middle if i really try, do i need to go tighter?

Cheers

Tom