16v Running issues

Hi,
Recently finished my 16v conversion and was running sweet, started straight off the key and idled lovely.
Had to replace my fuel lines as one had split, finished that today and started it up……………

After 5-10mins of running lovely it just cut out, i went to restart it and it took a while but then started and now idles at around 3K!

Has anybody any ideas? have to sort this out as i have my MOT on Tues morning

Idle screw loose and fallen out? Something loose in the throttle body? Big vacuum leak? Basically, the car is getting too much air into the engine, but the fuel system is still working and seems to be supplying enough fuel to let it rev to 3000, rather than leaning out massively and either not running or running lumpily, etc. Hence probably a throttle issue.

Whipped out the throttle body and all seems ok, nothing loose or alike.
All the inlet piping seems fine and there don't seem to be any major vacuum leaks.
Paul_c like you say it seems happy enough to idle a 3k its till smooth etc (not that i have left it running for ages).
Possible a metering head issue? this wouldn't be an airlock somewhere would it?

Its 100% not the metering head or an airlock, its something AFTER the throttle body ie vacuum leak. Do you have access to a smoke machine? If not then I think you can squirt white spirit (or maybe even WD40) at various parts of the induction system, to see if it changes the note of the engine. How about coarse idle adjustment (screw on the throttle butterfly)? How about vacuum hose to the servo, or a faulty servo? etc. Basically you need to check a lot of vacuum hoses, and there's a lot of a fully plumbed in 16V motor. Oil breather too, etc etc. 5th injector…

Havent got access to a smoke machine, sure i can find it though esp if its def after the throttle body.
Surly if it ran lovely before it wouldnt be any of the adjustment screws? like you say must be a leak sumwhere

Right, all vacuum lines and connections replaced - no luck.
Tried blocking off the vacuum connection from the inlet manifold (the one that goes to the servo etc) - no luck.
Checked gaskets and connections within the inlet manifold assey - no luck

any more suggestions?

nb also now have a vacuum gauge connected and that shows idle when its at 2.5K?

Could this be an ISV/IAC issue? wondering as its the only way for air into the engine without passing through the throttle body

KV84 said

Right, all vacuum lines and connections replaced - no luck.
Tried blocking off the vacuum connection from the inlet manifold (the one that goes to the servo etc) - no luck.
Checked gaskets and connections within the inlet manifold assey - no luck

any more suggestions?

nb also now have a vacuum gauge connected and that shows idle when its at 2.5K?

Could this be an ISV/IAC issue? wondering as its the only way for air into the engine without passing through the throttle body

What's the actual reading on the vacuum gauge, in units of pressure? I can compare it to my idle reading.

Yeah sounds like ISV issue, disconnect it and plug the holes up and see how it behaves.

paul_c just tried that, took it off and blocked air supply from that point on - coughed on the first turn and then wouldnt start at all.

From that i would think that eliminates a leak after it otherwise it would run and also no leak elsewhere otherwise the leak would supply air?

KV84 said

paul_c just tried that, took it off and blocked air supply from that point on - coughed on the first turn and then wouldnt start at all.

From that i would think that eliminates a leak after it otherwise it would run and also no leak elsewhere otherwise the leak would supply air?

I don't understand - are you saying there is a leak elsewhere, or not a leak elsewhere? I'd say you've found the leak (the ISV) and that its now no longer running because the idle speed and mixture need to be reset to make it run within spec. I don't suppose you still have your AAV do you? Or, a spare ISV, or able to clean/check the ISV you have.

yeah no leak elsewhere - well other than the ISV.
Left the AAV on the old 8v when i sold it
Going to call in a favour off a m8 with a 16v rado and try his  

Annoyingly can get another ISV to test till tomorrow night.

Wouldn't be the wiring would it? surly it wouldn't have run fine for the last 3 weeks if it was (Im no auto-lecy, but my electrics arent bad)

thinking about it when the engine origionally cut out and i went to restart it the ISV sounded different to usual - a smoking gun maybe?

I don't know how you've wired your ISV. But it could be the wiring, and also you can check this by trying your ISV on the Corrado. Don't fit his ISV to yours until you've done this, just in case your bad wiring damages his good ISV…..


In fact, AFAIK nobody's done a guide to wiring the ISV in but its just a module and a couple of wires?

paul_c said

In fact, AFAIK nobody's done a guide to wiring the ISV in but its just a module and a couple of wires?

1/2 through a guide to go on the forum - sort of an add-on for anybody who wants the full setup.Its a little more than a few wires but its not rocket science >> not going to finish and post it until mine is sweet though  

Bit of progress made, cleaned the ISV >>

It now starts happily enough and idles at 1500 rpm before rising to 2000 after about 10-15s

I suppose really it would be cheating to just adjust the idle - loosing the will now

No, there's an idle speed adjustment which is required to set a "baseline" idle speed on a car with an ISV.

Is that the one on the metering head? What type is it  - allen, hex?
Seems odd that is was fine and just like that the idle changed.

no its on the throttle body. ive found that swapping metering heads about has a marked effect on the idle, i assume the same would be true if you fixed leaky fuel lines?  try the idle first though as its easy. another thing, maybe the oring has gone on the screw, mate of mine had probs with his constantly backing out on his 9a, i had the same on my 8v too. all the screws are discontinued from vag now
I got a big box full of orings, it has a size in there perfect for 16v idle screws

To set idle on 16v equipped with working ISV control unit:
1. disconnect red/black wire from coil (if done properly there should be a seperate spade plug with a wire from here to isv control unit)
2. disconnect breather pipe from block and route so only fresh air can be drawn in
3. Allow engien to warm to at least 80 degrees oil temp

adjust idle to 1k rpm, and tweak CO to 2% if you have decent sniffer gear to hand.

Oh and make sure the ignition timing is setup right before you set the idle/co

News
Have now tested all of the piping to the ISV and the ISV with no luck.

rubjonny PM sent

Cant adjust the idle back any more,  tried the idle adjustment proceedure but with the ISV connection unplugged it idles at just under 4K

Has to be an air leak. Can someone confirm my thoughts here:


TB obviously governs the inlet of air into the inlet system
Depending on air demand the pressure plate in the metering head regulates the fuel sent to the injectors

During warmup/idle the ISV delivers air into the system when tb is closed

The ISV bypasses the throttle body, so if its not the throttle partially closed, or an air leak further up, then its the ISV.

You could simply disconnect, remove, and block up both sides of the holes?

Sounds like you either have a faulty ISV or the wiring to it is faulty, which means its fully opening instead of doing its job and regulating the idle speed.



Ignore the metering head - it simply measures whatever the airflow into the engine is, and supplies the relevant amount of fuel to make the correct air-fuel mixture. It doesn't influence (well it does but negligably) the actual amount of air flowing, just measures it.