16v Running issues

For info, when I initially got my 16V running, I junked the ISV and blocked up the pipes. Later, I plumbed in the AAV and it works reasonably well. Also because the engine is quite good condition, it idles smoothly anyway, so no real need for an ISV.

paul_c said

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 negligibly) the actual amount of air flowing, just measures it.

Faulty ISV and assoc pipework have been ruled out - swapped them out this afternoon to no avail (And my ISV ran fine in my m8s rado)

Metering head - My thoughts were that if there was an external leak allowing air into the system then surly the metering head would not enable the correct air/fuel ratio. I know what your saying paul_c,was just trying to eliminate sections of the system

paul_c said

For info, when I initially got my 16V running, I junked the ISV and blocked up the pipes. Later, I plumbed in the AAV and it works reasonably well. Also because the engine is quite good condition, it idles smoothly anyway, so no real need for an ISV.

so with the pipes to the ISV blocked off it should run fine?
Therefore if it doesnt its elsewhere

KV84 said

paul_c said

For info, when I initially got my 16V running, I junked the ISV and blocked up the pipes. Later, I plumbed in the AAV and it works reasonably well. Also because the engine is quite good condition, it idles smoothly anyway, so no real need for an ISV.

so with the pipes to the ISV blocked off it should run fine?
Therefore if it doesnt its elsewhere

Yes. Should run fine - idle speed needs setting as described above by jonny though. And your mixture and ignition timing would need to be correct too.

I think you need to make 100% sure there's no air leaks. Hence the suggestion of the smoke machine, which is the gold standard. Obviously its the kind of thing only  garage would have, though. Having said that, a decent engine will still run okay-ish with minor air/vacuum leaks.

okay, il try that tom morning.
Mixture and timing should both be fine - they were for 3weeks before this issue turned up >> saying that the ISV & assoc wiring was

paul_c said

I think you need to make 100% sure there's no air leaks. Hence the suggestion of the smoke machine, which is the gold standard. Obviously its the kind of thing only  garage would have, though. Having said that, a decent engine will still run okay-ish with minor air/vacuum leaks.

Its does run really nicely - just @ 3K
Il see if i can borrow a smoke machine

is your throttle definitly shutting right up to the stop? ive seen throttle cables adjusted too tight and gummy mechs stoping them closing fully.

Right what do you think of this then:
1) Tried using compressed air to pressurize the intake system and find any leaks: system seemed to hold the pressure quite well, found a few on the intake piping to the tb and some small leaks around the injectors.
Only bits not checked were the undersides of the manifold gaskets that i couldnt get to with the soapy water.

2) Took out the ISV all together and blocked off the piping: idle was smooth and stable at 1500 rpm with the idle adjustment on the tb wound right in*

3) Then put the ISV back in: idle was stable around 1500 for around 30 secs and then started to rise stopping at the usual 2500

* Surly this would suggest a leak still somewhere supplying the air

rubjonny said

is your throttle definitly shutting right up to the stop? ive seen throttle cables adjusted too tight and gummy mechs stoping them closing fully.

Yup its nice and clean and closing right upto the stop/microswitch

Now going to whip off all the intake assy and see if that helps after a good clean etc

may need a fresh oring on the idle screw?
mate of mine has his isv unplugged but fitted, never had any issues like that. he tried taking the ISV out completly and bridging the pipes, that didnt work

rubjonny said

may need a fresh oring on the idle screw?
mate of mine has his isv unplugged but fitted, never had any issues like that. he tried taking the ISV out completly and bridging the pipes, that didnt work

Just checked and it seems ok, it didnt leak when i had the system under pressure. Just tried ISV fitted but completely unplugged: idle nice and smooth at 1500 rpm > should have not bothered wiring it in  

cool, just get yourself some new injector seals and hope fully you'll be away!

could be worth a try.
Im sure i must have a bigger leak somewhere otherwise it wouldnt have run sweet and then changed to this just like that