Crasher! Help!

[billybunter]

Dear Mr Crasher, wondered if you could offer me some advice on my 2.0 8v petrol engine (fitted in a T4 caravelle as standard, but the comercial guys on the forum aren't offering any help)
It runs rich after about 2 minutes off start up, lumpy tick over, smokey exhaust, and if I try to hold it at a set RPM it drops by about 1000rpm and stutters, close the throttle and reapply it, the revs rise promptly but then die again, easy to start from cold, difficult when hot.
Replaced the air temp sender/C.O. potentiometer, coolant temp sender, plugs, leads, dizzy cap and rotor arm. checked continuity between the multi plugs on these items and the digifant unit, all ok.
Any suggestions?

[euroslap]

Try unplugging the Air Mass Meter and see if it runs any better.

[billybunter]

Hi Mr Slap, There is no air mass meter as such, just a combined CO2/Air temp meter, which makes no difference when you unplug it, same with the water temp sensor, both of which have continuity back to the Digifant unit.
Thanks for replying.

[euroslap]

Have you had a fault code read done? I was assuming they were the same metering system as a Digifant Golf, sorry. :o

[billybunter]

Hi, I haven't got that far yet, someone suggested that this version of digifant doesn't store codes! not sure how true this is, I'm restricted on time at the moment and I'm unable to take it to a garage because the MOT has run out and I need to get the rich running side of thing sorted out before I take in, If worst comes to the worst I'll have to let a garage sort it out, but I'd rather try and do it myself, I 've just bought a new oxygen sensor which I'll fit at the weekend, I don't think it's the problem because the rich running starts before the oxygen sensor gets to tempreture (that's my understanding of it anyway!).
Thanks again

[euroslap]

I'd fit the lambda sensor and see if it improves, if it's knackered the engine could be running very rich (hence the smoke). Ideally get a code read done but as you've already got the sensor change it and see if it works.

[billybunter]

Good point, that's what I'll do.
Thanks for taking the time to reply, yours is the first response I've had, nothing from the commercial section.

[euroslap]

Good Luck, hope it works. ;)

[billybunter]

Update, changed the oxygen sensor and cleaned out the idle sabiliser valve, and hey presto, much better sounding engine, still not right, but far better than it was. I think it now needs setting up by a garage, still hard to start hot, and still splutters abit if you 'punch' the throttle.
Thanks Mr Slap for your support.

[billybunter]

Hi,
Quick update, got the engine running better, but it won't start when hot, If I disconnect the Idle compenstation valve it starts straight away, and will continue to run ok whether it's plugged in or not, how ever it does make a slight difference to the sound of the engine when the lead is plug in and out, I've cleaned the valve and made sure it buzzes.
Can I run the engine without the ISV?

[gtiman]

i run my mk2 gti with the isv unplugged,partly cause i think its playing up (irratic tickover,creeps up to near on 2000rpm)partly as ive got a high lift cam so tickover will be lumpy anyway

[billybunter]

I spoke to somebody today who reakons that it shouldn't be left unplugged because it does more than just control the tick over, I haven't had time to look into this yet, I wonder if unpluggung just masks the original problem?
I've had a slight change of events, I took mine in for MOT today, worrying about it running too rich, when I went to collect it the tester said it was running very very lean, and I could qualify for zero road tax if i left it like that !!! If only! But I think this is the reason for my poor hot starting, they are going to set the CO tomorrow, and then we'll know.
Thanks for the reply.

[billybunter]

Managed to get an MOT today, and they adjusted the CO, but when it came to driving it home, it was running like a pile of poo, so bad that I had to pull over and do a quick digifant tune up by ear, took a chance and pulled into the petrol station to get some juice, popped the bonnet, knowing that I'll have to disconnect the ISV to restart it, put some juice in, and it restarted with out disconnecting the ISV, so it looks like I may have stumbled across the right CO setting!