Corrado VR6 knocking on idle and misfire

[Chaz! 10]

Bit of a weird one, I've got a '92 Corrado VR6 and today I had a few its to do to it, the idle has been hunting/ rough a bit recently, and the clutch slave cylinder had gone so I cleaned out the ISV and replaced the slave cylinder and changed the gearbox oil while I was there. Once it was back together I started the car and was going to go for a test drive when I realised it wasn't running right and was making an odd clunking sound and the exhaust was popping more than usual.

 

It can be driven but tries to cut out when the revs drop and has a definite misfire and is way down on power. If anyone has any ideas what to check I'd appreciate it cos I really can't think whats gone wrong. Here's a video of it idling and clunking and a video of it revving up and popping

 

 

 

Cheers for any help!

[BrettS 10]

Only yesterday after first cleaning my idle control, the revs hunted like crazy and would drop of to the point of cutting out and clunk as the revs tried to pick back up. I took of the valve and cleaned it back up with wd40 and air line. Refuted it and idled fine after that. Started sticking again this morning for a while and rectified itself. I'm assuming the valve it's self is sticking, after cleaning it's either cleaned out any lubricant it had, or there's some residue still within the valve. A new valve is required as without being able to strip the part down I don't think you will ever clean it properly. Try cleaning it again with wd40 and see if there's any improvement. Wd40 does disperse with the heat ect so wouldnt pose a huge risk to the engine.

[BrettS 10]

Also check the lead are seated correctly

[easypops 8]

And check you have the leads on the correct part of the coil, it'll still run if you swap one over, just not very well, and yes, I have experienced this :lol:

[Chaz! 10]

Okay guys thanks for that, I'll check all the HT's take the ISV off and clean it again and blow through with an air line, maybe leave it to soak overnight or something, does it need lubricating again after its been cleaned?

[BrettS 10]

Okay guys thanks for that, I'll check all the HT's take the ISV off and clean it again and blow through with an air line, maybe leave it to soak overnight or something, does it need lubricating again after its been cleaned?

I assume there would be a degree of lubrication as it is a moving part. I just wouldn't want it soaked in the stuff as it would eventually clog up again. But if it works then at least you have identified the fault. I'm going to order a pattern part from ebay. They are cheap enough and with the millage I do, it should be fine

[Chaz! 10]

Yeah that's true, i'm thinking soak it in carb cleaner overnight and lubricate it with a little dry lube or something. I didn't look for patterns, had a look at heritage and saw the mk2 one was like £300 though :|

[BrettS 10]

Yeah that's true, i'm thinking soak it in carb cleaner overnight and lubricate it with a little dry lube or something. I didn't look for patterns, had a look at heritage and saw the mk2 one was like £300 though :|

 

http://pages.ebay.com/link/?nav=item.view&alt=web&id=321619923810

I have ordered one of these. Part number is the same as a vr6 one and at that price you would need a lot to fail to make the heritage one worth while

[fla 9]

As above check the leads are correct but also remove the plugs to see they're not clogged up.

[Chaz! 10]

Yeah will check all the plugs and leads and maybe pick up a pattern ISV just to eliminate that as causing the problem. Cheers guys, I'll let you know how I get on

[Chaz! 10]

Update: I have now changed the plugs (they were absolutely ruined, some of the worst i've ever seen), the coil pack, and the ISV for a new one, the car will now start only if you give it throttle, and you can hold the throttle to keep it running, backing it off to around 1200rpm and you can hold it there on the gas but as soon as you let go it will cut out, the exhaust is still popping as well so I guess the mixture is still off.

 

I'm sort of clutching at straws now, next things I can think of are MAF, lambda and temp sensor. After that I'm pretty much out of ideas, although I was reading on vortex someone was saying that cleaning the ISV wrong can result in shorting out the idle control part of the ECU so maybe that could be something to do with it.

 

Anyone have any other ideas?

[BrettS 10]

I have had the same issue over the last few days and I have finally found a resolve to it. Like you I cleaned out the idle control and in the end replaced it with a patten part. Now the issue still arouse with hunting at sort of idle to boot. Now cleaned the isv again and still the same issue as well as a strong smell of fuel. Popped the bonnet up and found a fuel leak from the joint to the injector rail, but concerning as it was dropping fuel on the alternator . Replaced the fuel clamp and also found the afm plug had come out or I had left it unplugged. So re connected that and run fine but still hunting, replaced the new pattern isv with the cleaned Bosch one and boom. Running superb idles perfect, no smell of fuel and starts and idle fine and doesn't cut out. The cutting out on start up I put down to the maf un plugged and the fuel line draing itself of fuel in the line. The dodgey idle down to the fuel line drawing air and the new idle control valve

Edited February 7, 2015 by BrettS

[Chaz! 10]

Interesting, glad yours is sorted now, I'll check over all the fuel lines and soak my ISV overnight and then swap it for the pattern one to see if that helps, and I'll have a look over the fuel lines as it does seem like a fuel/air problem due to the popping exhaust. I'll let you know how it goes

[fla 9]

Sounds like an air leak somewhere. Can you get it on vagcom to check for fault codes and trim errors?

[Chaz! 10]

I'll try spraying a bit of carb cleaner around the hoses to see if the revs pick up but its tricky as it won't idle. Not sure if I can VAGCOM it as its early and doesn't have a port for it