Dodgy starting idle

Last weekend my mk2 valver had to be jump started for one reason or another. Anyways, since then the idle has been rather high at around 1000-1100rpm depending on how cold it is. Would the battery dying have rest something in the ecu or has the air\fuel mixture been affcted in some way?
Want to get this sorted as its quite annoying sat at lights with the car seemingly roaring away
Edited by: Mark16v

 

The ECU on a 16V only controls ignition and has no volatile memory, so no the battery thing couldn't have effected anything.

 

Oh right... Puts a spanner in the works with that plan. Reckon that the ISV needs cleaning then? Does seem to wonder down to an almost stalling point occasinally when its first start and drive for 2 minutes

 

Check the 3 temp senders on the end of the head.

 

Right, I didn't have a chance to check the senders at the weekend but it seems to have got a bit worse. When its starts from cold (any time of the day) then the engine revs slowly up to 2.5k rpm and falls to between 1.5 - 2k. Idles here even when I rev the engine [:^(]
Drive 20 metres down the road in as high a gear as poss to force the revs down and it has no effect but then 2 minutes down the road it idles constantly at 1k - 1.5k. I've checked the ISV which buzzes when the ignition is on and all the pipes are connected properly. Did see the pipe coming from the underside of the airbox wasn't completely connected so I plugged that all back together which made no difference.
Another thing which worries me is the air box seems to have a bit of oil\water settling on the top. From looking about it comes from one of the larger pipes which plugs into the airbox. I'm quite worried that its something major as my head gasket went a few months ago and I couldn't afford to get it repaired again if its anything nearly as expensive!

 

Dont worry about the crap on top of the airbox, the breather hose pumps all kind of rubbish into the air filter, particularly in this cold weather.

Check that the cold start injector isn't running for too long. This is controlled by the thermo time switch which is the large brown sender in the end of the head. This feeds the cold start injector in the end of the inlet manifold (has a blue plug on it). The injector should only be feed with voltage for between 2 to 8 seconds depending on the temperature. Check it's not running for longer dumping extra fuel in.

 

Cheers for the tip Golden, I really wanna sort this altho my girlfriend seems to think the cars fine! She sat and asked why it was so loud when I started it this morning. Her reasoning was that it was just cold so the poor thing is trying to warm up a bit....

 

2 things that havent been mentioned fully...


check really carefully for vacuum leaks or loose vacuum hoses.. esp the one that comes out of the block as it sometimes gets hot and cracks over time.. the idle not falling back again consistently is often due to this.


findnig vacuum leaks isnt easy.. you just have to feel your way along all the vacuum hoses and see if you can feel a leak. some people suggest spraying wd40 all over the place and seeing if the enginer stutters but i've never had success with that method.


and also.. although you've mentioned you checked the ISV is buzzing.. but you may find giving it a clean/flush outhelps a hell of a lot too. its a really simple job and can be done in 10 mins.

 

Just to confirm, the ISV is flushed with petrol yes?

 

Did I read somewhere that it is best done leaving the ISV in petrol and leaving it energised for a period of time ?


If so is it a pulsed feed or does it just have a constant 14.8V feed ? If that is that case I can run it up on my old CB 14V bench PSU and leave it in petrol for a good few hours.

 

yes you can flush it with petrol.. there is a guide on this forum somewhere that describes soaking it that way.


the guide on here doesnt mention connecting it up to leave it open.. but i have seen a guide someone else that does (i think on a 'rocco or corrado site)


personally i've had good results with a can of carb cleaner.. just block one end with a rag.. squirt loads in and give it a good shaking.. i used a cut off lemonade bottle to collect the deposits so i could tell when its clean.


i have no idea about the voltage apart from that an ISV has 12V written on it.

 

I'm still experiencing this problem which is really annoying.
Friday afternoon I disconnected the ISV and soaked it in carb cleaner for an hour or so. Disconnected all of the wires from the coil and plugged them back in after fiddling with em for a bit. ISV went back on, checked and it buzzed fine. Tried starting the car and it started to idle correctly. Revs went up to 2,000rpm and then dropped down to around 850. Blipped the throttle but each time the revs dropped it nearly stalled. Had a look and it turns out the green wire going to the cold start valve connector is broken.
Thought I'd cracked it but the following morning (car sat for around 9 hours so was as cold as it was gonna be) it did the usual rev to 3,000 and then settled at 2,000.
The ISV doesn't seem to come on all the while, would the feed from the air box affect this? The elbow joints aren't as tight as they should be and the pipe is caked in crap. Wondering if this would affect it?

Also not sure how to check the ISV control box, is there a guide? Had a look but couldn't find one. Would the temperature sends on the head tell the ISV not to come on?
Edited by: Mark16v

 

lol Just disconnected the ISV and went for a drive, revs drop correctly when the throttle is released and the idle is a constant 1,000rpm Problem is definately in the ISV circuit.

When i first started it with the ISV diconnected the engine wanted to stall a few times but I'm guessing this is cause it was cold, once up to temp it was spot on.

Gonna try pinpointing it to see if I can fix it, don't fancy holding my foot on the accelerator every morning at junctions etc

 

Don't think the ISV is at fault since there's an under lying problem of it not always being on. The idle is already raised a bit I think as when I just parked up I was able to cruise round the car park in 2nd gear without touching the accelerator

 

You're so kind

Only problem is my ISV doesn't always run so I've tried this method about 2 times with no luck. Can't even try GVK's guide since the ISV is supect (or at least the control module is anyways)