Why does it stall ?

[Jonathan]

Fired up the quatro....errr GT2 today for some tests.

Still has the start, run for 2-3mins, struggle, splutter, stall, re-start, splutter, stall, re-start, splutter, run like a peach - effect on it.

Haven't been too fussed about this but I want to try and get it sorted - checked on freescan and the A:F ratio is a bit erratic (GT3 is solid) as low as 10 and as high as 18 !

Once it's warmed up slightly it runs really nice actually but not sure why it's lumpy as hell to start with. Tested all the sensors and nothing is at fault from what I can see, everything is reporting as it should be.

Need to take a new data file (notice how I avoided saying log there) of the engine parameters but I must admit I am a tad stumped to what is causing this to play up when everything seems to be working absolutly fine.

I do have the charcoal canister disconnected at the moment but this has been a prob with the car from day 1 so it's nothing I have introduced......honest

[Vulcan Grey]

Check your IAC counts when fully warm at idle.

Should be between ~15-40 or 20-40 in Freescan.

If it is above that, it can lead to stalling problems after starting the car from cold. Also can make it stall the moment you touch the throttle the frist time.

There is an IAC setting procedure in the EMH section of the manual. It involves adjusting the minimum air rate bleed screw while watching the IAC counts in freescan.

I bet that is your problem...

Either that or an air leak in the manifold.

[Jonathan]

Cheers for that, the IACV seems to be cracked although I did take it off and it seems to work. Seems to be about the same as my GT3 though ~ 60-80 starting from 170 as the Freescan manual says.

Annoyingly enough the MAP reading at idle is ~ 0.47 as well which is inconveniant lol.

I'll give it a go at resetting the IAC tomorrow, weather permitting - and take another scan and try to pin points exactly where the probem is.

[Paul C]

Two things have caused this on mine. The IAC as mentioned, and there's this tiny black air

hose that connects just under the chargecooler (so small it looks like a wire), this came off

mine and it idled then stalled.

[Jonathan]

OK what about the sparking plug leads ?

I had a look today becuase the leads are just flapping in the breeze inside the bay so I re-routed them correctly (and away from the timing belt !)

From front of the car to back my formation was :

4,3,2,1 on the engine

4,1,3,2 on the coil packs

Looked at the GT3 and the engine side is reversed, 1 is at the front and 4 at the back....wonder if that wouldn't help for starters (although I think not).

Haven't been able to do anything today as the comunial starter motor is on the GT3 (GT2 gets it saturdays, GT3 sundays....you think I'm joking !)

[Vulcan Grey]

Switching 1-4 or 2-3 doesn't matter since the coil packs are wasted spark. Both 1&4 fire at the same time every time, also 2&3 both fire together.

Like Paul C said, also look for air leaks, you may need to pull the chargecooler box off it's mounts and disconnect the grounding strap to pivot it out of the way so you can inspect all the hoses that connect to the head. Don't forget the line at the front of the engine near the water pump that takes air and gas vapor from the charcoal cannister. You might also note the orientatin of the one-way valves and check their operation.

The throttle butterfly adjusting screw should never be adjusted! That's the one that balances the butterflies. But some previous owners might have.

The minimum air rate bleed screw should never need adjusting, but I've seen several cars that either had it adjusted by a PO, by ear, or there were air leaks that had to be adjusted.

Bad spark plug wires can cause the car to falter under load, they usually idle ok.

You can test each cylinder this way.

Start the car, and let it idle.

remove the electrical connection to the IAC.

and then pull off one spark plug lead at a time. The rpm should drop the same for each cylinder. If not, then you have a cylinder that isn't running correctly, could be spark or injector though.

[Jonathan]

OK managed to take a log of the thing today after new starter fitted.

Started off really nicely - then gets really lumpy whuch you can see from the RPM reading (this is accurate). End of the log the car was running smoother as it does when it gets warm, it seems to require a small blat from the throttle (seen on log) to get it to behave though...

O2 sensors seems to be operating correctly, although the IACV seems to be moving in and out (this does settle down) - MAP is ok, A:F - is this right ?

Load looks wrong to me, esp sinne it's just sat there, I also notice the alternator isn't excited but that was working fine 7 months ago so it's probably something silly.

Any clues ?

One thing, it didn't stall this time, just went lumpy - it's not a huge issue, although I don't think I'd be able to turn the key and just go, just bugging me really.

gt2.csv

gt2.xls

Edited May 3, 2008 by Jonathan

[Qavion]

and there's this tiny black air

hose that connects just under the chargecooler (so small it looks like a wire), this came off

mine and it idled then stalled.

Same on mine a few years ago, but this will generate a Check Engine Light and Freescan will point directly to the pipe

re the charcoal cannister... Did you block the pipe going to the manifold when you removed it? The manual mentions that the evaporative emission control system could cause problems with idle, but I'm not sure if this is because there is too much air getting into the intake manifold... or too much fuel vapour from the tank? Anyway, when I was playing with my emission control plumbing, the black and white check valve (between the front of the engine and the cabin bulkhead) came adrift from the pipes. This would create an air leak in the manifold. Make sure this hasn't fallen off.

Cheers.

Ian.

[Vulcan Grey]

Jonathan,

I'n your Excel file, your coolant temp never gets up to fully warm. You'll need to redo a run from start and let it idle till warm ~80C. Then we should see what your IAC is when the car is idling when warmed up.

Otherwise, I took a quick scan and everything looks fine, except your battey V is very low.

[Jonathan]

Yeah, I had to fire the guy who forgot to re-connect the alternator cable back to the starter motor post....

All sorted now (can't get the staff these days....)

At warm temps it's perfect, sits there and glugs away, drives fine as well - it's only from cold it has a problem.

I have some old data (last year) attached - I'm not 100% sure this can be cured you know, might be something I have to live with...

Edited May 5, 2008 by Jonathan

[Vulcan Grey]

Yeah, that data is crap too.

Your TPS keeps showing 2% and the engine is running at 2800rpm, then at 0% TPS you are at the desired 986RPM, but you show a 5% engine load, and your IAC is at 5, which is too low.

From what I have seem from your more recent data, the IAC looks like it will end up being high, which would cause the cold stalling.

Anyways, keep looking for air leaks, and get some data from start-warm up at idle.