91 GT 16v stalling when warm

[andypc]

TIA to anyone who can help.

Cold morning, starts straight up, revs go up to 2k fine then settle at 900.

Drive away, revs are perfect when in gear.

Engine warm, come to a junction, drop the clutch, the revs just fall to zero and it cuts out.

As a test I dropped the clutch at 4k revs doing 90 down the motorway. The same happened, the revs just zero'd.

Please help i just spent £500 quid on this old darlin and now she's doing this to me!!

[boschmann]

Are you saying you were at highway speed @ 4000 rpm let out the clutch & the engine just stopped dead? Or, was it just the tach? Hopefully it was only the tach. I'd worry about the coil (very common to fail), perhaps the ignition module.

[andypc]

Yes it literally stops dead but has no other symptoms! Pretty sure the tach is fine as it seems to match how fast the shaft should be rotating.

I notice also that when i drop the clutch @ 4000rpm the revs fall a lot faster than they should.

[boschmann]

Yes which stops dead? It can't be the engine. Your losing your spark which is stopping the tach.

[andypc]

Thanks but i'm not sure. It's been fine since new plugs a year ago, then started happening. Brand new plugs last week made no difference. The HT leads seem fine too. Any ideas?

[boschmann]

Ignition coil or module.

[andypc]

But it's not misfiring and is perfect until it needs to idle. The injector just doesn't kick in when the throttle's off to make it idle.

[boschmann]

What do you mean by dropped the clutch? If you push the pedal in & the engine stalls, that's something completely different.

[andypc]

Yes just push the pedal in to disengage the gears, or neutral would do the same i guess.

Sometimes it idles fine, but usually seems to forget to idle when the engine's warm.

[boschmann]

Dropping the clutch here means to let it out rapidly while in gear, as in doing a burnout or chirping the tires. That had me confused. Basically the engine is just stalling. The easiest first looks are at the filters & cleaning of the throttle valve with throttle body cleaner & a toothbrush. Just pull off the air intake boot, open the valve & clean it all out.

[andypc]

Ahh soz for the confusion! Thanks I'll try cleaning those out next.

[spasticone]

My passat 16v was doing almost the exact same thing. I have a few posts on it. I messed with everything and then finally threw in a new O2 and the problem was gone. If you wanna try it an 87ish mustang lx 4cyl o2 is the same 3 wire sensor with a dif. plug and cost 35 compared to 100 buck. Just chop the plugs, solder, and seal with good shrink tubing. Hope this helps you out.

[andypc]

Cheers man helpful! hopefully it won't be that but if it is uv saved me some money

[Glenn101]

Similar problem was the power stage, book gives no check for the power stage itself only the signal and wiring from computer.