Katman

A friend with a 4kq had been having a gradually worsening starting problem.

Finally came to a head this week, and he was getting a bit tired of a car that doesn't go when you want it to.

I offered to stop by yesterday and help him out with it.

First off, the starter sounder really rough, and would only crank a few turns of the motor before kicking out, if it even grabbed in the first place.

But.. It fired up pretty well on the 2nd try. It started and was running OK. Did some testing, and tried to get the idle under control.

After a few starts, it wouldn't start anymore. Thats's when the complete story surfaces:

It fires up Ok when cold even with the flakey starter, and runs reasonabley well when started. But if it's warm AT ALL, even from a few minutes running, it won't start again.

Say.. *that* sounds just like audiscott's problem! Except that he hadn't figured out a cure yet, so no help to us.

So.. Replaced the starter, so it could at least crank reliably (However, this starter had no lead to run the cold start stuff. Oh well, what to do? We put that starter in anyway!)

(Old starter's PLASTIC reduction gear assembly had broken up. Plasic gears in a starter? That's another omplete rant!)

Put the car outside, and it fired up just fine. Let it run a bit, and shut down. WOULD NOT start again..

So, messed with the coolant temp sender, both shorted and open. Still no start.

Tried powering the cold start injector with continuous 12V while cranking. If really leaving it on for a bit, the motor as almost trying to start. Tried sprayin ether, and that didn't do anything. Spark was good, but plugs were dry. Sounds like not enough much fuel..

Tried 'helping' the CIS flap open a bit more when cranking, by holding the mixture adjsuting allen key just right. Holding it 'just right', I could lift the flap a bit. Tried cranksing, and surprisingly enough, it fired up. Turned off, and cranking without helping the flap: No start. Tried lifting it again, and it started.

So, once it started again, we tried to adjust the idle back down to normal (it was up around 2500 rpm, so the motor wouldn't stall).

As we got the idle close to normal and thing quited down a bit, we could hear a vaccum leak. Messing around, we found that the funny shaped hose that connects to the manifold side of the ISV had a crack in it. So pulled that off, and taped over the crank.

While trying to get that back on, I was leaning on the big rubber cover over the cis metering flap.

Guess what comes off the CIS metering head? Yes! THe big boot! Maybe this is an "ahha!" moment?

So loosened off the clamp to the big boot, and installed it back on properly. Checked the big clamp on the throttle body, and tried starting.

Started up right away, and now will start if motor is cold OR warm, even with the cold start injector lead not connected at the starter.

Heres's what we think was going on:

-Small leak in intake (so no flap lifting when cranking)

-Cold start injector would squirt a bit of fuel, just enough to get motor to fire on first few cranks, when motor then would then start pulling enough air in to lift flap and keep running.

-When even a bit warm, could start injector wouldn't fire, vaccum leak prevents flap from lifting, so no fuel to start on.

May be not what's happening to audiscott's car, but worth a shot testing this out..?

You could try lifting the flap with the allen adjuster, but that's pretty hard to do.

Perhaps easier (don't laugh!)..

You could drill a very small hole in the boot, over the middle of the flap. (small, as you don't want a massive air leak!)

Through that hole, thread a piece of string (or thread), with a strong magnet attached to the end. Use the magnet to lift the bolt in the middle of the flap while cranking, lifting the whole flap at the same time. (Magnet won't stick to the aluminm flap)

Injectors should then spray extra fuel, and motor should start. Once it fires up, should be OK.

If that works, then I'd be looking for *any* intake leaks, as even a small leak will mess up starting.

Easy enough to fill the hole in the intake boot when done with a dab of silicon when finished.

Hopefully this is of some help? If nothing else, it shows how much even small leaks can affect the proper operation of CIS!

AudiSport4000

When my 4ktq stalled out that one night due to a boost/vac leak it wouldnt start when warm. Car fired right up when cold and ran fine, but once it got warm it stalled and wouldnt restart.
Makes perfect sense though. I told Scott to search for vac leaks, as that would make sense to me.

Good detective work

audi/s/scott

Thanks for the info, guess I need to start poking around again!

smirking

Also, verify the "flap" doesnt have any drag (up or down) would mean sticking distributor plunger