1987 GTI 16V Won't Stay running

How enthusiastically is it turning over? How does the fuel pump sound when you turn the key to the on position?

John,

Thanks for your response.

The engine cranks strong and the fuel pump is running.

The starting problem was due to a faulty thermo-time switch.

The idling problem remains. When engine is cold it will idle for 45 - 60 sec. and then die. If the idle speed screw is opened way up and then screwed in after the engine starts, the engine dies at about 1,500 RPM.

The resistance on the temperature sensor checks OK (2500 ohm) when the engine is cool. Also, the idle air stabilizer valve has been swapped with one from another car with no help.

Any ideas are welcome.

Regards,

Sounds like a significant vacuum leak, remove CIS-e air boot to check for cracks, check all vacuum hoses for leaks, including the one at the knock sensor/ignition control unit, located under the water tray behind the master cylinder.

Thanks!

I am now on to something as when I hooked a vacuum gauge on to the main vacuum line, it read 0 vacuum. Now, to find the leak.

Regards, Wayne

I agree with Regal953.....check for vacuum leaks.....maybe even brake booster. I can usually hear the larger leaks when the engine is running.

Also check the fuel distributor flap to make sure that is it adjusted properly.

Did you check the current going to the fuel pressure regulator with a DVOM hooked in series? Ignition timing good? Spark strong?

Switches working on the Throttle Body?

All of the vacuum lines except for the line going to the module on the passenger side of the cowl were bypassed. The module under the ignition module does not have a vacuum line. Engine runs much smoother, but when it warms up, it won't idle below 1,500 without dying.

How does one check the brake booster for vacuum leaks?

Again, thanks to all

Wayne

You can unplug the brake booster vacuum hose and plug the port at the intake manifold.

When you said the vacuum was '0', was the engine running and did you connect it to a port that should be getting vacuum with the throttle closed?

"Wayne Faas" wrote snip

All,

Found the culprit, the boot on the air flow sensor had a big crack on the bottom side of the bellows. Replaced the boot and all is fine.

Thanks to everyone for their help.

Regards, Wayne

congrats!

I think Regal953 nailed your problem quickly! ;-)

"Wayne Faas" wrote

snip

This is how a vacuum brake booster is checked. Step on brake pedal several times with engine off until brake pedal turns hard, hold pedal down and start engine: Pedal must move down under foot/ vacuum assist if booster is OK.

AFAIK That does not accurately check for "leaks", it only checks to see if the booster can function. I have seen booster with bad seals under the master cylinder and also with bad check valves or hoses. Now if you said the you started the engine and shut it off and heard hissing from the pedal area or booster....................then that sounds like a problem. ;-)

He doesn't have a braking assist problem, he is looking for a vacuum leak. For what he is facing it should suffice. I worked for Porsche Audi dealers as an A tech for 25 years, I should know a few tricks by now, shouldn't I?. I want to help the guy find the problem. Don't worry about me, just give him the solution... ;-) As far as hoses and check valves, I would've checked those first before blaming the booster, wouldn't you? And bad seals are largely the result of a poor installation, not material failure, aren,t they? Thanks for the input anyway.

I welcome your understanding! ;-)