Keep timing from changing and keep it set to where it is set?

The valve body in the transmission is bad

Don't know if this will help or not. I had a 1991 Camry that ran fine until it got warm. Would sputter and stall. I cleaned and messed with the throttle body adjustment until it ran OK. Can't remember what I did but there was some sort of adjustment on the throttle body. Good luck.

I had this problem on my 02 s60 after messing with the battery. The problem is that the computer is stupid and "forgets" how to manage the car if it completely loses power.

To retrain it you basically just drive the car. I've seen several sets of instructions but here's what works for me:

1. Start the car and let it idle until warmed up.
2. Using moderate throttle (don't floor it) get the car up to highway speeds.
3. Slow down to a complete stop.
4. Repeat 2-3 a few times if you're so inclined.
5. Done!

Skipping the highway part will work too, however, I've heard it can take much longer to retrain the computer (weeks to months depending on driving habits.)

U could be run on eco a/c where the engine is using the power until it has extra to spare. Warm at start could be simlarly that there is now cold air yet and has to "make" cold air to distribute when ready. See if u can find a setting for reg use. cheers, ps eco saves dollars/euros.

Double check the timing. If the timing is dead on when it starts and it runs fine that is ok. If the timing is off when it is warm then the vacuum advance is faulty or there is a vacuum leak that only occurs once everything has opened up and the motor is warm. When you set timing on these vehicles there is usually a vacuum line that runs to the Distributor assembly that needs to be plugged when setting timing. This is because it off sets the advance when setting timing. When the engine warms up the Advance opens to advance the timing to maintain time with the motor as it rev's. The higher the RPM the more vacuum that is applied to the timing in order to keep everything clear and keep things from making contact that aren't supposed to.

the choke is sticking. lube all linkages and run a fuel system flush through the fuel system

Ok, time for car school. The vehicle is operated by the computer, every electrical concept that is. When the engine is cold, it starts fine because the computer has placed it in "cold start mode", putting more fuel into the engine than normally would until Once the engine is warmed up, a temperature sending unit or temp sensor tells the computer to change to normal run mode. IF said temp sensor is faulty and is not telling the computer to make said change, it stays in cold start mode, still dumping excess fuel in the engine that is now not required, cause it's warmed up. Like keeping the choke closed on older vehicles. Now I think you can answer your own question, when this no start action is happening after warm up and it always starts fine when cold, what's the first thing you check ? Right, the unsuspected temp sensor. Change that and no more start problem. Have a wonderful day. Glad I could be of service.

I would suspect fautly spark plugs.

Clean the choke and linkage around the air cleaner again.

You are on the right track.

I will give ALL the intake manifold bolts a 1/6 turn....just to rule out leaky intake manifold gasket.

Check for loose or leaky vacuum hose.

Since you truck is 1987. I will replace all small vacuum hoses.

Change one at at time.

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Change the fuel filter
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Test fuel pressure
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Check the ohm specification on the coil.
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If the wires are over 3 years old then replace it
Check and clean contacts
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Make sure the wires are not cross.
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Do a good carb. cleaning and use Chevron gas for one tank full. Do some high RPM highway ran and see does it improve.

First off need to know if it is a 2.0 or 1.8T engine. Most likely you have a 2.0L engine. The coolant light on the dash will stay blue untill the temp reaches a set temp by ECM, then goes out. Since the Beetles do not have a temp gauge you dont know what the actual temperature is. I replace thermostats on these all the time for this problem on these cars. To test this, start car and let run at idle and set heater fan on low. Let run untill you feel warm to hot air coming out the vents. Once its as warm as it is going to get, go drive the car at a steady cruise and see if the temp drops. If so then you need a thermostat replacement. I only use OE VW thermostats 050121113C. Hope that helps you out. Kevin