99 VW GTI turns off when it's hot outside

I have a manual 99 Volkwagen GTI. It has been turning itself off (not really stalling bc it turns off as if I turned the key) when the weather is hot out - around 90 degrees or hotter. It doesn’t run rough or sputter - it just turns off while I’m driving. It seems to happen more in neutral or at low rpms. And it also seems to be effected by being in the sun parked - it will last longer if it’s been parked in the shade.

The temp gauge remains normal and the check engine light doesn’t come on - I scanned it and there are no codes. The dash lights stay on.

I have to wait 10-20 minutes before it will start again and then it will turn itself off again very soon, within 5-10 minutes of driving.

A mechanic recommended that I clean the throttle body - which I did but it didn’t have any effect.

Originally I thought it might be the fuel pump having issues/getting too hot but I’m thinking that would throw codes, no? And it would act like it was running out of gas before stalling?

I check some but not all ground wires and they seemed solidly in place.

I am suspecting the computer might be the issue.

Any thoughts?

Could be the things you mention above, but my guess is the crank position sensor is on the fritz. That is what tells the computer the engine is rotating so it needs to fire the spark plugs & inject fuel. when it fails (often due to heat), the computer thinks the engine is no longer running, so it doesn’t fire the spark plugs or inject fuel. Car returns to the state as if the engine stalled, key still in the “on”. If in your case car seems to be in the state with the key turned to “off”, that’s more likely an ignition switch problem.

Did you know “Sequoia” is the answer to one of the Car Talk puzzlers?

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Thanks for the reply George. You think it could be crank position sensor even though there is no check engine light or codes?

And I didn’t know about Sequoia being the answer to one of the puzzlers!

Yes. Crank sensor fault often produces no CEL or diagnostic codes. It’s a chicken and egg problem. Computer has no way to know if crank sensor stopped sending signals b/c it is not working, then engine stopped, or if engine stopped, then (good) crank sensor stopped sending signals.

I don’t know if there is a way here to search past puzzlers by keyword. If there is then you could probably find that puzzler.

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yeah, that makes sense about the chicken and the egg situation with the codes. I’ll try replacing the sensor and see if it fixes it.

Do you think the hot weather could affect it somehow? That’s one of the things that’s been tricky for me to figure out - it only happening when it’s hot.


“The Computer” is rarely the cause of many problems. Usually that’s the last ditch reason a stumped mechanic throws out when he’s ready to be done with a problem car…


Crank sensor failure can be related to heat. Hot can make it fail. Though it might start working again when it cools down.


haha - thanks ledhed - in this case it’s not a mechanic - it’s me

cool, thank you George - I appreciate the replies! I’m gonna replace the crankshaft position sensor today and I’ll come back and post results.

Although doesn’t look like we’re in for any hot days again soon, so it’ll be kind of hard to test in that way.

I haven’t found the Sequoia puzzler but if anyone reading happens upon it please put the link :evergreen_tree:

Well I’m not saying no but these are the exact same symptoms that Honda had with the fuel relay. Hot out, shuts the fuel off. Engines normally run at over 200 degrees which would be hotter than any ambient temperature, even baking in the hot sun. Only way to tell I guess is to put a fuel pressure tester on to see if pressure is lost when it stalls.


I replaced the crank position sensor - and it was no picnic to get to! Drove it around today a bit - so far so good.

I’m hoping that’s what was necessary and that’s it’s not an issue with fuel pump or fuel relay.