Quick help! 2.5 losing power

Sup guys... here's the quick story.
2.5 Stock MK6 with 112k miles losing power driving down to LA from SF

All services done, engine, trans.

Right about the Grapevine a the top of the hill it started to loss power after a great starting of the trip.
80mph are pretty normal up there and it was 100 degrees outside.

I had to pull over on a rest area since I couldn't keep up driving 50mph.

No lights on the dashboard ever. Got out turned it off and did a restroom trip and got back in the road like nothing happened.

What could it be. I'm afraid that this will happen in the way back.

Thx in advance.


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Since you're climbing hills and 100 degrees F. I think it maybe knock related or vapor related or a combination. I read an old thread where the 2.5 ECU will dial the ignition timing back (retard) the timing by a significant amount when knock is detected. In that case it takes a long time for the ECU to normalize maybe in a protective mode, by turning off it resets the ECU.

It could be vapor lock, especially if your using a gas with ethanol.
https://en.m.wikipedia.org/wiki/Vapor_lock

If you're not using 91 octane you should get some or use a fuel with no ethanol.

Good luck

MLue1 said:

Since you're climbing hills and 100 degrees F. I think it maybe knock related or vapor related or a combination. I read an old thread where the 2.5 ECU will dial the ignition timing back (retard) the timing by a significant amount when knock is detected. In that case it takes a long time for the ECU to normalize maybe in a protective mode, by turning off it resets the ECU.

It could be vapor lock, especially if your using a gas with ethanol.
https://en.m.wikipedia.org/wiki/Vapor_lock

If you're not using 91 octane you should get some or use a fuel with no ethanol.

Good luck

Click to expand...

Thx for the help...

Car behaved normal after that and showed no problems since even in the way back... it was not as hot tho.

It could be the fuel since i haven't been driving the car ok the and my wife or my sister share it sometimes so they're responsible for the kind of gas pumped. I will ask.

Thx again.


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Thanks for closing this off properly! Under extreme conditions it maybe a good idea to use a higher octane gas.



Here is a list of past Threads on Ignition Timing and Octane:

http://www.golfmk6.com/forums/showthread.php?t=27757&highlight=ignition+timing

http://www.superstreetonline.com/how-to/engine/epcp-1007-2010-volkwagen-jetta-proven/

http://www.golfmk6.com/forums/showthread.php?t=44465&highlight=ignition+timing