Author Topic: MK5 GTI rough acceleration and AC pressure switch.  (Read 664 times)

Offline Dobbs

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Hi folks, my MK5 GTI has suddenly started to cough and splutter under medium/hard acceleration.  I've plugged in a code reader and got the following:

A/C refrigerant high pressure switch (F118) sporadic over pressure.

I've found out how to replace the switch so will give it a go - can someone tell me why the pressure switch would limit acceleration (safety 'feature' perhaps?).

At the same time I've lost Cruise Control - would this also be related to the pressure switch?

Thanks for any and all advice  :smiley:

Offline Dobbs

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Re: MK5 GTI rough acceleration and AC pressure switch.
« Reply #1 on: 17 June 2019, 12:56 »
Additional - jut noticed that the idle is around 1200rpm, which is rather high - could there be a vacuum leak as well as a sensor problem?

There was a leak in a vacuum pipe last year which gave rough running so I'm wondering if I've actually got two problems - any thoughts?

Offline Dobbs

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Re: MK5 GTI rough acceleration and AC pressure switch.
« Reply #2 on: 24 June 2019, 10:55 »
Hey guys,

A quick update - replaced the pressure sensor at the weekend (highly recommend getting a 17mm crows-foot spanner) - it's a fiddly job, best to remove the lower engine cover, loosen the sensor with the crows foot and then unscrew from above.

And now there's a new error code/fault:  AC Pressure/Temperature sensor (G395) sporadic no signal/communication.

Unfortunately replacing the 1st sensor did not solve the missfire, so I'll investigate the 2nd sensor and see what that's all about..

To be continued  :rolleyes:

Oh yes, the idle has dropped (might be down to me wriggling vacuum pipes) and cruise control is back.

PS - booked into my local workshop next Monday just in case  :smiley:

Offline Dobbs

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Re: MK5 GTI rough acceleration and AC pressure switch.
« Reply #3 on: 27 June 2019, 07:33 »
Hi guys,

It seems like there's a period after replacing the sensor during which the system resets itself, so all is now well.  I went for a test drive immediately after replacing the sensor and the misfire was still present, but after a long drive it's now running fine.

Fingers crossed, the I is now back in my GTI!

Have a good day all.