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Matt, Engineer - BEng Hons
Category: Porsche
Satisfied Customers: 21106
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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Porscheoccasionally fails to engage a gear when

Customer Question

Porsche(###) ###-####occasionally fails to engage a gear when accelerating, this usually happens when starting off in 2nd second gear. I tried pushing the SPORT button and this worked the first couple of times but now makes little difference.
Submitted: 1 year ago.
Category: Porsche
Expert:  Matt replied 1 year ago.


I'm assuming that this is the tiptronic transmission ? do you have any error messages or fualt lights on the dash?

when was the car last serviced? and how many miles are on it?

Customer: replied 1 year ago.
it is tiptronic. No error messages. 75,000 miles. Serviced 3 weeks ago which included new spark plugs and oil change.
Drove 30 miles today and no problem.....strange!!!
Expert:  Matt replied 1 year ago.


Ok the transmission will stick in 2nd if it thinks there's a problem, so I'd suggest the next step is to get the car plugged into a Porsche diagnostic device to read off any fault codes and check if all the sensors are reading correctly

if the transmission fluid hasn't been rpelaced then I'd say that should be the next step as old / dirty fluid has a strong effect on transmission performance

Expert:  Matt replied 1 year ago.


do you still need help?

Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash iss plit between the site and the expert. so if my answers have been helpful please rate my answer.

Customer: replied 1 year ago.
Sorry but answer doesn't really help. I called the garage and they didn't see any fault codes when they recently serviced the car. They tell me that its not due for transmission fluid change until 120,000. Problem happened again yesterday, I stopped at a stop sign then made a left turn in automatic 2nd gear and nothing happened, the car limped along with no acceleration, put it in neutral and still no acceleration, then back into automatic drive and no acceleration, then tried changing gear with tiptronic and still nothing, then a few seconds later it started to engage the gear and accelerate. I told the garage, they have no idea why and said to bring in, but at $75 an hour I would like to give them a clue as to what is wrong. Hope you have some good ideas what they should check for.
Many thanks
Expert:  Matt replied 1 year ago.

Hello Alan

OK this sounds like you might have an internal issue with the transmisson as there's a fault that can crop up with the ZF4HP22 unit

this image details a comon problem with the forward clutch

and if this is the case the transmisson will have to be removed and stripped down

sorry its not better news