Hesitation

[wizard263789]

Hi,

I have a 2007 987S which is slightly hesitant especially when cold.

I have used a Durametric tester and there a no fault codes shown. However, using 'actual values' when driving the tester is picking up odd random misfires (no specific cylinder or pattern) and the air intake temp is reading 30C whilst the outside temp is 13C.

Can anyone shed some light on whether the odd misfires are 'normal' or what a normal air intake reading is given the outside temp. Any information would be useful before I take the car to the dealer (in fact any information would know doubt assist the dealer)?

Thanks.

Edited April 19, 2008 by wizard263789

[paulv]

Hi,

I have a 2007 987S which is slightly hesitant especially when cold.

I have used a Durametric tester and there a no fault codes shown. However, using 'actual values' when driving the tester is picking up odd random misfires (no specific cylinder or pattern) and the air intake temp is reading 30C whilst the outside temp is 13C.

Can anyone shed some light on whether the odd misfires are 'normal' or what a normal air intake reading is given the outside temp. Any information would be useful before I take the car to the dealer (in fact any information would know doubt assist the dealer)?

Thanks.

Hi Wizard,

First, congrats on the 07 Colbalt Blue Boxster -- same color as mine!

I also have a Durametric tester and last August I ran a test tracking the engine compartment temp, engine temp, and oil temp. I did this for 10 mins from a could startup and never exceeded 2500 rpms while driving. I did this because I mainly wanted to see when the engine/oil temps were the same.

I did see that the engine comp temp averaged around 30C during this time, so that's probably why you saw the same value for air intake temp -- the air is probably being heated up by its surroundings.

Once in a great while, I get a quick misfire and thought that this may be due to the ethanol in the gas but I haven't proved it. I just bought an ethanol tester to check the gas on my next fillup.

Do you have any other info on what Durametrics saw for misfires -- did you log the values into a file, etc? Did it happen shortly after startup, during driving, etc?

Regards,

paul...

[White987S]

wizard263789, do you have any engine or exhaust modifications? What type (octane) of fuel are you running? Manual or tip tranny?

[wizard263789]

Logged data to file. Logged engine temp, speed, air intake temp, and cylinder misfires.

Misfires occur during driving no pattern with regard to speed etc or to which cylinder the misfire occurs. Normally, one or two misfires are detected occasionally and within the given sensor period. 10 minutes drive will result in 20 - 40 misfires being detected. I.e. Not very many considering the number of times each cylinder will fire in that period.

Fuel is standard premium unleaded which in the UK is octane 97.

No mods on the car except the Porsche sports exhaust and the misfires occur whether the valves are open or closed.

I could live with the misfires if the car didn't feel hesitant but in fact I only ran the diagnosis and found the misfires because it was hesitant.

[White987S]

Check the spark plug wires.