Porsche Enthusiasts Club Forum

Hi Guys,

sadly my Cab failed her MOT on Monday due to a worn ball joint (straightforward but not cheap) and a high CO value.

Local indie tested the car a couple of weeks back and the CO was fine (circa 2.0) - but it was 6.3 on test day.

In between I've fuelled up with Shell V-Power for the 1st time and taken her for a 200 mile blast in Wales.

Any ideas what could have caused such a change?

Hi

CO is only mixture...one screw to adjust with a gas analyser stuck up the exhaust pipe....i would have thought they would adjust it while you waited (2 mins work) unless something is blocked, like air filter etc...

If you ever get near Bournemouth I will do it for you...for free

All the best Brett

Assuming plugs & general ignition are good & the air filter is reasonable decent then it generally is Air Flow Meter or Throttle Position Switch.
The adjuster is just a trim, gives around 0.5% or so overall.

Hmmm,

thanks guys.

it needs to come down by 3.5% or more so that sounds like its beyond the scope of the adjustment screw.

Maybe worth me taking a look at the air filter.

Its just odd that its changed so much in a short time.

Perhaps best not to assume the equipment used to make both readings was not faulty or not calibrated. That sounds like a significant change in a short while so unless something broke or dropped off (surely noticeable?) then maybe one set of test equipment has a fault. I would bung another garage £10 to test the gases again before spending too much time or money on it.
Cheers
Mick

PASSED!

My local Indie (Tony Greatorex) fitted the wishbone, cleaned plugs, stripped and recalibrated the AFM and the CO is down to 1% and good for another year!

Should yield better MPG as well.

My old Triumph Stag went from failing an MOT on CO and almost on HC to passing well as soon as I changed the plugs and oil. It is surprising the difference it can make.

Need to book mine in with Tony next month heard many good things about him.

Glad its sorted!

Tony has had my car twice now, once for an oil service and belt check and now for the MOT work. He is clearly very knowledgeable with getting on for 30 yrs Porsche experience.

I asked on here if anyone knew him a couple of months back and was surprised to get no response.

I would certainly recommend him based on my experience so far.