lambda - Page 1 - Boxster/Cayman - PistonHeads UK

hi all, my 2.5 986 failed its mot on lambda 1.030 but no fault codes are showing I`ve bought a new lambda sensor but witch one should I change first help please artdon

Is the Lambda sensor faulty? I doubt it just of an emissions report. Playing parts darts is likely to work out more expensive than getting the fault diagnosed correctly. Did the MOT tester get the car hot enough as 1.030 is only just a fail?

hi thanks for your reply yes the car was hot and he tried several times but could not get it to pass al other readings were fine

It would be best to find someone with a scope to test lambda sensors if one isn't working this will show it up.

IIRC that model year just has 2 lambda (O2) sensors, one ahead of each converter. I'd say if one sensor needed replacing that you should just replace both. However, with no error codes pointing to a sensor I think replacing them is perhaps premature. I just had my 02 Boxster (with 279K miles) emission tested and it failed. Really. And each Porsche senior tech responded to the news with a "Really?". Oh, the HC (hydrocarbon) reading was high. Failing limit was a reading of say 49 and the reading was 50. Both techs told me that with no error code and with all readiness monitors set to complete -- they were -- to just take the car out for a longish highway drive. While I had driven the car around town and gotten it fully up to temperature, including/especially the converters, both said the car needed to get out on the highway and really be driven. I headed out and after around 50 miles was back at the testing shop and had the car tested again. This time the car passed with no problems. The HC readings were less than half as high as they were before. Say the reading was 20 vs. the failing reading of 50. So, based on my very recent experience my advice is you might want to take the car on a nice long (~50 mile) drive. No need to get all crazy with the car but try to drive at a steady but legal high speed for say 20 to 25 miles then quickly turn around and drive back driving the car the same way. You want to pick a route and a time you can keep the speed at the legal speed and at a steady speed. Avoid stop and go situations. It might not be a bad idea to fill up the tank with fresh gasoline of the proper octane grade before you head out. Or drive the car around enough to run the tank down so there is room to add fresh gasoline.

hi all ,just been for a mot re-test changed two clamps on silencer then it passed thanks all for your input

Result.

Good that it was nothing serious. How'd the exhaust clamps get loose? Has someone been at the exhaust?

To be honest with a lambda of 1.03 it was likely to be an exhaust leak post lambda.

Rockster said: Good that it was nothing serious. How'd the exhaust clamps get loose? Has someone been at the exhaust? UK climate and local authority measures to keep roads clear of ice/snow (when we have it) mean exhaust fixings on P cars last about 2 yrs at best (I'm yet to do a 997.2 plug change without having to resort to oxy/acetylene and replacement of the exhaust fixings) We essentially drive round in salt water solution for 3-4 months of the year. It was an eye opener seeing a 8yr old car imported from the US with 100k on it - no corrosion whatsoever on the engine cases / exhaust or wheelbolts (full history and original parts from new.......)

Ah yes, I should have remembered. I tend to forget not everyone enjoys months and months of dry weather with no snow or ice in the winter, just rain, and some winters not much rain either. My '02 Boxster is on the rack awaiting a rear bumper cover respray -- someone ran into the back of the car at a stop light the other day -- and new exhaust manifolds. The stock ones were unharmed -- the damage was confined to the bumper cover paint thank goodness -- but I bought a pair of used ones with probably fewer miles. The stock ones have nearly 280K miles on them and the left one is rattling. Anyhow, if I posted a picture of the underside you would not believe the car is 12 years old and has as many miles on it as it does. The hardware underneath looks while not factory fresh relatively unfazed by the years and miles.