My car has had an erratic idle problem for a while now which I've been struggling to track down. It runs quite rough when first started and the rpm dips too low and almost stalls after revving the engine or when coming to a fast stop. The idle problem also seems worse once the engine is warmed up.
I eventually got a CEL and read the following codes using Durametric:
P0171
Porsche fault code 360 - Oxygen sensing adaption idle range bank 1
P0174
Porsche fault code 361 - Oxygen sensing adaption idle range bank 2
Things seemed much better after the CEL came on but went back to running rough and erratic idle once I cleared the fault codes. The car then ran rough for the next 30ish miles before the CEL came back on again with the same codes as before. This cycle can be repeated by clearing the codes again.
I initially suspected unmetered air entering the system via a loose hose so did a boost leak test. However I pressurised the system from just behind the air box and it held pressure fine so I don't think that's the issue.
The issue also goes away if I unplug the MAF which led me to suspect that was knackered. So I replaced with a brand new one which initially seemed to help but the problem quickly returned
This has been a minor annoyance for a while but has now turned into a major problem as the car failed the MOT emissions test today with CO and HC values well over the limit and lambda of 0.947 which is just under the acceptable range. The car has been mapped and has a Speedtech exhaust with 100 cell CATs but this has been the case for the last 2 MOTs without issue so I'm sure the failure this time is related to the above problems.
Anyone got experience of similar issues or any advice on what to check next ?
I eventually got a CEL and read the following codes using Durametric:
P0171
Porsche fault code 360 - Oxygen sensing adaption idle range bank 1
P0174
Porsche fault code 361 - Oxygen sensing adaption idle range bank 2
Things seemed much better after the CEL came on but went back to running rough and erratic idle once I cleared the fault codes. The car then ran rough for the next 30ish miles before the CEL came back on again with the same codes as before. This cycle can be repeated by clearing the codes again.
I initially suspected unmetered air entering the system via a loose hose so did a boost leak test. However I pressurised the system from just behind the air box and it held pressure fine so I don't think that's the issue.
The issue also goes away if I unplug the MAF which led me to suspect that was knackered. So I replaced with a brand new one which initially seemed to help but the problem quickly returned
This has been a minor annoyance for a while but has now turned into a major problem as the car failed the MOT emissions test today with CO and HC values well over the limit and lambda of 0.947 which is just under the acceptable range. The car has been mapped and has a Speedtech exhaust with 100 cell CATs but this has been the case for the last 2 MOTs without issue so I'm sure the failure this time is related to the above problems.
Anyone got experience of similar issues or any advice on what to check next ?