Just filled up with tank of gas (91) and within 20 miles got check engine light. Used diametric software to read codes and have 2 fault codes

P9021:
System too rich at idle bank 2
Implausable signal

P8821:
System too rich at idle bank 1
Implausable signal

Is this a fuel problem, O2 sensor problem, air flow problem? Car is 2007 997TT

 

Could be plug problem, not burning your fuel efficiently. How many miles, flashed?

 

27K miles, Softronic flash - recently replaced plugs (about 2K miles ago).

 

Well, probably not a plug problem. Can you datalog and see how rich it is running?

 

sounds like the sensor(s) are bad.

 

Have just enabled logging. Will go for a drive and check log.

 

Why don't you give me a call as data logging and driving isn't going to diagnose an Idle trim issue. The RKAT's are what measure idle conditions and data logging above idle speed will not get the correct info. The faults should also run in as P0, P1 or P2 to start with in the DME .

An enrichment fault can show from a small intake leak as the fuel trim is exceeded for the enrichment to correct it at idle and visa versa.

Best ,
Scott

 

You can check the Maf's with the key on and then go to Actual Values and then select the Maf Sensors. A voltage reading of less than 1.1 for them would be that they are OK. Higher than 1.1 would mean it is no good.

Another check is the gas cap as if it was not fastened all the way or the seal is no good it will try to richen the car at idle to compensate for an intake leak .

A loose or not correctly put on oil fill cap causes the same issue.

These are a few common issues yet there are more that would cause an idle correction issue.

Best,
Scott

 

Erased the codes, took off and replaced gas cap and let it idled for 30 mins. Using Durametric checked MAF and O2. Everything within limits. No more faults. At moment I conclude it's the gas tank cap.

 

What plugs are you using...

 

I'm using "denko 1 step colder iridium spark plugs"

 

Great to see that it was an easy fix. Never knew a gas cap leak would cause a problem like that other than throwing a gas cap leak or evap code. Learn something every day.

 

It will be back... Next cold day, welcome it with open arms

 

Usually the gascap produces a different code, p0495 I believe.

 

it is a common problem.. you have to change the maf.. it will come back again.. you erase it and it comes back after 300km again.. i have changed 2 mafs already... i used to have problem with the right maf for over 6 months time..

(now my car has no mafs.. :-) due to 3071 turbos..)