Hi, I have a problem with my 2002 XKR that was a project and I just reassembled everything. Getting codes 171 & 174 & 1000. I have replaced all the vacuum lines with new. I eliminated all the factory plastic lines. I used fuel line on the larger vacuum lines such as brake booster. The intake is sealed nice. Checked the pcv. Breather connections are tight. I have "reduced performance" message along with CEL. New plugs and coils, new valve cover seals. I have 4 new oxygen sensors. Fuel pressure is 38 lb at idle going up to 50lb at 2000 rpm. The car hesitates and stumbles and will not go above 3000 rpm on hard acceleration. It gets up to about 3000 rpm and then cuts out bad and bucks until I reduce the throttle pressure. Just about everything is new or in good shape. The only thing I haven't replaced is the MAF, but I don't get that kind of code. any ideas out there? thanks in advance. Sam

 

Sam, yes you are getting that code. Having both P0171 and P0174 simultaneously indicate that you could have an air leak in your intake, or your MAF is either extremely dirty or has gone bad. Having both codes means there is a problem with both banks, the problem that is common to both banks in this case is not fuel related, but instead it is intake related.

If you are sure your intake is not leaking, the PCV is not broken or leaking, and that the vacuum lines, specially the ones that connect to the throttle body are all good, then your next step is the MAF.

Make sure the harness is properly connected, that the harness contacts are clean, and that the sensor itself is clean. If the sensor is soiled, try using MAF cleaner. If that doesn't work, then it may be time for a replacement MAF.