idling problems. P0171 and P0174

[osmononame]

Hi all,

 

I have been having issues with my Zed for a few months now and seem to be no closer to finding a fix. I was getting P0171 fault code - bank 1 running lean. Mechanic thought O2 sensor so it was replaced. Didn't fix the issue. They had the car for ages, we replaced o2 sensors on bank 1 (upstream and downstream) but couldn't find the cause for the rough idling (although didn't charge me as they couldn't find the fault). I have been living with it since I picked the car up and today I thought I would scan the codes to see if it was still they were the same but today the code was P0174 (up until today the code had always been P0171 indicating only bank 1) which is bank 2 running lean. A quick Google search shows it could be any of three issues:

 

1) MAF

2) Fuel filter / Fuel pump

3) Vacuum leak

4) ???

 

A bit of reading informs me that this is unlikely to be an o2 sensor issue due it affecting both banks. My mechanic tells me that the readings for MAF are fine and it’s definitely not the problem. I believe these cars have integrated fuel filters so I would have to replace fuel pump to eliminate this. This leads me to vacuum leak - I have checked online and the most comprehensive way to check is to do a smoke test but can't find anyone locally that is able to do this (my mechanic cays he has checked for this too but I don't know what method he used).

 

I am at a loss and it's really frustrating. This is the best driving weather we have had in ages and I can't even enjoy my car. It sounds like a tractor / diesel when idling. It's horrible.

 

Does anyone have any suggestions or could recommend someone in central Scotland who could have a look at it? I am wary of main dealers as I was ripped off replacing this and that when the car kept stalling. I took it to my guy who diagnosed it as a faulty crankshaft sensor at his first attempt.