Hello, I have a BMW 325i E46. OBD II reading of P1156, P0172 and P0175. on 2001 BMW 325i

I've been working this issue for some time now. I have cleaned the throttle body, idle control, replace all O2 sensors, The MAF, The MAP, cleaned the Fuel Injectors, replace the Temp sensor, replaced all air filters, all the airlines, the fuel filter and the pressure control valve. I cannot think what else I can do? I sent it to a Bosch shop and they couldn't figure it out. My Gas mileage is about 16.3mpg and it idles badly from the start but smooth’s out after about a minute. I really don't want to send it to the shop and was wondering if there are a couple of DIY things I can do before wasting my money at a Dealership. Thanks

by in Pittsburgh, PA on October 14, 2012
3 answers 4 comments
ANSWER by on October 14, 2012
did you have the coolant sensor checked at the bosch shop?? Roy
COMMENT by on October 14, 2012
Sorry forgot to add that. I replaced that too. :( Also I just completed cleaning the Fuel injectors. The light came back on and as I started the engine the Idle was bad and the exust smell bad. I took for a spin and I returned the exust was fine, stunk a little but far better and the idle was back to normal. I checked the generic OBD II codes again and I received codes of P1156, P1100 and P0004. Every time i change somthing on the car the codes will default back to these three codes over time they change, P1156 always stays though.
ANSWER by on November 03, 2012
Rough idle and poor gas mileage could be a sign of worn VANOS seals. Many M52 engines need to do a VANOS reseal after about 120k, sometimes sooner.
COMMENT by on November 03, 2012
Sorry, VANOS seal is the Valve Cover Gasket? Funny because i just change my spark plugs and the threads on my old Spark plugs had oil on them but where the spark hits is clean. Would that be the Porblem?
COMMENT by on November 03, 2012
The VANOS is the mechanism that controls the valve timing on the intake and exhaust camshafts on your 325i. It is linked to the timing chain and is controlled with oil pressure. There are seals that wear in this mechanism. Our shop does a repair that includes the seals, spark plugs, and valve cover gasket for about $600.
COMMENT by on November 04, 2012
This is definatly the problem. I'm a Soldier stationed in Germany and every machanic here just tell me to change the O2 sensor on bank two. I knew that wasn't correct. Even the BMW dealers here. I got to tell ya thanks for all the help. I'm not a machanic in any way but like to work on my own car. Thanks again!
ANSWER by on September 11, 2013
Try the oil separator under the intake manifold.

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