Help diagnosing engine issue

[DC_M35_07]

2007 M35x AWD with 98K miles, service engine light on continuously, rough idle with EVERY cold start with rpms going up and down between approx. 800-1200 (sometimes so rough I think it is about to cut off but never has). Issue started in warmer weather (Aug-Sept last year) and has continued through the winter. Once engine is warm with driving and turn off, no issues when restarted, no hesitation at all. Had K&N filter installed last summer and thought it might be the problem, replaced with standard filter, no change in issues. Went to Nissan Dealer with these computer (2 pgs) results (hope someone can translate):
Engine: MAS A/F SE-B1 (1.07V); A/F ALPHA-B1 (125%); A/F ALPHA-B2 (119%); A/F SEN1 (B1) (1.525V); A/F SEN1 (B2) (1.490V).
A second page had:
Engine...Part# 23710-EJ36C...DTC= P0131...A/F SENSOR1 (B1)...TIME=5
Engine...Part# 23710-EJ36C...DTC= P0151...A/F SENSOR1 (B2)...TIME=10
Air Pressure Monitor...Part # 40720-EJ20A...DTC = C1750...[Tuner data err] FL see service manual; DTC = C1751 ...[Tuner data err] FR see service manual; DTC = C1752...[Tuner data err] RR see service manual; DTC = C1752...[Tuner data err] RL see service manual...TIME = 50 for all four.

Sorry for all the wording but wanted to provide exactly what I have been given. Clearly it looks like there is some kind Air Flow issue but the techs at the dealer could not provide a clear resolution (it was their idea to change the air filter, nothing else!). Is there possibly a spark plug/wire issue (originals in the car). I bought rims and new TPMS from Tire Rack and had them reset to the car before this issue came up, which I think the Air Pressure Monitor data refers to and would not effect the engine. Tire pressure monitoring works fine in the car.

Anyone else ever had this issue? Any mechanics/techs on the board can explain the computer print out and/or give me a resolution idea?? APPRECIATE ANY ASSISTANCE! Thanks.

[Ilya]

If you had a K&N and just changed it, your MAF sensor may still be dirty. Might need to be cleaned. That's the first thing I would try, knowing that.

[DC_M35_07]

Thanks for the reply IlyaKol, is cleaning the MAF sensor a do it yourself; any good mechanic or a dealer required job? To be sure it is done right.

[Trendwho205]

Yes this definitely sounds like a mass air flow sensor problem I remember having a Infiniti i30 and I also had a K&N filter install. But the grease from the filter got on the mass air flow sensor which caused it to read incorrectly how are also like to ask that I cleaned it and that was only temporary I eventually in the end replacing it with a new filter

[Ilya]

You can clean the MAF with some CRC MAF Cleaner (specially designed for this). However, be VERY careful. I had a similar issue with K&N and my 1999 Nissan Maxima, that's why I will NEVER use a K&N filter again for my car. I ended up having to buy a $100 MAF to replace my broken one. I only use their filters on my bike(s)...because there isn't the possibility of something like that happening.

It should be a DIY, but you may want to have your mechanic do it if you don't feel comfortable. But to me the issue definitely screams MAF.

You can buy MAF cleaner at your local auto parts store...

[DC_M35_07]

Thanks everyone. I wish I knew about the possible effects of the K&N filter on the MAF, would have just left the air filter alone (continue with regular ones). Will follow up to let the board know of my results when the weather breaks and gets a little warmer (will look at DIY).

[CPJ LB]

based on the dealer readout, it also looks like there may be issues with the O2 sensors...? it may be beneficial to invest in a OBD II scanner/reader (can get at Autozone or any parts store) - I picked up an Actron pocket scan tool for under $40. It allows you to get the DTC codes and reset.

the other thing, you may need to buy a new gas cap - these tend to go bad over time.

and cleaning the MAF is very easy...DYI.

[DC_M35_07]

Thanks CPJ LB for the info!