I am kind of pulling my hair out, trying to figure out why I have fuel trims around 24% or 25% at idle. I recently installed a rather inexpensive(cheap) mass air flow sensor for $45, because of a huge bog on hard acceleration from a dead stop. The next cheapest sensor was $134.

Before I installed the mass air flow sensor I was getting 1638, 1642, and 1797 codes for the can link circuit. Those faults have not reappeared. Now the car runs great out of the hole, but I am getting bank 1 lean, and bank 2 lean faults, which are putting on my check engine light. It is also giving me a restricted performance message every now and then.

I replaced the intake manifold gaskets yesterday, since I had to replace the thermostat tower anyway, but there has been no improvement. I have sprayed about every vacuum hose and joint I can think of. Do you think it could be the new mass air flow sensor, maybe being out of specs for this car?

I know I might have screwed up going cheap, but on a fixed income that comes with the territory. Any ideas would be welcome at this point, including maybe buying a quality rebuilt sensor.........Thanks in advance......Mike

 

Did you have DTCs P0171 and P0174 prior to replacing the MAF?

 

If it will make you feel better I got my MAFS from AutoZone and it worked just fine. However, my first one was a reconditioned one and it failed my test. I have a test chart on my page that you can perform to see if it falls in line.

Gus
www.jagrepair.com

 

No I did not, but who knows if those 2 codes could have been hiding in the can network codes.....

 

Isn't P1646 an O2 code?

If your battery is even vaguely suspect quit worrying about codes and replace it, otherwise looks like you need an O2 and so trims may be weird.

 

I recently replaced the MINA cold air system, and went back to stock. It has taken care of my fuel trim problems at idle. My long terms are around 4, and short terms sit right around zero. It appears that in order to get a little more fuel flowing, the Mina system actually is a little smaller in diameter, causing the MAF to sit in a higher velocity of air, causing me fuel trims of 19.5 long term, and 17.5 short term

Anyway, I am now getting lean bank one, and lean bank two codes, after a couple hours of highway driving, and it is driving me crazy trying to find the cause. I installed a new fuel filter. My fuel pressure is 36 at idle, and 46 at wide open throttle, sitting in the shop. I do not know what the fuel pressure is, going down the highway, because of the way our hoods latch.

For the emission test, everything is in the ready mode, except for the oxygen sensors, and they are functioning well enough for the fuel trims at least, according to the scanner.....Once again, any help would be appreciated.......Mike

 

Have you checked for vacuum leaks as they will cause P0171 and P0174.

Sometimes a small leak is difficult to find if a part is cracked and only leaks when hot. If you cannot locate the leak, a smoke test may be in order.

 

After a heat soak the fuel trims are still fine. Wouldn't a small vacuum leak kick them up higher, than what I have? We inspected the intake manifold, when we replaced the intake gaskets, and it looked good. We have been using a MAC TOOLS smoke machine, and it isn't showing anything yet. What are common places for leaks? We have tried the throttle body, the tubing after the MAF, the intake manifold. Could it be fuel pressure dropping off under load?......Thanks......Mike

 

Brake booster circuit?

 

Hi Gus,

would you mind to post a link to your MAF test proceedure. I visited your site and was unable to find it.

Thanks !

 

Use this link and scroll down to MAFS Readings.

Link. http://www.jagrepair.com/jaguarxk8xkr1997_2006.htm

Gus
www.jagrepair.com

 

Thanks for the link