Air fuel adjustment/Fuel trim ? - Page 2

gsfent · 7th May 2010, 15:13

Quote:

Originally Posted by camlob

1) Change the air filters. Cleaned them since it came with k&n filters. I didnt oil them!

Then you haven't really cleaned them properly. The oil is designed to help catch dirt particles. I suggest you oil them, and then LET THEM DRY FOR A COUPLE OF DAYS before you reinstall. Most people over oil them and the excess oil can foul the MAF's.

Regards,
Jerry

ard · 7th May 2010, 17:44

1. change the fuel filter
2. Replace the K&N filters with PAPER FILTERS
3. Run the MAF/Fuel flow test (look in the FAQ post that is stickied at the top of the page

Report back

I suspect the mechanic was seeing whacked out fuel trim numbers, and hence wanted to adjust them- he is ignorant and failed to understand that it is bad mafs (ie fouled mafs) that CAUSES fuel trims to distort...

A

AMP · 7th May 2010, 23:47

Quote:

Originally Posted by ard

1. change the fuel filter
2. Replace the K&N filters with PAPER FILTERS
3. Run the MAF/Fuel flow test (look in the FAQ post that is stickied at the top of the page

A

Yes, yes, and yes!!

IMHO K&N filters suck. Sure, they flow better, but the oil will foul up the MAFs. I see it day after day here...

It is possible to clean the MAFs to a certain extent, but it may be too late (and new ones aren't all that expensive).

camlob · 9th July 2010, 05:29

So just installed the plugs today and finally the car is perfect! Strangely, I was expecting a badly fouled plug but I didnt find any. Only one that slightly had a darker brown color than the rest. Phew, I was ready to look for vacuum leaks, changing the MAFs and CPS sensors, O2 sensors etc.

TMcNasty · 9th July 2010, 06:02

glad to hear camlob! The DME does take a lot into consideration. Replacing any of the parts above is a great idea depending on mileage. I strongly suggest replacing the oiled air filters with plain paper ones along with new GENUINE Bosch MAFs. The oil is notorious for coating the MAF sensors and making them less efficient. Yours are most likely contaminated and causing power/mpg loss as well. The contamination can only be partially removed with cleaning solution. Consider some of it baked on permanently.

Notice also from the .pdf you linked that pre AND post cat O2's affect the fuel mappings as well. I consider it a detriment that your car is missing its cats. How many O2 sensors are installed? 0, 2, or all 4? Also how many miles/kilometers are on this car?

camlob · 9th July 2010, 06:41

Tim - 4 O2 sensors are installed. The car has 23k miles on it. Yeah I think MAFs will have to be changed. Can you suggest any vendor that sells them at a reasonable price? I read that bimmerzone sells them cheap.

ard · 9th July 2010, 08:18

Quote:

Originally Posted by camlob

finally the car is perfect!

So you fuel flow tests (ie MAF tests) are running 140 L/hr at WOT when you hit redline in 3rd gear????

camlob · 9th July 2010, 08:26

Ahem...well maybe perfect in the sense it doesnt sputter at low revs. Ill do the test but I am more or less decided to get new MAFs as a preventive measure.

TMcNasty · 9th July 2010, 20:21

Bimmerzone best bet I think. Replaced mine at 91k. Definately regained lost mojo doing them.

camlob · 10th July 2010, 09:41

So my nirvana was shortlived. Just today I experienced the richness again, sigh. So I will be ordering the MAFs and O2 sensors. I dont see the logic on why cam position sensors will affect fuel trim? Should I order them anyway?