My car had been running lean in bank 1 almost since the time I purchased it a few years ago. I had put AFE high flow filters in a couple of months ago and did the charcoal delete. It didn't make any difference to the lean condition in bank 1 (LTFT was about -10% while bank 2 was just about perfect).

Lean condition recently became worse and triggered a CEL condition caused by bank 1. I cleaned the Mass air flow sensors as I'd seen recommended here on the site which cleared the CEL. Bank 1 continued to run lean though (LTFT -8.6% in Bank 1, while Bank 2 was near perfect). In reading all the threads on the topic it appeared cleaning the sensor was a temp fix so was hunting down a replacement sensor when I happened upon a good deal for a ROW air box set that included sensors.

I installed them tonight and was very pleasantly surprised by how much they changed throttle response, overall smoothness of the engine and a slightly throatier exhaust note. Performance was also good, I broke the tires while accelerating from 80km/h (50mph).

So far this all sounds good but... in monitoring LTFT it now seems the engine is running rich, which I find a bit confusing. It is not setting off the CEL, however I am about 3% rich on Bank 1 and almost 10% rich on Bank 2. I thought if anything the the opposite would have happened, with the air coming through the AFE filters and the more open air box, the engine might run lean.

Thoughts on why this might be happening? My own thoughts to start:

1) Will take some time for the computers to adjust to ROW boxes? (I only drove about 5 miles in total after making the change)
2) Will I need to find a better set of high flow filters? (I have AFE high flow filters now so not sure if there is anything better?)
3) Will it just signal this way because the car is programmed as North American with charcoal filter (which means I do nothing and just enjoy the ride?)

Thanks in advance for any insights any of you might have.

James

 

First of all I have the exact same experience regarding the difference in throttle response and exhaust after changing to the boxes as well with the same filters. And no those filters I think are the best for the car in terms of flow durability and keeping oil off the mafs

I think the mafs that come with the boxes are somehow read differently by our software here in the states so I wouldn't really trouble yourself over it. 5 miles is certainly not enough however I would think more like 50 or 100 miles should be enough to reprogram with hard driving in sport.

 

Ive had my free flow boxes and filters in for almost 2 yrs. No problems but I have not read the computer. I have had it in to MB and they made no comments about abnormalities.
(I would give it 50 - 100 mi to adjust)

 

I didn't think it would be an issue but nice to hear from others who have done this. I've also read a lot of the threads on improving air flow so thinking more air flow through is better and not worse. I do find it confusing the car is running rich, which explicitly means it is not getting enough air into the engine. Seemed counter-intuitive when everything I've done should be letting an excess amount of air through. I'm thinking there is a link between the new sensors and old computer settings so hope will normalize over time.

Also on the bright side along with slightly better performance it also seems to be better on fuel, although in this car that is a relative measure, lol

Thanks again.

James