My truck is:
99 5.3L with k&N intake, pacesetter long tubes with catless y-pipe into flowpro single in duel out mufler then duel pipes. Stock tune, 105,000 miles.
I put a wideband inovate setup on it last nite and the bitch is running 15-16 to 1 air fuel at idle and very slow cruizing. It is throwing a running lean code.
When I punch it all the way up to 5500rpm its running around 11 to 1 (rich in my mind).
I dont care that its lean at idle because it wont hurt anything but why is it doing it?
The comptuter is in closed/open loop(I always forget which is which) at idle and slow rpms, so does that mean it is or isnt using 02 sensors? They are the origionals with 105k miles on them, so they probably are worn out. Also, would it be the mass airflow sensor that would be throwing it off, maybe just needs a good cleaning? I dont think its injectors because they work fine under WOT. Spark plugs are relatively new(less then 10k)

 

anyone?

 

Is your MAF de-screened?

 

nope stock maf, but might be dirty?

 

I would think an intake leak or a maf issue are the two things to suspect.

 

I hosed the maf off with some electronic contact cleaner and it is still running pretty rough at cold idle. I also cleaned the idle bypass plunger.

Would it be that the 02's arent close enough to the engine with the long tubes or that they arent heating up fast enough. They do have 105,000 on them. I am just trying to figure other things out before I drop $120 in new o2's