For the last few years when it gets cold/wet out I would notice a P1128 (long term fuel trim too lean) CEL intermittently. Intermittent, as in, clear it and it won't come back for weeks/months. Not so easy to troubleshoot. Now it is winter again and this year it is coming on every 2-3 drive cycles. I wouldn't care because the car runs great, but my emissions inspection is due this month and I don't fancy driving around with an expired sticker.

Fun part: The light ALWAYS comes on when the car is decelerating or coasting, typically when traveling at highway speed, almost always when decelerating for an exit ramp. There are no other stored codes.

Because I had a parts car, I went ahead and shotgunned the following parts (no reason to assume they were good, but the prior owner said the only problem w/ the car was a busted timing belt):
MAFS
IAC
EVAP solenoid up front (verified operation of both solenoids on bench, need to check they are getting signal in the car)

I need to get a fresh gas cylinder for my torch, but there are no obvious gross vacuum leaks.
Exhaust manifold & cat. assembly is new, and the codes did not come more frequently before/after the replacement.

I need to have a peek and see if I need to clean the throttle body but it would surprise me if that were the problem
I'll see about swapping in my spare front O2 sensor
Fun next part: trying to see if fuel injectors are spraying right (any hints on cleaning them?) then the FPR and fuel pump

Comments? Does anyone want to fix my car for me, free? 02.gif

Matrix:

 

check the o2 sensor and it's connections

i stumbled in a similar problem with my santa fe

 

That's for lunchtime today. If I remember. Then I'll be back in a couple of days to say if it helped or not.

 

Here's the old sensor. When I pulled it out, my comment was "Man, that's running lean as (deleted)!" which of course is what the ECM thinks also. Cross your fingers and we'll see if this is the problem. Good news: the car started and didn't idle like poopy when I had installed the new (to this car) sensor. I reset the CEL and we'll see what happens.

 

now my swapped beater just started to act today..
p1128,eratic idle...

might be the o2 or maf or it didn't like the freezing temperature we have for the past days (-15°F)
i'll log the fuel trim and O2 activity for now

i'll see what will happen when the wheather gets a tad hotter

 

A busted turn signal prevents me getting my car inspected but the CEL stayed away for good. Call this P1128 O2 sensor-related.