High LTFT (stock tune)

[Bratvold]

Yesterday I got my cats replaced (P0430). Before throwing the code I would get a low voltage O2 code comming from the after cat left bank sensor (the bank that didn't throw the 430 code).

In the past I replaced the sensor, but nothing changed. I would get a 50-60 mv during idle, but good values under WOT. So when I would get the code I would delete it (about once every 3 months).

Now since getting the cats replaced the O2 reading has went back up even at idle! ( :) ). Must of had a non-code throwing restriction in it.

My question is....I take care of the engine, but my prediator unit still shows high postive LTFT values (+14+15) with the stock tune (all throttle positions except idle).

Is this going to ruin my cats again in time? What else can I look into? EGR? AIR pump? MAF? Etc. Thanks.

Car: 2000 Z28
Mods: Lid, Holley filter, LM, FTRA

[jimmyblue]

This is a stock-manifold car, yes? The output being way
low and not bouncing is a symptom of running too cool.
A stock exhaust vehicle shouldn't have this problem.
But you might verfy that you have heater power to
the O2s at startup.

A whacked MAF is the easiest way to get positive trims
on an otherwise-normal setup. But sleepy O2s also drive
positive trimming, trying to get a high output off a
sensor that just won't give it. You would have to learn
this out. It might be worthwhile resetting the PCM to
speed this process (not having to learn from + to -,
but only 0 to -).

[Bratvold]

Originally posted by jimmyblue
This is a stock-manifold car, yes? The output being way
low and not bouncing is a symptom of running too cool.
A stock exhaust vehicle shouldn't have this problem.
But you might verfy that you have heater power to
the O2s at startup.

A whacked MAF is the easiest way to get positive trims
on an otherwise-normal setup. But sleepy O2s also drive
positive trimming, trying to get a high output off a
sensor that just won't give it. You would have to learn
this out. It might be worthwhile resetting the PCM to
speed this process (not having to learn from + to -,
but only 0 to -).


My O2s are fine now so I'm happy.

I will try to take a look at the maf? What is the cleaning procedure for a MAF?

[Bratvold]

Originally posted by jimmyblue
This is a stock-manifold car, yes? The output being way
low and not bouncing is a symptom of running too cool.
A stock exhaust vehicle shouldn't have this problem.
But you might verfy that you have heater power to
the O2s at startup.

A whacked MAF is the easiest way to get positive trims
on an otherwise-normal setup. But sleepy O2s also drive
positive trimming, trying to get a high output off a
sensor that just won't give it. You would have to learn
this out. It might be worthwhile resetting the PCM to
speed this process (not having to learn from + to -,
but only 0 to -).

The MAF was the problem. I checked the MAF and they were filthy. Cleaned them and everything is pefect. Thanks.

[smiley]

excess oil from your filter?

[Bratvold]

Originally posted by smiley
excess oil from your filter?


Yep

[cainsw]

What is the MAF cleaning procedure?

[JandJsTA]

I used an aerosol contact cleaner and there was no need to touch the MAF wires at all (very delicate wires) :)

You guys may also want to look at the K & N warning at the top of this forum :) ... just in case you have to make a stealership visit ;)