LTFTs killing me HELP please

[white1]

I got a '99 Silverado with a 4.8. Swapped in a PCM from a '02 1500HD re-flashed with a stock tune and my VIN.

Till I got the time all I messed with was the timing, and transmission stuff

On all my logs, I noticed my LTFTs extremely high (25+)

I decided to get this thing straight, so I set my MAF fail frequency to 0, and moved my PE up to 99%, reset my fuel trims, and started to log.

Ive been logging, copying my LTFT histogram, and adding it to my VE, then repeat. Reset fuel trims, and log. Ive done this 3 or 4 times, and still my fuel trims are in the 17-20 range. This is after adding 20-25 to the VE 3 times.

I was thinking my tune may have been from a later year with larger injectors just with my VIN, but from what I got out of the HPtuners tune repository, everything looks correct.

What gives? My (new) O2's are reading a little low, but not enough to really concern me (840-870) but Im concerned about the LTFTs. My injector duty cycles are normal (stays under 75% or so WOT)

Someone mentioned that I should disconnect my MAF, so I may try that on the way home in the am, but the LTFTs were this high before even starting to tune.

I do have a set of injectors off a newer (03 I think) 5.3 I can swap in, but I really dont think thats necessary at this point.

Im totaly lost right now and appreciate any help.

Thanks

[RedHeartbeat]

Do not descreen the MAF, its not worth the headaches.

[foggy]

Are you saying that your O2's are only cycling between 840-870?

[blown 04]

did you set your maf dtc po103? I might be wrong but i think you have to do this for the maf to fail.

[farmtruc]

Here's some info:

You zero'd the maf, so that eliminates a vacuum leak, it also eliminates a suspected bad maf. No need to worry about the maf codes if the maf hz is zero'd out.

you're doing right by working the ve table, however you're noticing ltrims are still high.

be sure the o2's are toggling up and down from 50mv to 900mv.
If not, set the Engine > Fuel Control > OL % CL > Closed Loop Enable table to MAX.

This will keep the pcm in open loop. Drive around and notice if the a/f ratio gets richer by increasing the ve table. If it does, it's probably the o2's because the o2's play a huge part in adding and trimming fuel.
Since the o2's are no longer playing a big part in open loop, they will not send a false signal to the pcm, making the pcm think that the a/f ratio is lean, hence high ltrims.
Be sure to reset your ltrims and see what they do.
Oh ya, taking note of the wideband, if you have one.

It could also be low fuel pressure, but i doubt it since idc is ok.

This is just what i'd do, take it for what it's worth, hahah.

[white1]

Here's some info:

You zero'd the maf, so that eliminates a vacuum leak, it also eliminates a suspected bad maf. No need to worry about the maf codes if the maf hz is zero'd out.

you're doing right by working the ve table, however you're noticing ltrims are still high.

be sure the o2's are toggling up and down from 50mv to 900mv.
If not, set the Engine > Fuel Control > OL % CL > Closed Loop Enable table to MAX.

This will keep the pcm in open loop. Drive around and notice if the a/f ratio gets richer by increasing the ve table. If it does, it's probably the o2's because the o2's play a huge part in adding and trimming fuel.
Since the o2's are no longer playing a big part in open loop, they will not send a false signal to the pcm, making the pcm think that the a/f ratio is lean, hence high ltrims.
Be sure to reset your ltrims and see what they do.
Oh ya, taking note of the wideband, if you have one.

It could also be low fuel pressure, but i doubt it since idc is ok.

This is just what i'd do, take it for what it's worth, hahah.

Thanks Allan (or is it Allen??)

I dont have a wideband as of now. I never paid attention to the minimum of what the O2s are cycling to, but will try what you said. I just replaced the O2's but it was doing the same thing with the old ones. I know brand new stuff can be bad, but I replaced both O2s, and they are tracking with each other so Im guessing its not them.

Hopefully I can get all this dialed in soon, as Im getting the itch or a cam. Especially since Ive decided to go a slightly different route with the 6l, so Im gonna run the 4.8 a little longer than expected

[ss6speed]

get a wideband, it will make tunning 10 times easier and take the guess work out of things.

[Atomic]

setting pe to 99% is a bad idea. do you really want to be at 99% throttle with no extra fuel?

you dont "add" the trims, they are a percentage, so you multiply by %. right click > paste special > multiply by %

get a wideband

[white1]

setting pe to 99% is a bad idea. do you really want to be at 99% throttle with no extra fuel?

you dont "add" the trims, they are a percentage, so you multiply by %. right click > paste special > multiply by %

get a wideband

I just wanted to make sure I didnt go into PE mode is why I set it at 99%.

Ive read to multiply bu % also, but wouldnt that be adding less than if I added to the VE? Either way, my main area I run in the VE tables are in the 117 area and my LTFTs are still in the 11-17 area. Stock VEs about 45-55 and my LTFTs are 27. Im lost!

[farmtruc]

You can multiply or add to increase the ve table to see results. The point is , when ltrims are positive, you add, anyway you want., manually, % or add, etc.
You're just not seeing any improvement.

I bet it's the o2 sensor, they can cause headaches.