Newbie could use help with a 2003 GMC Sierra

[camaroguy28]

The auto saving that he is referring to is that scan file will automatically save you scan when you are done. you will have to search through your files to find it, but it should be in there somewhere if you ever forget to save the scan manually.

I looked at the second log, and I agree that the long term fuel trims or ltft are pretty lean. a positive number is lean, and a negative number is rich. are you absolutely sure that nothing on the truck like the intake or anything that may help the air flow better has been changed? The firebird I have was running more lean than the truck, but I have a port matched upper and lower intake manifold, a v8 style intake and a few other small things to help get more air in it. if nothing else has been changed, then it seems as though like 5FDP has stated, you either have a leak before the o2 sensors or you have a vacuum leak. Since the ltft are the same on both sides, it leads me to believe that it isn't an exhaust leak because I would think that would only register on the bank that the leak is on. I may not be correct on that, but 5FDP knows his stuff, so he will chime in and clarify if I am wrong.

My next question, is do you have a wideband o2 sensor? That really helps dial everything in closer, and in my opinion much quicker than with fuel trims. if so then try to hook it up and get a few logs with it. If not, and you don't plan to tune any other vehicles, then I don't know if I would get one since you aren't trying to make it a hot rod. it would be good to know what the actual afr is when you go wide open throttle though.

check for vacuum and exhaust leaks and see if you find anything out of the ordinary there, and let us know.

[james38340]

Thanks for the info. Iam sure that it is all stock and nothing has been done so it must be a leak. I plan on changing out the thermostat and looking for a leak on it this weekend. As for the wideband o2 sensor I may get one but I currently don not have one. Thank you for the good advice and I will post what I find.

[camaroguy28]

Ok, keep us updated on what you find. I guess there is a possibility that it is just a lean tune on the thing, but I would be surprised if it was.

[james38340]

Ok, keep us updated on what you find. I guess there is a possibility that it is just a lean tune on the thing, but I would be surprised if it was.

Okay I checked it for leaks and I did not find any using Carb cleaner and listening and visual. I got my 10mm socket and verified the intake bolt and front two seemed loose so I tightened them up some. The thermostat started working so I took it to the parts store to buy a new one and scanned it on the way. This is what I got. I really think it may be in the tune cause it runs great but shows way lean. Any suggestions? Thanks James

[camaroguy28]

If everything seems to be sealed up tight and is not leaking, you could start tuning the ve table using the short term fuel trims+long term fuel trims. That would bring it down where it needs to be. There are many guides about how to do this, so you could try that. After you get the ve table close, you could do the mad table. You cannot tune wide open throttle correctly without a wideband though. Just do idle and partial throttle tuning. I would do this only after you verify that it?s not an exhaust or vacuum leak.

[cobaltssoverbooster]

i would do what camaroguy28 said to do but if you can research how to use the histogram filters and include a filter on the stft+ltft histogram that removes any PE zone. its pretty easy to setup; should look something like [commanded afr pid #]>14.4
it will go a long ways in removing garbage information that could ruin your ve table.

[james38340]

i would do what camaroguy28 said to do but if you can research how to use the histogram filters and include a filter on the stft+ltft histogram that removes any PE zone. its pretty easy to setup; should look something like [commanded afr pid #]>14.4
it will go a long ways in removing garbage information that could ruin your ve table.

Could both of you guys please take a look at the scan now and tell me if I'm getting it better. I adjusted many tables and compared to another 4.3 and It seems to be better I think. Your guys thoughts would be great. Thanks James

[camaroguy28]

what tables did you change, and how much did you change them? it is still pretty lean in most every place, but if I remember correctly it was maxed out before and now seems to be a bit better than before. are you using a certain guide to help you tune or are you trying to just wing it and see where it gets you? Not trying to pick or criticize just trying to see where youre coming from to know how to better help you dial it in.

[james38340]

what tables did you change, and how much did you change them? it is still pretty lean in most every place, but if I remember correctly it was maxed out before and now seems to be a bit better than before. are you using a certain guide to help you tune or are you trying to just wing it and see where it gets you? Not trying to pick or criticize just trying to see where youre coming from to know how to better help you dial it in.

I changed several and so many that I really can't recall them. I was using a friends that has been tuned and copy and paste the ones that were somewhat close but different if that makes sense. It seems to run better but I think it may be little to hot on timing now. I thought I would just try it and I could always put my original tune back on it. I have noticed it seemed to cause my fuel gauge to stop working like it should...seems to stick and then start working. Not sure why that happened.

[camaroguy28]

I would change it back to stock, and then just work on tuning the ve and mad tables. I used Russ k?s guide in the v6 engine sticky section, and it was a very complete guide and easy to follow. I would try that first and see if it got you closer to the ball park on your ltft?s.

[cobaltssoverbooster]

rule #1 always post an initial tune file and log to start a thread. (You've done this one for the most part)
rule #2 start from stock and go from there. (You deviated so this could make things hard to track)
rule #3 if you post a log you post the tune file to go with that log. We cant track the quality of changes made without the log and editor file for the changes that have been made. (You're missing half of this one)

as camaroguy28 stated the stock file is the best to start from. you should then just focus on tuning the fueling only which he also recommended. dont worry about anything else but the fueling as this tends to clean things up quite a bit all on its own.

[james38340]

I would change it back to stock, and then just work on tuning the ve and mad tables. I used Russ k?s guide in the v6 engine sticky section, and it was a very complete guide and easy to follow. I would try that first and see if it got you closer to the ball park on your ltft?s.

Okay that is good idea and I have already went back to the tune that was on it. The modified one that I copied from a friend was not working for me so I went back after that one scan. Thanks for the tip and I will try that.

[camaroguy28]

have you gotten a chance to tune on the truck lately?