Possible missfire, can I log for it?

[JohnForeman]

I set my LTFT's this weekend and everything seems to be ok - sorta. I adjusted my LTFT by -6 which from what I understand told the computer my injectors were small so it's dumping more fuel. That would explain why my mpg dropped from low 19mpg to mid 16mpg. Does this sound correct? Also, I took it out for a hiway cruise this morning and thought I was feeling an occasional missfire. I didn't hear any popping that would indicate any backfire or exhaust popping, just felt like it was stumbling at cruise. I had the cruise set to 68mph. I didn't feel it at any other time. I have the 93 octane tune with DOD off and LTFT's set at -6. Speed limiter is also off. Engine is bone stock. So, can I use the predator to log and see if i'm getting the missfire or if it just me being paranoid? What parameters should I log and what do I look for in the log?
Love this web site by the way - by the time it's all said and done, you guy's are gonna make a tuner out of me yet!
-John

[06MonteSS]

yep, you should be able to log misfires...

go into the gm complete/full list of parameters (not the short list), and the misfire parameters are in there that you can select to log...

[Poetique]

I set my LTFT's this weekend and everything seems to be ok - sorta. I adjusted my LTFT by -6 which from what I understand told the computer my injectors were small so it's dumping more fuel. That would explain why my mpg dropped from low 19mpg to mid 16mpg. Does this sound correct? Also, I took it out for a hiway cruise this morning and thought I was feeling an occasional missfire. I didn't hear any popping that would indicate any backfire or exhaust popping, just felt like it was stumbling at cruise. I had the cruise set to 68mph. I didn't feel it at any other time. I have the 93 octane tune with DOD off and LTFT's set at -6. Speed limiter is also off. Engine is bone stock. So, can I use the predator to log and see if i'm getting the missfire or if it just me being paranoid? What parameters should I log and what do I look for in the log?
Love this web site by the way - by the time it's all said and done, you guy's are gonna make a tuner out of me yet!
-John

You LOST 3 MPG? No... no that shouldn't have happened. Even though you're technically telling it to spray more fuel, the point of that is still to achieve better overall performance and equal or better gas mileage. With that said, give it some time and see if you at least get back to where you were, and don't forget temperature effects such. Also... make sure you didn't catch lead foot syndrome after tuning like many of us do lol.

[jonathanalberto007]

From my experice doing this, i have noticed that it for my 2004 Chevy Avalanche it doesn't take 50 to100miles, it takes about 2to 3 gas tanks to be able to see good results. At first the readings stay the same with some drop in performance but untill it settles it shows very good gains Just to give you an example on the last log it DSlogredux advise mea -3 increase on my injector slope to a -11 didn't saw any positive gains it might have lost a mpg or so, but then after running about 3 tanks and from averaging 16 to 17 miles per gallon, I saw an improvement of 21 to 22 miles per gallon. Then did a nother log and it said no change so I left it as that, of course the temperature has droped from 100 to the 80s.SO I will wait to summer time again to do another log, mean time i am happy with results.

My suggestion give it some time for computer to learn new parameters. AS not all vehicles are the same.On my case may be something is wrong with my truck, but who knows as it is working just perfect and fast.

[06MonteSS]

nah, nothing is wrong with your truck... i've seen it happen before, especially with vettes... they like to go 150-200 miles before things are relearned and settle in...

but most vehicles are usually good by about 75 miles or so...

[jonathanalberto007]

MonteSS,

I thought so, becasue I was eventually giving it 100 miles, untill one day I travelled a long way and 3 gas tanks later I have seen very huge results from the last install, that I decided towait and on my next trip it happened again. Now I have to wait till temps get any where to 120 like before so I can re log and see if the last log was successful and dont have to log for a while. I really love seeing mpgs from 18 to 22 like before it was 14 or 16 so that is some great results so far. But on mine it can take from 250 to 350 miles before the changes get set in.