Changing tune??

[1977and2010]

I have a question for any of the tuning gurus. I have a 2010 2SS LS3. I've put on a Vararam tune intake, ported intake/throttle body, ARH 1 7/8 LTs with HF cats, and Magnaflow axlebacks. I've had these things on for quite a while with no problems. About 5-6 months a go I put in a Vengeance Racing stage 3 cam with all of the supporting parts by myself, install went well. I gingerly drove it to my tuner and had it tuned. For several weeks it drove great, 60 more rwhp and sounded awesome with some slight surging/bucking in 4th gear at 30-40 mph. I expected this and it was nothing I couldn't live with. Then maybe 3 or 4 weeks later it started with quite a bit worse surging/ bucking and the idle would go up to 1200 rpm when I would shift to neutral while coasting to a stoplight. When the car would completely stop, the idle would settle to the normal 775 rpms. I went back to my tuner and he adjusted things again and it ran even better after this tune. Now a month or two after that tune its surging/bucking worse again and now when I put it in neutral when coasting to a stop the idle goes up and down from 775 to 1200rpms.

My tuner is pretty well known. He travels around the east coast tuning all kinds of GM cars so I trust him. He really seems to know what he doing. But could there be something he's missing? Has anyone else had this happen? Is it the computer trying to change things on its own?

Thanks for any words of wisdom.

[Crime2]

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Sent from my iPhone using Tapatalk. If is spelllled wrong deal with it.

[izaks]

Post your tune and a log.

[1977and2010]

Originally Posted by izaks

Post your tune and a log.

I would if I could but I have no way of doing that, sorry.

[Rhino79]

How much does the car get driven? I only ask because there are learned idle and fuel trims that could be adjusting themselves back to a place that is causing the funky run-ability.

[1977and2010]

It's not my daily driver but still fairly often. Right now I'm breaking in a new clutch so I'm driving almost everyday.

[Slowhawk]

I think he meant- did the tuner go out and drive the car around then adjust the tune?

[1977and2010]

Oh sorry. First time was tuned on street then dyno. Second time was on street. Both times on street was with me driving him in passenger seat. And we drove around for half hour at least.

[Blue Thunder2]

The question is whether or not the afr is set properly. It takes a bit more than 30 minutes to get it right. Probably, what is happenting, is that it is depending on the O2 sensors to bring the afr into play. When calibrated properly, you could have an O2 completely fail and the only way you would know is that you would get a check engine light. Also, if he didn't turn off the ve tables and calibrate the maf, it would automatically switch back to the ve tables at those lower rpms anyway....which again, the computer would make adjustments by itself....affecting your tune. All this , of course, is speculation since we are not able to view your tune and make suggestions.

[Blue Thunder2]

Originally Posted by 1977and2010

Oh sorry. First time was tuned on street then dyno. Second time was on street. Both times on street was with me driving him in passenger seat. And we drove around for half hour at least.

That won't matter. Doesn't have to be tuned on the dyno to afr and timing set right. It's all in what he's scanning.

[Rhino79]

It uses a blend of ve coefficients and maf all the time anyways except for wot. In closed loop, the fuel should be kept in the target zone anyways. There are airflow proportional and integral tables that effect rpm correction in normal mode and coastdown as well. I would make sure the fuel trims are in check, timing is good (not excessing overspeed or underspeed correction), and minimum required or base airflow before messing with the other modifier tables.

[Rhino79]

You cant really adjust afr's at part throttle without maf tuning. He can use the stock o2 mvs to base the changes from, but the maf will still need tuned. Fuel trims within +/- 5% is pretty good because they will always change, day to day depending on conditions.

[1977and2010]

I'm taking all of these suggestions to give him when I call him up next week. Thanks again fellas. I guess thats how he does the tunes WOT afr with the wideband on the dyno and then everything else on the street.

[Steck]

Sounds like purely a final idle airflow issue coupled with timing problems. I doubt your MAF/VE calibration (or lack thereof) is the problem.

Why not take it to Tampa Tuning? He's local and isn't completely stupid (only slightly!).