LTFT issue at idle

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June 18th, 2011
bvd80

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LTFT issue at idle

I've been trying to tune my truck lately without any success. I've got a '02 ZR2 Sonoma with a Vortec 5.7L. These are the main mods I'm currently running.

Vortec 5.7L engine with 24x conversion
Ramjet 350/Marine cam 196/206 .431/.451
1.6 rockers, Comp cams beehive springs 26915
Shorty headers
LS2 coil packs
Electronic throttle, '02 truck TB, TAC, APP pedal
Cold air intake
Running the Cadillac Escalade or Chevy Avalanche tunes

I might add that the the engine ran great before adding the 24x conversion.

I recently did the CalcVET and am still having issue. My biggest concerns are the LTFTs at idle. Its running rough at idle only and the fuel trim on Bank 1 goes to over 20+% and Bank 2 is usually negative. When I give it some gas or am cruising, the LTFTs are not bad at all. It has great power and is smooth as long as I am not at idle. Here's a log of my idle and at cruise speeds. Tune is also attached. If anything doesn't look right, I'd appreciate the insight.

Or if there's anyone in the NE Ohio area that can get this this fixed for me, I'd be willing to compensate also....

Attachment 11178
Attachment 11179
Attachment 11180
June 18th, 2011
slows10

Tps is between 3.0-4.0% at an idle speed of 600 rpm. Iat temps 150+ degrees Are you idling with the hood closed after the engine has been running awhile ? B3807 is set for 1.56% B4108 is disabled. It seems like an AWFULL Lot of changes have been made in this tune. Not sure why as it looks like a mild engine. Curious why you went with a DBW setup? Im not sure why this tune warrants so many changes from stock? Maybe it is better to start with a stock tune again, and go from there. Im sure the pro's will chime in soon for you.
June 18th, 2011
slows10

Are they stock injectors?
June 18th, 2011
bvd80

Quote:

Originally Posted by slows10

Tps is between 3.0-4.0% at an idle speed of 600 rpm.
Doesn't this have to be that way since there is no IAC with this DBW setup?

Iat temps 150+ degrees Are you idling with the hood closed after the engine has been running awhile ?
Yes.
B3807 is set for 1.56% B4108 is disabled.
Already fixed those in recent tune. No change.
It seems like an AWFULL Lot of changes have been made in this tune. Not sure why as it looks like a mild engine.
Changed most values to the stock Vortec 5.7L specs.
Curious why you went with a DBW setup?
Definately appears to be much smoother throttle response to me.

Im not sure why this tune warrants so many changes from stock? Maybe it is better to start with a stock tune again, and go from there. Im sure the pro's will chime in soon for you.

Thanks for the reply!
June 18th, 2011
bvd80

Yes, stock MPFI spider.
June 18th, 2011
slows10

Ok I see. I opened the history tab and saw that list of changes. Im looking at the tune you posted. If B3807 and some other idle tables are fixed, why are they showing up on this tune?
June 18th, 2011
WeathermanShawn

Like Slow says..a lot of changes on this Tune. IMO, that always makes it harder to know where the problem is.

Obviously something is up with Bank1 LTFT's..I don't know whether that is from an exhaust leak or an issue with your O2's. It almost looks like HO2S11 and HO2S21 are reporting the same values..:confused: (at times). Normally there is an asymmetrical pattern to the O2's, and yours does not have it.

Check for an exhaust leak, change the O2s'..worst case go back to a stock tune and slowly add changes..

Thats my O2..:grin:.
June 18th, 2011
bvd80

Quote:

Originally Posted by slows10

Ok I see. I opened the history tab and saw that list of changes. Im looking at the tune you posted. If B3807 and some other idle tables are fixed, why are they showing up on this tune?

I think I posted the wrong tune...I did in fact correct those tables you mentioned though.
June 18th, 2011
bvd80

Quote:

Originally Posted by WeathermanShawn

Like Slow says..a lot of changes on this Tune. IMO, that always makes it harder to know where the problem is.

Obviously something is up with Bank1 LTFT's..I don't know whether that is from an exhaust leak or an issue with your O2's. It almost looks like HO2S11 and HO2S21 are reporting the same values..:confused: (at times). Normally there is an asymmetrical pattern to the O2's, and yours does not have it.

Check for an exhaust leak, change the O2s'..worst case go back to a stock tune and slowly add changes..

Thats my O2..:grin:.

I totally agree, but I sorta had to do this since there is no such factory DBW Vortec 5.7 tunes. Or, really, how much of a factory LSx tune can I keep stock to run the 5.7? I basically kept all things stock dealing with the 24x tables (ETC, spark dwell...), but most other tables came from the '02 Express van.

So how small of an exhaust leak would cause LTFT to go out of whack? I redid my exhaust and it's way better than it used to be before this conversion. I'm suspecting the wiring since I had to rewire a lot of it. I'll check continuity from the PCM to plugs and make sure the wiring is correct. O2s were brand new.

Thanks!!