Failed Smog... tune?

[ferocity02]

Tried to smog the truck today and it failed, too much HC at idle. Results are:

Today: (Mods below)
HC: Max / Meas
Idle (720 RPM): 100 / 136
2500 RPM: 180 / 15

CO: Max / Meas
Idle (720 RPM): 1.0 / 0.21
2500 RPM: 1.1 / 0.01


2011: (Completely stock minus CAI)
HC: Max / Meas
Idle (572 RPM): 100 / 11
2500 RPM: 180 / 11

CO: Max / Meas
Idle (572 RPM): 1.0 / 0.06
2500 RPM: 1.1 / 0.01


Truck is an '01 5.3L Silverado (112k miles) with a 212/212 114 cam, unported 799 heads, stock compression. All smog equipment it on and working. Front O2 sensors were replaced 10k miles ago, and there is plenty of activity at idle. Stock manifolds and cats. Truck was plenty warm, fans are set to 215F on and 208F off. The tune is completely stock (for 4L60E) with minor some changes for the fans, DTC's for the T56 swap, and gear/tire size settings. I've driven with this tune for about 1.5 weeks so the LTFT's should have been good. No codes whatsoever. New air filter with stock intake. MAF sensor is clean. Brand new spark plugs. Truck runs great!

I can't say I'm surprised. I can smell gas fumes at idle...

So what in the tune can be adjusted to help with the HC at idle. Seems like it's just running rich?

A few ideas I have are to raise the idle speed. He said it has to be under 1100 RPM. Put some denatured alcohol in the fuel tank. And raise the fan temp settings. However I think these temporary solutions.

Because I'm running a 4L60E tune with my T56, it thinks it's in 2nd gear all the time. So perhaps the "In Gear" settings are causing it to be more rich than the "P/N" settings?

Any thoughts? Thanks!

[ferocity02]

I just made an idle log showing the O2 sensor activity. This is a hot idle at 700 RPM. LTFT's were 6.8%.

One thing that might be the issue is that I got a pending P0300 misfire code while making this log. There were no codes before I started. Perhaps this is the issue?

[joecar]

CL with cats should produce very low HC level... but, misfires can overwhelm the cats, exactly what you said.

[ferocity02]

CL with cats should produce very low HC level... but, misfires can overwhelm the cats, exactly what you said.

That's what I'm thinking too. I logged misfires on my drive home and only get them at idle, and the misfires were spread out fairly evenly across all cylinders. As soon as the RPM's picked up the misfires stopped except for one or two on the highway. Does this sound like a tune problem? This could explain why my 2500 RPM HC was so low, no misfires.

I'm thinking the RFAIG process might help some. And raising the idle and fan temps with some alcohol in the tank should squeeze me by. I just need a temporary solution at this point.

[Gordy M]

How old are you spark plug wires. Lately I ran a log on my 04 Escalade, 117000 miles and found LTFT where -8.6 and -0.7, ran a scan on misfires and #7 plug wire count was 86 and the others were 0. Put new plug wires on and now the are both less than -1.0.

[ferocity02]

They are originals. But the misfires are spread pretty evenly across the cylinders, so this tells me it probably not a single mechanical issue. But, I do have coils and new plug wires here to put on to try.

[ferocity02]

Changed the plug wires and coils today, still misfiring.

Also logged some data to do the RAFIG process, but I doubt that will help.

[Gregs]

Changed the plug wires and coils today, still misfiring.

Also logged some data to do the RAFIG process, but I doubt that will help.

Get some CRC MAF cleaner and spray down the MAF if you still have one.

[joecar]

Related threads (for my reference):

ls1tech.com->failed-ca-smog-too-much-hc-idle.html (http://ls1tech.com/forums/pcm-diagnostics-tuning/1631248-failed-ca-smog-too-much-hc-idle.html)

[ferocity02]

Got it to pass today finally...

HC: Max / Meas
Idle (804 RPM): 100 / 19 (was 136!)
2500 RPM: 180 / 13

The changes I made are as follows (in case someone has a similar issue in the future)
Used 91 octane instead of 87
Increased idle from 700 to 800 RPM (they don't check idle speed since it's automatically controlled, 800 RPM is much better for a manual anyways)
Reduced idle timing from 18 to 12 deg (supposed to give fuel more time to mix and increases EGT, they don't check timing since it's automatically controlled)
Raised fan on temp from 215 to 225F
Did some rough Calc.VET tuning using the LTFT's (idle was way off)
Dialed in idle desired airflow
Replaced plug wires and coils (to cure a misfire that I don't think was actually there)
Changed AIR pump check valves (driver's side was rusted shut, doesn't matter for the smog test though)
Ran 1 gallon of denatured alcohol with about 5 gallons of gas

The main fixes I think were in the tune since I was trying to use an auto tune for a manual. Thanks for the help!

[joecar]

Cool :cheers: thanks for posting back.