Lean Condition and High Idle in Swap Vehicle

[runpasthefence]

Hey guys, first post, but I've used these forums for a lot of info in the past. I've been spinning my wheels (figuratively) with my 1950 Chevrolet swap for a while now. I'd appreciate some other perspectives and any advice you guys might have. Writing all of this stuff out helps as well.

Stats:
2003 LQ9
Magnacharger MP112
LS6 Cam and valvetrain
61lb/hr injectors from FiveO
87mm truck TB
4L80e
New PSI Conversion harness

History -
I previously installed the LQ9 in my C10 and it ran well. It was stock aside from headers and a tune back then. The engine hasn't run correctly since modified.
Originally ordered a tune via mail-order service hoping it'd run well enough to drive the truck to a dyno-tune shop. When the truck didn't idle correctly, I bought HP Tuners to see what's up and see if I could remedy it myself. I noticed a couple of things, but the truck still doesn't run reliably.

Situation -
Currently, the truck starts and idles high (1500-1900rpms) and LTFT on both sides are around +25%. RPMs hang up and take a long time to reduce if any throttle is applied.
I've been unable to find any vacuum leaks.
O2 sensors are new, and the same readings are coming from two different sets.
MAF is new, but I have a hard time trusting any MAF old or new from past experiences.

That's all I can think of now. I'm attaching my most recent tune and log file. I'd be interested to see if anyone can glean any relevant information from the attachments. Any input would be greatly appreciated.

note- Ignore AFR readings in the log. I'm having a hard time getting the PLX wideband to read as a pid.

Thanks guys.

[runpasthefence]

Tried to find vacuum leaks again today. I used carb cleaner instead of ether this time. I thought the high idle might've hidden the engine's response to ether. I emptied a whole can of carb cleaner around anything and everything that could produce a leak, and I got nothing.

One thing I did find - I tested the resistance on the chassis ground from the PSI harness. It reads within spec with the ignition off, but as soon as I turn the ignition on it jumps to 50ohm. I made a jumper to go directly to the battery and I retested and came to the same result. The rest of my grounds ohm out perfectly.
This is similar to a condition I noticed in my old junkyard harness. It's part of the reason I bought the PSI unit.

Could these symptoms add up to a fried PCM? I have a tune that's trying to command an idle at 850 or so, but it idles at 1750 or greater. I have grounds coming from the harness that jump in resistance with ignition on.

Any input before I drop some $ on a PCM to test?

[Road]

I would check your ground resistance at the ecm connector disconnected might help if you posted your tune so it can get reviewed

[nkautz]

Your maf and your wideband aren't working. The values aren't changing at all in your log.... They should at least be bouncing around a bit

[runpasthefence]

I would check your ground resistance at the ecm connector disconnected might help if you posted your tune so it can get reviewed

I'll pull the connectors and check that. Tune is in first post.

Your maf and your wideband aren't working. The values aren't changing at all in your log.... They should at least be bouncing around a bit

Hadn't noticed the MAF. It's brand new, but I guess that doesn't mean anything. I haven't been able to get my wideband to read since it was installed. I think that's another issue entirely.

[runpasthefence]

Checked pins at PCM. All were less than 1ohm.

Plugged in an old MAF, and I'm still seeing .21lb/min with zero fluctuation. Something is screwy there.

[DRTurbo]

Is this truck the type that has a separate maf and IAT? I would love to try and run the truck with no MAF input, but if it idles at 1600 with a "closed" throttle then I would suspect leak. Throttle doesnt go below 1%, if the throttle isn't correctly Zeroed that might be enough to cause it to come up, but the RPMs seem like they fall smooth - but your throttle is slow returning with them, it doesnt snap back. If this is a cable throttle i'd say inspect the blade and make sure its closing correctly ( and isnt drilled ) as well as inspect the cable to make sure its not getting caught up when it attempts to return. GL

Doc
Counts Kustoms / VPT
Las Vegas- NV

[C5 2000]

Return MAF Cylair Maximum vs RPM back to stock to solve High Idle problem.

[runpasthefence]

Is this truck the type that has a separate maf and IAT? I would love to try and run the truck with no MAF input, but if it idles at 1600 with a "closed" throttle then I would suspect leak. Throttle doesnt go below 1%, if the throttle isn't correctly Zeroed that might be enough to cause it to come up, but the RPMs seem like they fall smooth - but your throttle is slow returning with them, it doesnt snap back. If this is a cable throttle i'd say inspect the blade and make sure its closing correctly ( and isnt drilled ) as well as inspect the cable to make sure its not getting caught up when it attempts to return. GL

It's DBW and, as far as I can tell, the blade is closing completely. The MAF has the IAT built in, but I've spliced in an auxiliary IAT for the blower manifold. After talking with PSI, it looks like I wired the IAT wrong. The pinout from Magnacharger doesn't match PSI. I'll fix that tomorrow and see what that affects.

Return MAF Cylair Maximum vs RPM back to stock to solve High Idle problem.

I'll take a look at that tomorrow, thanks.

[runpasthefence]

Good news: fixed the IAT and MAF sensors. My high idle is gone and my MAF appears to be reading correctly (approximately 5lbs/min @2000rpm).

Bad news: Engine now won't idle. It surges pretty heavily.
It's still running quite lean. I saw +50% on STFT. I noticed on the scanner that my throttle body reading was constantly 18-25% (can't remember exactly, log attached) even without any pedal input. I tried a TB reset, but I get the same thing.

Anway, I've attached the log. I should mention that I can only view my logs at my shop as I don't have a Windows computer at home or at work.

Thoughts would be appreciated.

[runpasthefence]

Forgot the log - here it is

[C5 2000]

Compare with stock file see if you missed something with the DTC, and use Russ Idle-Airflow.cfg.

[C5 2000]

Also set your Dynamic Airflow back to Stock.

[runpasthefence]

Compare with stock file see if you missed something with the DTC, and use Russ Idle-Airflow.cfg.

Also set your Dynamic Airflow back to Stock.

Meant to get on that this morning, but I don't have the stock file, and I don't have internet at the shop. I'll track one down in the repository and see what comes up.

[DRTurbo]

That st ft isnt right but an input of 18-25% at idle is 100% normal for an etc car. Thats how they idle

[C5 2000]

Stock 2003 Silverado

[runpasthefence]

Found a stock LQ9 tune just in case the 5.3 was different. Set dynamic airflow back to stock and saw no change. I downloaded RussK's idle airflow configuration, but it's useless unless the engine will actually idle. I've attached the log file for those running attempts after resetting the dynamic airflow.

stockdynamic.hpl

I brought my shop computer home with me and plan on going through the stock LQ9 tune to see if there's anything that stands out as abnormal in my mail-order tune.

[runpasthefence]

That st ft isnt right but an input of 18-25% at idle is 100% normal for an etc car. Thats how they idle

Yeah, I've never seen short term fuel trims that high before. +50% seems very strange. What's at work here?

[nkautz]

I would take a stock lq9 tune , flash it in and go from there. If you get your wideband working , it will be easier to diagnose. It's probably just not configured properly in the scanner. What brand is it? I tuned my car and 85% of the tune is stock, it's running great. It's an LQ9. SD (no maf). The IFR , VE , and spark tables are scaled by 1/2 because it was exceeding airflow limits and going into REP.

Take a look at my tune compared to a stock one just to get an idea of what tables need to be changed. It's a lot less than you probably think:

[runpasthefence]

Thanks for the data. I've been doing exactly what you recommended today. I've been blending my mail-order tune with the stock tune to create a new "square 1." I've been studying the MAF/SD debate, and I might play with an SD tune while I'm at it. I've already got a 2bar MAP at the shop.

Once again, thanks for the hard data. Discovering the compare tool has been great for learning.

edit- I definitely need to get the wideband going. Sent PLX an email and haven't heard back. I configured it myself a couple of times to no avail, and then I used the one stored in the scanner, and it didn't make a difference. It's not something I've spent a lot of time on, but I'll go through it soon.