2005 H2 LQ4 idle timing quick drops and surge

[GearHed86]

Hello all, have a vehicle here that has been acting odd at idle intermittently and trying to iron out the tune to fix this. In short the vehicle has a ProCharger, LS3 heads, Aftermarket intake manifold, cam duration 228/232 @ 0.050. I started with a 100% stock tune so didn't have any prior changes in question. I have spent hours going over this thing and all around runs well and I have put 100 miles or so on it so have plenty of timing logging and fine tuning. Wideband VE and MAF and PE tunes then everything back to running on fuel trims. STIT and LTIT idle trims will stay within about 1%, although it seems even at same engine temps after a long drive it starts adding more for some reason I haven't found yet.

The main issue I have stumbled across and cannot find an answer anywhere is this- When slowing to a stop and at a stop in gear the timing idle will sharply drop from a fairly solid 24 degrees where I have it set down to 6 degrees and will almost instantly shoot back up. Its like some sort of diag test cycle. It will do this 2 or 3 times then steady back out. I can put the shifter in Park and within a few seconds it does the same thing there and stops. Back into gear and it does it again, 2 or 3 drops down to 6 degrees and instantly goes back up and holds steady. I think the truck has always had this issue but with everything else holding well in the tune this started sticking out more and is causing the engine to about die and bounce back. I have gone over every spark or timing related table and have 24 degrees set across the board to not give it a number to drop to. I have idle adjust spark rpm decrease set to a max of -2 degrees to rule that out. I have disabled CAT tests at idle to test a theory and that didn't change either (the vehicle does have catalytic converters and sets no codes for anything related to them). I'm not sure what else to try to get this to stop but just can't find a reason for the pcm to command this behavior. It's not a choppy idle or any problem at all. I have the idle rpm at 750 in Park and 800 in gear and holds there just fine. Fuel trims are +/- a few % of 0 across the board.

Has anyone ran into this or have a solution to prevent these odd timing dips? Thoughts and help much appreciated, thanks.

[edcmat-l1]

Hang on y'all I got this......

businessman-looking-into-crystal-ball.jpg

Post a tune file and data log so we can actually see what's going on.

[GearHed86]

Ok great thanks for offering to take a look.
Here is one of the last scans I did on it after I disabled the idle CAT tests. I made some minor MAF # changes on this flash too so they aren't as steady as on longer previous drives but this was just to try a few different things.
Go to the 10:47 time in the scan log and from there until the end is when I sat and went between Park and Drive. You can see the cycle happen by watching the timing line drop and come back up. I don't have a HPT tune file sorry, I have been using another editor on this vehicle so only have HPT scan but can read it with HPT later if needed.

H2 Idle timing drops 1.6 121723.hpl

[edcmat-l1]

If you're scanning with HPT you have the ability to read out the file. I'm pretty sure it's going to be something in the idle control but without seeing the file can't say for sure.

[GearHed86]

You bet, thats why I offered to read with hpt. Current tune attached. Timing tables were all toyed with on low end to try to rid the timing drop. Once that is fixed I can finish smoothing things out with this tune! If its an idle delay table or something related that would be great to know! It's been years since I've had a DBW LS vehicle to tune so lots of freshening up and relearning on this one, just never ran into this. Using HPT is worlds faster and easier since scanner is plug and play but I didn't have support for this one yet so had to go a different route. I'm here to learn and why I asked, just an odd one I've not run into yet. I have been reading and watching a lot of videos for this one. Please let me know if you see anything that jumps out to try, thanks.

[edcmat-l1]

Lots wrong with the entire calibration.

VE looks terrible. Can't be right.

MAP linear and offset aren't correct for the vehicle's OE map sensor. And they aren't setup for a 2 bar either.

MAF table is basically doubled. Why is that? Either injector data is wrong or no fuel pressure, etc.

Only thing changed in injector data is the flow rate which means everything else is wrong.

Too much idle timing.

Idle over/under spark tables are effed.

The throttle angle looks way too low in your data log which leads me to believe the BOV is closed at idle. Should be open.

Several things lead to it idling up right before the timing tries to pull it back down.

Basically, wipe it out and start over with sane input.

[GearHed86]

Yeah the VE is a mess now looking at it on HPT for sure. This engine has an LS3 1 bar (or 1.5 bar as some call it) map sensor because of the intake. I didn't know until after doing a lengthy WB VE tune that was smoothed over and looked nice on the 3D map. The original table went out the window because I only did a quick stft learn a few times to get it in the ballpark after I learned of the different MAP sensor settings for this sensor. Timing as noted was lots of throwing things at the wall to see a change and then fix it, but sounds like easier to start over and I don't disagree. The timing dip occurred prior to correcting the MAP sensor so wasn't on the priority list until I found a reason idle is doing what it is doing.
Injector data I will have to investigate. That's what came in the door with this vehicle, not running, and I didn't get any info so is the only thing that carried over and what I started with. That explains a lot of other things though. I'll see if I can get more injector info and address that- then redo the rest since that effects it all.

BOV I have no idea what was done outside of the installer following the installation guide- BUT I will say a few others tried to tune this vehicle and owner said it just felt like it wasn't making the power it should have. I only got it for fuel system work and that turned into Hey this thing needs tuned.
I know 10 people will say 10 different ways to tune. I am here to learn and want to do this the right way and why I asked for help.
Thanks for the insight. I will post back with new tune in a few days.

[GearHed86]

Fuel injector data found, forgot they sent me some info on them so I hope this helps. Fuel Injector Clinic ave flow 518cc/min at 3 Bar. I have the voltage offset also so I can enter that.

One question I have - this vehicle is a return-less fuel system so runs at 58psi all the time. I wasn't sure why the previous tuner had scaled numbers in the tune but is just what was there to start with before I had any injector info so plugged it in to have something to start with- guess that was a mistake! Has been a lot of learning on this vehicle to say the least.
So for the injector data - the stock file is not a fixed number either. I have not seen a return-less fuel system file for these to know any different as this isn't my wheel house. I have the injector spreadsheet to plug numbers in to start with. Should I be using a fixed number across the IFR vs KPA table since this runs a fixed 58psi? Since thats the base of everything I'd like to make sure its correct.

[edcmat-l1]

If they're FIC injectors they should have an entire spread sheet with copy and paste tables.

[Alvin]

Why not use a 2 bar sensor? Why not a 2 bar OS?

This tune is a real mess. Honestly. Idle timing is also way too high. Shoot for around 15-18 degrees.

[edcmat-l1]

I know 10 people will say 10 different ways to tune.

10 different competent tuners will all tell you the same thing. It should be tuned with mathematical accuracy and sane values. That whole "different ways to skin a cat" thing is just a way of saying I don't really know what I'm doing.

[SiriusC1024]

Fuel injector data found, forgot they sent me some info on them so I hope this helps. Fuel Injector Clinic ave flow 518cc/min at 3 Bar. I have the voltage offset also so I can enter that.

One question I have - this vehicle is a return-less fuel system so runs at 58psi all the time. I wasn't sure why the previous tuner had scaled numbers in the tune but is just what was there to start with before I had any injector info so plugged it in to have something to start with- guess that was a mistake! Has been a lot of learning on this vehicle to say the least.
So for the injector data - the stock file is not a fixed number either. I have not seen a return-less fuel system file for these to know any different as this isn't my wheel house. I have the injector spreadsheet to plug numbers in to start with. Should I be using a fixed number across the IFR vs KPA table since this runs a fixed 58psi? Since thats the base of everything I'd like to make sure its correct.

Post the injector data. I'll show you.

[GearHed86]

Yes tune posted is a mess. Yes I know things were wrong. Tune when I got it was a mess as there was a 3 Bar LS3 map sensor, wired and tuned wrong at that, and others gave up instead of troubleshoot. LOTS of junk thrown at it to fix an intermittent idle stall issue that came and went. Idle would be fine for days then act up. The timing tables are all jacked for a reason- it wasn't to leave that way nor is that how they were, it was to help find where an issue was and I ran out of things I could see and why I posted here for help. I'm embarrassed I even posted it knowing I would get smeared lol and deservedly but was asked- again I need to do this CORRECTLY and why I'm here asking as I want this right. It's been a learning process for sure as I don't know much about the LS pcm world. I watched the ChopperDoc videos to get base dialed in and read idle pointers on here. Ed pointed me to a few things I hadn't looked at.

I have the correct injector data now so we are set there and I was ready to flash a new file to work on the VE map from a clean slate.
On to the new found issue! I just had a chance to get to this vehicle again and have suspected something wrong with the surge valve (BOV if you will) so I popped off the fender liner to get to it. It tests ok and was installed properly. I went to put it back on and noticed the hose from the outlet of the supercharger disconnected! Appears to have been this way a long time. Also explains the loss of power concern prior to me getting it. Had Ed not mentioned throttle angle at idle and asked about BOV I wouldn't have investigated. You can't see it from the top of the engine bay and the tube looks fine from that view. So NOW I can start with a sound intake tract and get this tuned properly.
Thanks for the insight guys, I will report back after tuning.

[GearHed86]

Hey guys I have a bit of an update on this vehicle. This was a fresh build prior to me getting it and everything from heads up is new. After addressing the supercharger hose and starting with a clean slate tune file I did two 5-10 mile drives for initial VE tuning now that I have correct MAP values and injector values. Runs like a completely different truck now. Ed you mentioned one thing that has stuck with- the throttle angle. I just don't have experience with DBW LS vehicles in regards to custom tuning the engine side so something I've never paid attention to until you brought it up. After my first VE adjustment and 2nd drive I noticed at idle the throttle angle only being around 3-5% in gear. This is with a slightly raised idle for the cam so I stopped. No reason to go any further on tune because that didn't seem correct. I searched a bit on this forum and seems a stock vehicle may be in the 5-10% throttle range at idle and a modified engine slightly higher so that told me there's leaks. I sprayed each bank of the engine around the injectors and intake runners and could immediately watch fuel trims pull fuel. This vehicle has an aftermarket LS3 fab'd intake and matching fuel rails. I sprayed soap water around all injectors and put some air to the intake and got bubbles from all injectors where they go into the intake. I opted to pull the intake manifold to inspect those seals too and good thing I did- import junk! The seals were black rubber and already swelled up larger than the groove! Installer said they came with the intake and why question new seals that came with it right? So I ordered new seals. Then also discovered a PCV hose going to a port on the intake that was wide open on one end. That all added up to a lot of air getting in behind the throttle body. All things that shouldn't have been but were- and adding to frustration on odd idle behavior and tunes not making sense!

Today was the first chance I had to work on new tune and drive with all the leaks fixed so I wanted to post this because with all the above changed- its still doing the exact same thing at idle in gear. It did it with a 100% virgin tune with MAF disabled, after 4 VE tunes, and now I am doing the MAF only logs and same results. At idle in gear after a short time it will briefly pull all timing and go right back, then a few seconds later do it again and stays put maybe 10 seconds and runs this again. I cut the idle overspeed and underspeed timing tables about in half and made no difference. It seems in Park it doesn't do this, only in gear and at any speed OFF the throttle under about 10mph or so, so isn't only sitting stopped. I don't have any scan logs on this computer but can post later if needed, you get the idea what its doing. Throttle angle is around 10-13% at idle now. With the world of changes and mechanical corrections this has been through the idle timing drops have remained from the start.

[edcmat-l1]

Post the current tune file version and corresponding data log.

[GearHed86]

Here are some logs I did earlier and a variety to see various things. One scan is a VE log after some smoothing, one is a MAF only log, and the last is a short Idle log- which was started without shutting the engine off from the MAF only log. A few of the numbers in the data froze near the end of the MAF log and didn't look right so is the reason I did this. In all of the scans, tail end of the VE and MAF logs, you can see the timing drop at idle in gear and keeps running on a cycle as noted. In park it still does it but isn't as noticeable since the engine doesn't have a load on it.

Ed- I am using TunerCat for the editing on this vehicle. It's not the easiest getting the pcm out to bench read due to the supercharger and pcm relocation bracket. It hasn't been the easiest using HPT to read files in the vehicle to say the least and seems every time I have to go back and pull more fuses. I have schematics for all the data buss and fuses, is just something Im not crazy about doing every time to read it with HPT so I apologize for the delays in posts.

To re-cap on the tune: I have done only basic things so far. Injector values, Idle rpm raised a little, VE table, MAF table (both adjusted using STFT), 24 degrees of timing at low rpm and low load cells but otherwise stock timing tables. A few other small changes. I didn't want to do anymore than necessary to try to mask something. I have NOT re-installed my WB for heavy and WOT fueling as that isn't a concern until I sort out the idle timing drops. I have driven the vehicle a lot just in VE configuration to get close on the VE map in the tune. TC doesn't have as nice of a 3D view and options to smooth so what looks nice on there isn't the same on HPT. My VE log shows where the STFT #s are at on the map and everything within 2-3% (other scans go up higher in RPM than the attached file with same %).

I will add this- since I fixed all the intake leaks and started over on the tune the engine has never stalled or acted like it wants to. Maybe I'm just being too picky lol, I'd just love to know the reason for these timing drops at idle and so the owner doesn't question it having that feeling. Even before the engine upgrades it has done this with a few others tuning the vehicle and I'd love to iron this out! Thanks again for your time looking at this.

[edcmat-l1]

What injectors are in it?

Need to make another pid list. Get rid of a lot of what you have and add as many timing advance pids as available. That should tell you exactly what's making it dip.

[GearHed86]

Thanks Ed good call, I like lots of data but apparently just not enough in the right place. I made a new PID list to watch more timing advance data and caught the culprit. Torque Management was causing it, commanding upwards of -20 degrees on those blips.

I found several other posts on various forums about this exact issue. Most of their solutions were to go into System Options and set Brake Tq Management to a "0" if it had a "1" (on 4L60E models). This file already was set to 0 from the factory. This H2 has a 4L65E not a 4L80E which seemed odd but maybe just how they are. I went to the Max Allowable Spark Retard vs RPM table (maybe called something similar in HPT) and zeroed the lower RPM cells and that got rid of the timing dips at idle. FINALLY I can move forward on this and send it on its way! Thanks again for the help

[edcmat-l1]

I was thinking it was some sort of TM. Shouldn't have been idle control. Glad you found it and fixed it.