Can't get 5.3 DBC swap to idle?

[RedLT4]

I recently got my 5.3 swap project started, but am having a hard time with idle settings. The cam is not that big(summit 8719-209 int./217 exh.) but my fumbling newbie attempts at this have failed so far.

Basically stock 5.3 bottom end with small compression bump(4.8 flat top pistons) cam mentioned above with an LS6 intake. Stock 5.3 MAF. I have the engine sitting in the frame(no body) and the wiring rigged up to run everything. Fuel pressure looks good 58psi. I am limited on how long I can let it run(no coolant yet).

Tried running through a few guides on doing this(setting base idle RPM and airflow values), and have randomly had it idle for a while, but on re-start, then it won't? I am able to hold the throttle open to keep it running and it sounds good when you blip the throttle(open headers). Tried different IACs and re-learns for this and the TPS, but no joy.

I understand that getting this dialed in can take time, but I'm worried I am missing something obvious about how to get it stay running at least. Tune and log file of my startup attempts attached. Please help.

[WAcord]

check out map sensor readings on the scan. that can not be right ?

[5FDP]

Yeah, the map should be around 100kpa sea level with the key on engine off. The log shows it in the 50's.

[blindsquirrel]

What's up with the firing order, won't this cause issues? Your '1st' is set to cyl #3, every other Gen3 tune I look at has '1st' as #1.

[RedLT4]

Good catch on the MAP, I had a 3 bar one installed for some reason.

MAP was swapped out, but it did not seem to make any difference. New log of some startup and idle attempts.

[RedLT4]

What's up with the firing order, won't this cause issues? Your '1st' is set to cyl #3, every other Gen3 tune I look at has '1st' as #1.

I questioned this too, but after some searching it seems some PCMs have this order weird for whatever reason. As long as the firing order is correct, it's OK.

[RedLT4]

Anyone have any suggestions on what could keep this thing from idling? What I should watch on the scan data while it's trying to idle?

[5FDP]

Nothing should really be stopping it. Unless you are losing fuel pressure while it's running or there is a major vacuum leak.

The camshaft and intake swap isn't that crazy, it should still idle on it's own.

For the hell of it, unplug the o2 sensors because they are useless at the moment anyway. You could even try starting it with the MAF failed in the tune or even unplugged to rule out a bad MAF.

It also looks like you swapped to 33lb/hr injectors, is that correct?

[RedLT4]

Nothing should really be stopping it. Unless you are losing fuel pressure while it's running or there is a major vacuum leak.

The camshaft and intake swap isn't that crazy, it should still idle on it's own.

For the hell of it, unplug the o2 sensors because they are useless at the moment anyway. You could even try starting it with the MAF failed in the tune or even unplugged to rule out a bad MAF.

It also looks like you swapped to 33lb/hr injectors, is that correct?

Checked it and the fuel pressure stays good while running. I haven't found any vacuum leaks. And yes, it has flex fuel injectors.

I unplugged the 02s and tried again this evening. I have no idea why it was different this time but it fired up at what seemed like a high idle then came down to 850ish(which is the RPM target) so I thought that's good. Unfortunately then if crept up to 1050ish for some reason? Had to shutdown before it got too hot. The only thing that changed really was the 02s but I am also disconnecting the battery each time I quit testing this for the day, so maybe it's loosing something?

Then I tried with the MAF unplugged, but idled way high. I think this one was mostly because my MAF has my IAT in it. On the plus side here, when reading -38* intake temps it was hitting close to 1050RPM which is the target at that temp.

Logs attached, but I'm still not sure what's happening?

[5FDP]

Stick a garden hose in the water pump neck and maybe take the thermostat out, that should let you run it a lot longer if you have water being pushed through the engine.

The MAF was just a test thing, it seems fine so keep it plugged in.

Another thing, you have likely removed the EGR so that stuff should be disabled. Use the navigator under the edit tab, go down to exhaust folder and disable the EGR switch. Then in the timing tables, zero out the EGR spark correction table. Also go into the coolant temp (ECT) base spark correction table and zero out all those negative numbers that are pulling timing away. See if you can't get the timing to stay around the 18ish degrees that is in the idle timing tables.

It may even require more/less base running airflow but it's really hard to say where it needs it when it's not a complete engine/exhaust and not everything is hooked up.

[RedLT4]

Stick a garden hose in the water pump neck and maybe take the thermostat out, that should let you run it a lot longer if you have water being pushed through the engine.

The MAF was just a test thing, it seems fine so keep it plugged in.

Another thing, you have likely removed the EGR so that stuff should be disabled. Use the navigator under the edit tab, go down to exhaust folder and disable the EGR switch. Then in the timing tables, zero out the EGR spark correction table. Also go into the coolant temp (ECT) base spark correction table and zero out all those negative numbers that are pulling timing away. See if you can't get the timing to stay around the 18ish degrees that is in the idle timing tables.

It may even require more/less base running airflow but it's really hard to say where it needs it when it's not a complete engine/exhaust and not everything is hooked up.

Thanks for your help. I mostly just wanted to make sure this thing was functioning, and now that I know, I think I may just move forward with the project and come back to the idle thing once it's all installed.

Speaking of, is it possible that this thing is having issues with idle due to there being no load on the engine whatsoever? No alternator, no water pump, power steering etc?

[bk2life]

Speaking of, is it possible that this thing is having issues with idle due to there being no load on the engine whatsoever? No alternator, no water pump, power steering etc?

no, it should still be able to fire up and idle

[RedLT4]

It's been awhile but just wanted to update on my idling issue. It's idling awesome now. Turns out the throttle body I used had a small hole drilled in the blade. I should have noticed this as many times I pulled the throttle body off

Oh well, the S10 Blazer project is close to going for a drive!