What are some things that could cause my truck to not go into open loop?

[sixltrbtr]

2001 Silverado 2500 6.0L stock work truck

For a while now I've been noticing knock during hard acceleration. I was thinking my fuel pump was starting to get weak and since I've never changed it since I've owned the truck I went ahead and changed it. Of course the knock is still there so I get out the scanner and notice that it never goes in to open loop even with tps at 99%.:shock: What should I look for to remedy this issue. Anyone have any ideas? Thanks

[joecar]

Post tune/log files.


Measure rail pressure (with FPR reference hose disconnected).

Check PCV plumbing for oil.

[sixltrbtr]

Here is the tune

[joecar]

Logs...?

[sixltrbtr]

I don't have any logs to post at the moment and I didn't bring my laptop with me today so I will have to get them tomorrow. There is no oil in the PCV tubing and fuel pressure is 68psi with fpr unplugged

[joecar]

Shouldn't it be 58 psi...?

[sixltrbtr]

Hmm, yes. I will investigate this. Could this cause no open loop though? Fuel trims are perfect even with high fuel pressure...

[sixltrbtr]

Update: I have fixed the fuel pressure problem. I know have 58psi with reference hose disconnected. Truck is going into open loop under acceleration but still has some knock. Air/Fuel ratio stays near stoich. I just need to figure out now how to add more fuel to eliminate the knock.

[joecar]

Post log showing knock.

[sixltrbtr]

I have been pouring through the forums trying to figure out the best way to get my LM-2 connected to the scanner so I can log A/F and have decided that serial connection is the best way to go. I have a serial Molex cable ordered and it should come in one day this week. When I get that figured out and working I will make a log of the truck and post it. Are there any particular PID's you are wanting to see that would help you understand what is going on. Thanks again joecar for your input.

[joecar]

We want to see GM.EQIVRATIO and EXT.WO2LAM1 in addition to the usual pids (RPM, TPS, MAF, MAP, LONGFT1/2, SPARKADV, KR, ...).

[sixltrbtr]

Here is a log without wideband. Still waiting on the serial cable for the LM-2. First WOT knock was very audible. There isn't a saw tooth pattern but it does appear that timing is being pulled (although I'm not a pro at reading these logs). What is the GM.EQIVRATIO PID? Thanks again for the input.

[sixltrbtr]

Also, after looking back and studying the log I noticed the LTFT's adding 9+% WOT and I'm thinking that is probably not normal (not sure). Is this an issue?

[joecar]

With steady WOT throttle above 4000 rpm: use MAFFREQ to index the MAF table and bump it up a little in this area.

With WOT throttle below 4000 rpm: use MAP and RPM to index the VE table and bump it up a little in this area.

[joecar]

Reduce pid channel count to 24 (or less) to get faster sampling rate (i.e. better resolution)...

see "Selected Channels" at bottom of PIDs tab...

since we're going to use GM.EQIVRATIO for tuning, drop the pid GM.AFR, this will get pid channel count down to 23.

[joecar]

Do you have anything (exhaust pipe) banging anywhere (chassis)...?

[sixltrbtr]

Do you have anything (exhaust pipe) banging anywhere (chassis)...?

Exhaust is in good condition. There isn't anything banging. It is definitely spark knock that I hear and it logged it when I heard it.

[joecar]

In your log, KR coincides with TP going WOT, and commanded fueling (GM.EQIVRATIO) is only EQR 1.0391... this is way too lean for WOT (so you get knock).

( it actually steps 1.0195, 1.0391, 1.0195 )

When I look in your tune, I can't see where EQR 1.0391 is coming from.

[sixltrbtr]

Well the serial cable showed up tonight and I crimped the RJ11 connector on there and I'll be damned if it didn't work perfectly. It was easier than I expected so here is the log with the wideband logged as well.

[sixltrbtr]

Here is another log I made after adjusting the MAF on the upper end. There was a bobble in the transition but fuel came in much better where I made adjustments. I will have to figure out how to adjust the VE table to add fuel at lower rpm's now. I also attached the tune so you could see what I did to the B5001 MAF table.

Robert

[joecar]

ok, I'll look at your new logs shortly...

[joecar]

I see in your log that WO2LAM1 goes rich during WOT...

but I don't understand what EQIVRATIO is doing...!? And I see AFR matching/following EQIVRATIO.

[joecar]

Set B3643, 44, 45 to these values respectively: 1.00, 0.006250, 0.006250.

[sixltrbtr]

I see in your log that WO2LAM1 goes rich during WOT...

but I don't understand what EQIVRATIO is doing...!? And I see AFR matching/following EQIVRATIO.

Yeah, although I don't really understand what that pid is I was expecting it to do something different with the added fuel. Is it like the pcm's desired lambda or something?


Set B3643, 44, 45 to these values respectively: 1.00, 0.006250, 0.006250.

Okay, I will

[sixltrbtr]

Set B3643, 44, 45 to these values respectively: 1.00, 0.006250, 0.006250.

Ahh yes, I had messed with those. I will re-do the log now.

[sixltrbtr]

Does this look better? Still heard a little knock and looks like a lot more fuel than before. Maybe a little too rich in some places.

[statesman]

Zero all values in {B5908} Fuel Mixture Spark Correction.

[joecar]

Zero all values in {B5908} Fuel Mixture Spark Correction.I don't remember if B5908 adds or subtracts from sparkadv.

[joecar]

Does this look better? Still heard a little knock and looks like a lot more fuel than before. Maybe a little too rich in some places.
Looks much better...

where it's too rich: you can now edit B3618 PE table to reduce some of that fueling.
where it knocks: bring B3618 up a little (try EQR 1.175).

[sixltrbtr]

Thanks joecar! I will mess with it some more on Monday. After driving the truck around a little bit I can say that it already feels much better and seems to run stronger. I'm looking forward to tweaking the PE fueling to get it dialed in. I have noticed that it likes to knock while the truck is downshifting from a cruise. It feels like it's sruggeling to downshift quick enough or something. I'm wondering if adjusting it to downshift a little earlier would help some of that.

[statesman]

I don't remember if B5908 adds or subtracts from sparkadv.

Can be either.... Positive numbers add to spark advance and negative numbers subtract from spark advance.