Hi everyone,

I made a recent move and went from about 3000 ft to 5800 ft and my cold starts have been increasingly troublesome. I plugged in the laptop, fired up WinALDL and noticed something strange.

Engine coolant temp was about 107°F and as soon as I started the truck, WinALDL immediatly flagged "Closed Loop". It shouldn't be running in closed loop right off the bat. I believe I did lower the temperatures as to when closed loop can turn on, but what happened to the timer? Is there anything physical that can cause the ECM to start cold in closed loop or is it purely prom tuning?

Also after changing altitudes I'm running fairly lean. I saved the BLM tables from WinALDL but which one should I tune by? As the engine was cold, the BLM's were pretty much right on 128ish. As the engine warmed up they were all in the 112-114 range. The different tables that were saved are as follows:

Narrow Latest
Narrow AVG
Narrow Samples
Narrow AVG 10
Narrow Std. Dev.
Wide Latest
Wide AVG
Wide Samples
Wide AVG 10
Wide Std. Dev
Narrow Correction 10
Wide Correction 10

The wide latest table doesn't look too bad, but the narrow latest looks very lean. Which table should I be tuning by? I'm also guessing that to add fuel I adjust the MAF tables correct?

Thanks for the help.

-HD

 

As for the elevation change and running lean, that would be the BPC multiplier vs. barometric table. That is of course if the tune was correct before the move.

O2 sensor needs to be active before going closed loop.

RBob.

 

112-114 is rich actually (means ECU had to remove fuel to get to stoich). When the engine is cold, the BLMs are usually limited to 128 minimum, so don't trust them. Also BLM doesn't begin to update until the engine is a little warm.

MAF doesn't use BPC. During cranking with $6E, there is no Baro compensation, and that can cause excessively rich starting at high altitudes, and possibly flooding at really high altitudes. You may want to reduce the cranking PW by 10-15% at your elevation (should be near 82-83 kPa baro at that height)

How warm is it there, and was sun shining on the engine bay, and did you recently run the engine? 107°F on a cold start sounds a little warm for Canada.

Are you using a heated O2 sensor that heats during key on (while you were firing up your WINALDL or something? There's a few timer delays that need to pass before closed loop should start, if all things are normal.

 

Thanks for the replies.

To tell the whole tale, this is what happened this morning. I went out to change the oil, the temperature is about 72-73°F. I ran the engine for 3-4 minutes to warm the oil a little bit. Changed the oil. Hooked up the laptop, turned the key to the 'on' position while I check winaldl to make sure all is ok. I'm sure I had the key on before I started for more than 30 seconds which I believe is my hot timer, and my hot timer threshold is 104°F and the engine temp was reported as 107°F, so now I understand how I could have been in closed loop off start up.

And you're right about 112-114 BLM being rich, I don't know how I got those numbers mixed up. I will try reducing the crank PW and see what happens. I've played with this bin for so long it might be better to start again from scratch and log my data and changes more specifically. If you're interested in seeing my logs here is the file:

http://www.bcchardware.com/howdy/20060903.txt

I am considering starting from scratch and was wondering what you might recommend for a starter bin? I usually go with ARAP but I recently read one of your posts regarding the more tamer AUJM bin that might suit my setup better.

I realize this is a thirdgen board, but this is *the* place to go for diy prom help. I run a 5500lb 2WD GMC 1500 with this engine:

.030" over bore 350
54CC Trickflow Aluminum heads, 2.02, 1.6 with minor head work
Comp 280/280, .480"/.480" cam
Dished forged pistons
Hedders
Dual 2.5" exhaust with turbo mufflers
TH350 with shift kit and 2500 stall converter

MAF screens are still intact. I did disconnct the fuel pressure vacuum hose to achieve better idle and throttle response.

That's all I can think of right now, but let me know if there's anything else you'd like to know.

Thanks for the help.

-HD

 

Wow, brain fade on my part: "that would be the BPC multiplier vs. barometric table." Yep, no BPC on a MAF engine, or the need for baro correction. Please ignore my statement about baro & BPC.

I did note this in the last reply "I did disconnct the fuel pressure vacuum hose to achieve better idle and throttle response."

You should connect this back up, it is causing the engine to run rich. The purpose of a vacuum referenced FPR on a port engine is to maintain the same injector fuel flow across changing manifold pressure (or vacuum).

Without the vacuum line connected the higher the manifold vacuum the greater the fuel flow from the injector.

RBob.

 

I'm such a retard. I thought about that as I was typing it. I figured it'd be the first reply back too. Makes perfect sense though as fuel appears to be rich during low throttle. As you can see by the knock counts I need to pull some timing out, so I'll do that and take it out for another run and report back.

Thanks,

-Howdy

 

Especially with $6E MAF code, there's no way to make a disconnected vacuum referenced fuel pressure regulater run well.

I'm not on any crusade to dis ARAP and promote AUJM, but I usually end up saying that. I'm just biased I guess. I just look at the spark advance of ARAP and cringe, and pray that whoever uses it has an excellent knock sensor. That's my only real complaint about it.