Closing in on a problem

**ony** · 09-18-2014

that was a short log, get some hyway log time you might try the chip eagle mark adjusted and see if it is closer. the blm proble go up as you are driving most chips I have had in my v6 would have blms in the 140's till I changed the ve table. also 4.3 v6's run a higher scotck number .512-.540 instead of .451 like v/8's for some reason. when the egr is called for it will cut the pulse with down causing blms to raise . it is proble in the tune int. trying to take away fuel, blm trying to add fuel I only seen a short idle log.

**ony** · 09-19-2014

if you will get a long data log and post it I will try to make you a starter chip and send it to you from a bin I found. my v6 is a vortec in a 91 model which they didn't make. I have had better luck with a 288 ecm be cause I am not a pro tuner. I will send you a chip if I can find a 2732 that I can erase and reprogram. I have several of these. my truck is a standerd trans so I would be tunning blind if you are interested post a data log and give me your mailing address in a personal e mail or message on the gearhead sight. how many rpms do you want it to idle at, are you running a cat, are you running the egr, what part of the country are you located so we can set open loop fuel an spark.

**1great40** · 09-20-2014

Thank you for the offer! I did get under the truck tonight to get a better read on the fuel pressure. Turns out it wasn't as high as I thought. It took me about an hour to come up with a small tool to get into the screw of the pressure regulator but I have a solid 12.5 to 13 PSI of fuel pressure now. The idle is better than ever and the idle speed came up some too. It's idling at a solid 600 RPM in gear now, that's where just about every GM V6 seems to idle and the idle quality is pretty darn good. This is the type of outcome I have been looking for... just getting the engine to run correctly with a stock calibration. As mentioned, I didn't want to "mask" something by tuning. Of course there's nothing wrong with a good tune, but the engine should be running correctly to begin with. I will run it like this for a while, then do another data log. I'm not sure why the last one was so short, pilot error I guess. It will be interesting to see where the BLM number settles in at and whether or not the engine needs a custom PROM once I try the dual exhaust again. There's still the typical V6 vibration at idle, it's just very slight, but this is not a balance shaft engine and possibly a RPM recalibration will be in order in the future. Stay tuned... (no pun intended)

**ony** · 09-20-2014

glad to hear your getting good results.

**1great40** · 09-21-2014

I drove the truck around quite a bit this morning, this is the best it has run since it was first out into service. To be cautious, before there are any other changes made, i plan to do another data log and check the BLM value. If it's good, then I need to decide what to do next...do I try the chip Mark made which sets the idle to about 700 RPM and that should eliminate the little V6 vibration and call it a day? Do I leave the chip stock and try to up the fuel pressure just alittle more to allow it to run OK with the dual exhaust or do I attempt to have a chip made which encompasses the changes that Mark made (higher idle, no EGR, AIR and Purge) plus an altered fuel table or VE table or whatever the correct name is to allow the Fuel pressure to stay under 13 PSI. Right now it's just under 13 PSI.

Thanks so much for everyone's help.

**ony** · 09-21-2014

if it is running pretty good I would get a data log and see where you are at, it takes several restarts from a cold engine to fully warmed up for the ecm to finally diciede if it is done programming all it can program. it may get smooth as silk or go the other way after it is run a few times.

**1great40** · 09-29-2014

Put about another hundred miles one truck today. The check engine light came on but reset itself when I restarted the engine. The truck is running really well and there is evidence of black in the one active tailpipe. I'm going to do another log tonight hopefully the BLM number is in a good range. I think a new chip is in order though, I would like to raise the idle by about 50 rpm and disable EGR, AIR and purge. The chip I have from Mark does all that stuff but the idle is 725, the current stock idle is about 600. Once I'm sure that the lean condition has been addressed by the fuel pressure change, then I think I need to try Marks chip again.

Another thought, if the BLM is below 128, would it make sense to switch back to the dual exhaust and see what effect it has on the BLM value?

**jim_in_dorris** · 09-29-2014

If your BLM goes below 120, and you are getting soot in the active tail pipe, I would definitely try full dual exhaust again. At least get some data logging in to see where you are at.

**1great40** · 10-03-2014

I ran the truck out to a cruise night tonight and when I got home, the CEL was on. I fired up TunerPro and did another data log:The CEL was an EGR error, which I think will go away with the modified chip. The BLM was encouraging at 130-133. The bump in fuel pressure certainly did get it richer. I'm thinking of making the pressure just a little higher and trying the dual exhaust again/ What do you guys think?

**dave w** · 10-03-2014

Originally Posted by 1great40

I ran the truck out to a cruise night tonight and when I got home, the CEL was on. I fired up TunerPro and did another data log:The CEL was an EGR error, which I think will go away with the modified chip. The BLM was encouraging at 130-133. The bump in fuel pressure certainly did get it richer. I'm thinking of making the pressure just a little higher and trying the dual exhaust again/ What do you guys think?

I like that plan.

dave w

**ony** · 10-03-2014

I would try eagle marks chip , if the egr is disabled it will bring blms down in places the the egr is called for, it sounds like your closing in on the problems.

**steveo** · 10-03-2014

130-133 is close. that's skew a couple percent at some kinda fueling constant or table and call it good. that difference could even be from an unaccounted for percentage of ethanol in your fuel or something like that.

you want to get it the other direction, though. 123-125 or so. then fine tune it to try to get it closer if you even care (you shouldn't)

**1great40** · 10-20-2014

Hi all. Today I installed the PROM that Eagle Mark cooked up for me, just to see how the truck would run. The good news is that it runs exactly like the stock PROM. The bad news is that it runs exactly like the stock PROM. The whole point in having the custom PROM was to have the idle set to 725 RPM. I know he addressed things like EGR, AIR, etc but I was disappointed that there is no change in the idle speed. I'm not sure what I'm missing here. What sort of magic does it take to change the idle speed? The odd thing is that when I first tried this prom, I was observing the RPM with an Actron scanner. That scanner only works in 10k mode. Mark told me he defaulted all the idle values to 725, that included the idle speed in 10K mode, which is usually 1000 RPM. When the scanner was attached, the engine idled at 725 RPM in park and 725 RPM in drive.

Anyone have any suggestions?

**dave w** · 10-20-2014

Originally Posted by 1great40

Hi all. Today I installed the PROM that Eagle Mark cooked up for me, just to see how the truck would run. The good news is that it runs exactly like the stock PROM. The bad news is that it runs exactly like the stock PROM. The whole point in having the custom PROM was to have the idle set to 725 RPM. I know he addressed things like EGR, AIR, etc but I was disappointed that there is no change in the idle speed. I'm not sure what I'm missing here. What sort of magic does it take to change the idle speed? The odd thing is that when I first tried this prom, I was observing the RPM with an Actron scanner. That scanner only works in 10k mode. Mark told me he defaulted all the idle values to 725, that included the idle speed in 10K mode, which is usually 1000 RPM. When the scanner was attached, the engine idled at 725 RPM in park and 725 RPM in drive.

Anyone have any suggestions?

The TunerPro parameter search shows about 20 idle parameters for the '7747 ECM. See attached screen shot. Usually the Desired IAC Idle C/L (closed loop) Speed table has the biggest effect on idle speed. I recommend an IAC minimum air adjustment of 10 ~ 20 steps prior to PROM chip changes.

dave w