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Discussion Starter #1
Sorry to bother you guys with yet another problem but i would like to straighten this one out.

The other day i changed all GP's as per the other thread, at that time i removed my secondary fuel filter setup also and removed the GP timer that was installed.

I ran the truck and warmed it up, it ran just friggen great, i went to the car wash and washed off the engine bay, ever since its been stumbling like crazy at idle. Here's the scoop...

Starts great so far, idles wonderfull untill it gets up to temp, as soon as it hits a certain temp (170'ish) it starts to stumble, pretty much sounds like a cammed up gasser, i have the dual hi idles on a switch also, either hi idle and it still stumbles pretty good. Shut it down and unplug the coolant sensor and it runs just fine at idle, put it in gear with the sensor plugged in and it hardly stumbles, runs great on the hiway in cruise or on the peddle, just stumbling on idle by itself, the ECT sensor is clean as a whistle, fuel rate at idle is 1-2mm when it's stumbling, (which is always). Did i get something wet at the car wash??? If you put any load on it, it runs great. Fuel pressure is 6.75 lbs at idle and that was through 2 filters, now its just 1 filter.

BTW, these old tires make some nice smoke... :lol: , made a nice slippery J the other day.
 

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Sounds like its trying to go into TDC Offset learn mode...But if it was, and if it was staying there, then you would have tripped a 1214 Code.

Whats the idle fuel rate when its NOT stumbling? 1-2mm sounds a little odd...
 

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Man CR I hate to hear that; Lord knows you been thur a nuff already... The only thing I can say is if you ever want to come down south to Texas for a "get-a-way" I'll make sure you'll have room and board with me. Sorry wish I could help more:eek:: .
 

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Discussion Starter #4
I will have to check the fuel rate when its cold before it stumbles tomorrow and i'll also check with the ECT unplugged to see, let ya know then.
TDCO is -1.58 now, hasn't changed.
 

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NEED SOME MOVIES!!!!

I wanna see what a fueled 18:1 will do:D !
 

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Discussion Starter #6 (Edited)
NEED SOME MOVIES!!!!

I wanna see what a fueled 18:1 will do:D !
It will go like a mthr fker.... :lol:

But i really haven't pushed it yet. And remember its 7000 lbs!!

Edit: I weighed it today, 7560 lbs at the goverment hiway scale, half fuel load.
 

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What does your timing do when it hits 170F? If ACT is dropping to ~3.5 or atleast considerably lower than it was at 169, then its a TDCO problem.
 

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Discussion Starter #8
Can't see ACT numbers go there unless i run a time set command, it is always between 12-13 at idle on the AE scanner.
 

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CR
Your welcome to my Snap-on scanner...if that will help, sorry about not hooking up last week,(read the PM too late) if you were in the fort, you would have damn near drove past my house to get home, I'm on the east side of Edm. 137ave and Victoria trail
 

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It could be a short since washing the engine brought it on. ECT and IAT sensors are very sensative and reactive to volt surges, should be able to scan those values, try jiggling wires at ide with the scanner hooked up.
 

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Discussion Starter #11
CR
Your welcome to my Snap-on scanner...if that will help, sorry about not hooking up last week,(read the PM too late) if you were in the fort, you would have damn near drove past my house to get home, I'm on the east side of Edm. 137ave and Victoria trail
I was on Victoria trail at one point, I can't remember my bro inlaws address but i probably was within a couple of blocks of you but i don't know Edmonton very well at all. Then we were out at the Fort for a couple of hours too. If you have room in your shop i might be able to make it up there sunday for a few hours to check some stuff out?
 

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ECT and IAT problems would cause increase in idle fuel rates - CR indicated idle fuel rates of 1-2mm when 'stumbling'.

If high IAT\ECT caused PCM to reduce fuel, it would not do so at idle, but only at driving rpm ranges, where he indicates the engine runs well

In TDCO LEARN, PCM goes to backup mode and 1000rpm, which requires increased fuel rate over stock, which should be 7-10mm out of cold advance\fast idle

Best bet is to R&R all engine harness connectors and engine harness to PCM harness connectors, check for corrosion\oxidation\moisture.

Use the significant other's hair dryer to correct any damp situation.

Also check the main harness where it passes the lower AC tube into the firewall for chafing.
 

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I don't know if this will help, but I was/am having the same problem and it turns out it is the tps. I would have replaced it, but it was 5 bills so I decieded to clean it first, I did and it runs much better. I had the same problems with the temp too, it ran fine cold and warm, but 170ish wasn't good in traffic
 

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I don't know if this will help, but I was/am having the same problem and it turns out it is the tps. I would have replaced it, but it was 5 bills so I decieded to clean it first, I did and it runs much better. I had the same problems with the temp too, it ran fine cold and warm, but 170ish wasn't good in traffic
 

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Discussion Starter #15
OK, heres the latest scoop and thanks for the info GMCTD.

With the ECT sensor plugged in the truck will start to stumble when temps get above 180F, i thought earlier that it would run fine with it unplugged at that temp but it stumbles with it unplugged also above 180F, it stumbles on both hi idles above that temp also, below 180 there is no stumble on idle or hi idles. Fuel rates on the above info bounces from 0-2mm.

Now here's the funny part, pull the truck into gear so it won't roll and the stumbling appears to be gone and fuel rate holds steady @ 2mm. Even though the fuel rates are low remember i'm flashed for the 5068 pump @ 92mm so they probably arent representative of the actual fuel rate, that still needs to be adjusted by Westers to read correct rates, but its steady @ 2mm and no stumbling.

Here's something else i've found and maybe can be pointed in the right direction to fix it. When looking at the engine parameters its saying the ignition voltage is 25.5V, gotta be something wrong there, scanner reported correct voltage before on the ignition?

The scanner also display's ignition voltage in the tranny parameters and when reading it there its @ 13.7V. These reading must come from different circuits?

What can i do to trouble shoot the ignition to see why its reporting such hi voltages?

Here's a shot of the weather i'm working in so i'm not doing to much until i get home or to Nicks. lol
 

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Must be something in the IP - PCM monitors idle on a per-cyl basis, altering Fuel Rate to maintain steady rpm.

That per-cyl control is seen on the scanner as minor FR variation at idle.

Put a load on engine, as with AC or shift into any gear range, PCM alters fuel rate such that idle speed does not drop.

Now, it would appear as though the IP is over reacting to PCM idle control when not loaded, causing excess idle rpm variation to which PCM then over reacts, causing missing\stumbling, but smoothing out under load.

Could also be bad fuel, or cloudy fuel - don't know what type of problems were encountered, causing Stanadyne to discontinue that 5068 IP

TDCO looks good, so maybe you should just drive it for a week or so - don't tweak or relearn, don't mess with the mix - let driveability parameters soak in .

Don't let it idle in Park or Nuetral for the next week, since it smooths out when in a gear range, and keep an eye on trans temps
 

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Discussion Starter #17
What about the 25V ignition reading?
 

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What about the 25V ignition reading?
it's doubtful but your batteries are hooked up correctly aren't they. in parallel or in series. one would give a reading of say 12.? volts or 24.? volts.
 

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Discussion Starter #19
Everything else reads +/-13v both with the scanner, the dash gauge (14ish) and the inverter i use.
 

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Flux invertor? I thought you had a flux convertor.
 
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