GMC HAULER? Scanner/TDCO???

[rjwest]

Downloaded Carcode software, Cylindr balance and other test included.

Cylinder Bal test, Gives control & Within Limits
Responce, Can hear eng miss.

TDCO Test. I enabled it and TDCO went from -1.1 to -2.5 ( I think I csrewed up ) can you enlighten me on how test is supposed to work?

Carcode has a Line entry for test, highlite and
than check enable block. Of coarse no directions on how to use the program....

Eng idles smother, more snap, and some ping when rolling into throttle. Big differance above 2500 rpm..

Here are the pre/post screw up parameters:
at idle 600 rpm

Parameter Before After
TDCO-offset -1.1 -2.5
IPT-Inj pmp timg sig deg 9.5 4.2
IPT desired 9.5 9.3

When I get on it and rpm increase the IPT
jumps up around 9-10.degrees....

Is -2.5 to much?????

[GMC Hauler]

I think +/- 2.5 is where the PCM will set a code. -1.94 is of course, the board recommendation. I run a little less to keep the rattle down. Some people here run -2.02. It's your choice. All the other specs you gave match with what I've seen with the Autoenginuity scan tool. Probably just need to adjust the TDC offset.

Kennedy stated once that you can play with the gas pedal to help adjust for a different TDC offset. I've tried it several times and it works. Run the learn command while playing with the pedal.

[rjwest]

Tried the gas pedal 2 times , no change,
It does set code, P1214,
Really big differance. When the boost comes up, timming advances and it's a real kick
in power, almost like a 4 barrel kicking in..
Also Jumps with just a tap of throttle in 1st gear..

I think I will try the book procedure ( key on/off thing ) tommorow, and see if it relearns a lower setting. realy hate to set it back, but probably not good for motor running with a load...

How was your trip, ????

Can't call carcode, he's on vacation,

[GMC Hauler]

Trip was real good. Learned alot about driving with a large trailer and heavy loads. My nemesis the entire trip eas EGT. I need some intercooling. I learned that if I drive faster (got it into overdrive and ran about 70 mph) versus driving in direct at 55-60 mph, I kept temperatures under control to include EGT, transmission and engine.

I figured out that my lift pump pressure gage is a great way to gage fuel usage between gears, and that overdrive really does use less gas while towing. When fuel pressure was higher, I was using less fuel. Gas mileage was not great this trip. I got 9 mpg. I was careful about using the torque converter locked in overdrive with that large load. I increased line pressure while using overdrive, which really makes the case for in cab transmission line pressure adjustment.

I saw alot of neat sights in our great country, and will make a point to see them all again when I retire.

If I had to guess how much the engine was moving, i'd say 16.5K to 17K, probably closer to 17K. I weighed the sub(6920) and the trailer(8500) for the April articles with no passengers, and the trailer was close to empty(the weights in parenthesis) for a total of 15420#.

I usually don't use much oil (1/2 qt in 2500 miles), but this trip I used 3 quarts. I have no leaks, and I believe that is probably due to the CDR connection. I'm sure there was a higher than normal vacuum in the intake before the turbo due to the increased load, which sucked more oil vapor out of the engine. That will probably be something I look at for modification.

If you can't get TDC offset set right, you may have to move the pump.

I did find that the factory installed alternator (#1) does have a funny quirk. After it gets real hot (from a large climb), indicated RPM's will drop to 0 when you let off the accelerator. Then it flickers up to idle and down to 0, more and more to idle as everything cools down, and then eventually operates normally. Ever seen that?

[ 08-27-2005, 04:16 PM: Message edited by: GMC Hauler ]

[rjwest]

No, on your alternator problem..

Sound like you had a trouble free , enjoyable trip..

Well, I started over again this morning:

Started truck and monitored TDCO:

As follows:

ECT TDCO IPT IPTD

90Deg 0 9.3 9.5

When ECT reached 169

169Deg -2.5 9.7 4.1

Did the TDCO reset by the instructions in GM book , The keyy/Pedal thing
After reset, Key on, ENg Off

173Deg 0 10.4 4.1

Started Eng, Relearn imediatly:

173 -2.5 9.2 4.2

Did the clear/relearn many times, Tried different RPM relearns also.. Always back to -2.5

Also: I noticed if the coolant temp drops below 170 deg, relean does not occur immediatly,
waits for the 170Deg ECT ( 169 my eng ).

I did go back thropugh all the old posts,
1 post made my brain ( I wonder about this some time ) HURT big time....I have not a clue what/how
the TDCO and relearn does/is for.. Guess I don't need to. Just get the numbers to come out right.
Should have left it alone I guess.

What I don't understand is how it had a -1.1
before, Could the pump have slipped?
Or this normal wear (50K miles)

Well, Have to decide to take it to a shop, or try backing down the pump,,,, Is the nuts 13 MM ???
Looks Like I need a Distributer wrench...

Oh; The only reason I did the TDCO thing was to report to the Diesel Page on the new software package. Like my Grandpa always said:Nice guys finish last.... ****script:void(0)
Big Grin

[GMC Hauler]

You are right about the 170 degree trip point for relearn. The Autoenginutiy allows a relearn without being at 170. Therefore, i'm guessing that it is a software limitation in the Tech II and Carcode, but not in the PCM, anthough I could be wrong. Maybe the Autoenginuty forces it to relearn regardless of temperature.

Take a look at your pump. Make sure it hasn't come loose (this happened to me once). It's quite possible that chain wear could have made it move the TDC offset that much, although I don't know if that is in the right direction.

The wrenches are 15mm, 12 point. one is a "s" shape, and the other is a crescent shape. If you can't find them, contact me, and I'll mail you mine on loan. I bought the snap on wrenches, because I was in a hurry. But I believe you can find them elsewhere, like Sears.

Keep me posted.

[rjwest]

Thanks for prompt replies,.

I think i will run it a while, no hurry to fix it,
check napa for wrenches when I geet down town.
Seems like a tool that I may have a need for along with the 100lbs of spares.
still a weeks before I head out to Maine...
if I can't get it fixed, t'll go to the local Standyne guy..

I see the 2 ports on the PMD for the fast idle. but no wire color, do you have to add pins to the connector....?

Thanks again,

[GMC Hauler]

You sure do. I have a couple of pins with your name on them if you wish...

[joed]

rj,

I also have the Carcode software and noted the same thing: My TDC offset went from -1.4 to -2.5 when I did the manual TDC re-learn via the throttle pedal. It seems like it shoots toward the upper limit and sets it there. It seemed to run rougher/louder there so I broke down and went to dealer to get it timed. He was able to get to the coveted -1.94 setting (had to move the IP, though). The truck does seem to run better at that setting.

I'll have to check out the latest Carcode download, the cylinder balance would be interesting.

Joe.

[rjwest]

joed, what enhanced code did you use?

What was the procedure.

How did the service set the TDCO, did they just clear it and let the PCM do it or did they do something with the Tech2,

Was the TDCO really at -2.5 with the tech 2 ?

GMC Hauler : How do I get in touch with you, is your email changed. ? contact on your home page ?

Would like the pins for the fast idle,

Off to get gm wreench, 17 dollars, Figure I can use it for something,

Thanks for the offer of your loaners....

[GMC Hauler]

rj,

Drop me a message on the picture trail account guest book. My email has not changed, if you still have it.

[joed]

rj,

I re-read your orig. post. I didn't do the TDCO test you mention. I just used the enhanced data window for the L65 diesel option to read the data (the 110 or so parameters) before and after I foreced the re-learn.

As far as the tech., he used the Tech II - it did have the same reading of -2.5, which he thought was the upper limit before it would throw a code. He used the Tech II procedure to learn - it then went to a positive TDC so he had to move the pump and re-do the procedure until it locked on the -1.94.

Joe.

[rjwest]

OK Thanks, What I understand is, The TDCO was reading -2.5 when you did a read with the carcode,

You than did a Throttle procedure relearn and it was still -2.5.

The tech 2 confirmed that the tdco was in fact a -2.5 and the carcode was accurately reporting the parameter.

It appears the tech 2 does something differantly that a Throttle relearn does not .
IE -2.5 vs a positive TDCO. Do you agree?..

Trying to make sense out it all.

[joed]

Actually, I started with a TDCO of -1.4 with the carcode, did the throttle re-learn, and it went to -2.5. I didn't try the throttle re-learn again as I figured it would require physically moving the IP.

I'm still trying to understand it all as well - near as I can tell the Tech 2 can command the stepper motor to move the IP within a window, hitting both pos. and neg. values to lock the TDCO on?. On mine, it started out at -2.5, then locked in on a pos. TDCO. It was then outside the "window" and the pump had to be moved to get it to lock the -1.94.

The carcode doesn't seem to have the capability of moving the stepper motor, at least yet. It would be nice if he could incorporate that.

Thanks. Joe.

[rjwest]

Good stuff, Do you know which way they moved the pump? Sounds like normal wear retards timing to out of spec. And pump should be re-timed periodicaly.

Hope an EXPERT reads this and can en-lightlen us...
Thanks for prompt reply,

[JohnC]

I'm not an expert, but I play one on the internet...
;)

AFAIK:

When (a tech II) commands TDC offset learn, the PCM moves the stepper motor to the least advanced position. It then measures the angular difference between TDC referenced by the crank position sensor and pump TCD measured by the optical sensor. That is the tdc offset and the value gets stored in the PCM for future reference.

If the other software package is commanding TDC offset learn, the process should be the same as it's handled by the PCM, not the scanner.

If you read -1.4 and then learned -2.5 the pump must have been moved since the previous learn cycle. Wear in the chain would tend to retard the timing, reducing the offset rather than increasing it. Another possibility is that one of the critical components had been replaced and the value was not re-learned.

There is no need to re-time the pump to compensate for wear. Once the PCM knows how to corelate the crank position and the optical sensor, even moving the pump doesn't affect the timing. One problem that could potentially arise, however, is if the wear (or pump movement) shifted the pump out of the range the stepper motor can compensate for; then the timing would be affected, and you might even see a DTC code.

[rjwest]

Thank you john C.
Pump has about 50K miles since rebuild,
No other components changed except PMD remoted.
I notice a large differance from pump 'mark, and 'block' mark. ??? about 3/4 inch...

[Dimsdale]

GMC Hauler:

I have a question for you. I just got my AutoEnginuity scan tool, and would like to check a few things before I start monkeying with the settings.

I put a new pump in a few weeks ago. Scribed the timing cover and put the new IP in exactly the same position as the old one. Runs fine etc., but I get an Actual IP timing of 12 deg, and a TDC offset of -1.26.

First, is the 12 deg ref to BTDC, or would that be a negative number? I find it hard to believe it would run at 12 deg ATDC.

Should I set the base timing the hard way (pump turning), or can this be set via the desired IP timing setting (when I tried that, i.e. set to ON, it ran like crap with mucho smoke to amuse the wife! Reset it to OFF, and ran normally.) Figured I better check with the expert first!

I figure that once the actual timing is set to the prescribed -8.5 or so, I can set the TDC offset to -1.5 - -1.97, depending on how agressive I want to be (probably do the -1.5 first and see how I like it).

Thanks in advance for all your help. I would be happy to send you a email address if you prefer.

Dimsdale

[Aryeh Levy]

thinking about autoenginuity and carcode
Do both do the TDC offset, and read all those values?

Can you set boost level, and glow timing with either?

How difficult is it to perform the TDC offset for the l65 engine? I don't want to have to memorize commands to type to the computer, i want it point and click (i'd be okay with typing commands if i had such a list)

i had an elmscan unit, but am returning to manufacturer because i specified for diesel operation, and said dont send it unless it works for diesel - then somebody on this board said it was a known issue. so im getting a refund.

i want somthing that does everything a tech II does, but software package.

(it would be swell if i could reflash my pcm too) haha doubt anybody's got that

The throttle position affects the offset, correct? the higher the rpm, the more advanced?