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UPDATE: I just tested it, and I've got 14.7 volts from the alternator charging stud and battery positive cable, and 5.0 volts at the throttle body (Both TPS sensors).
What now? I was thinking of running a 5 volt jumper wire to the signal lines, to see if it forces maximum line pressure. Does that sound like a reasonable test? Because at this point, I think we're looking at bad TPS territory.
In theory I think that should work as a good test.
hook a volt meter up or ohm meter with power off and slowly roll the throttle open, it should be a linear/smooth transition. if it's jumping around or has a dead spot (OL) then probably a good idea to replace.
it does seem the voltage is on the low side when @ WOT,but if the datalog is showing 100% throttle, then it should be OK.
I was thinking of running a 5 volt jumper wire to the signal lines, to see if it forces maximum line pressure. Does that sound like a reasonable test? Because at this point, I think we're looking at bad TPS territory.
Hey guys, just so you know, this didn't work; pressure stayed the same (65 psi idle), and it made the engine run like crap. Whole bunch of throttle codes.
I guess I'll see if I can borrow a known good throttle body for further testing, unless anyone has any other ideas.
One last thing: I used the early style of EPC solenoid on this build; I didn't notice until it was too late to return. I don't think this would present too much of a problem, especially since Maroon had this to say:
Originally Posted by MaroonMonsterLS1
There were year to year changes on the EPC (so the epc and internal harness will be different) but from the perspective of the external connector, they are the same.
You will find some literature that says the control table for EPC is different between the early and late epc...that's technically true...but you'll also find differences from one calibration OS to another. So...I've found no functional issue whatsoever over the years of interchanging between early and late epc.
Hey guys, just so you know, this didn't work; pressure stayed the same (65 psi idle), and it made the engine run like crap. Whole bunch of throttle codes.
I guess I'll see if I can borrow a known good throttle body for further testing, unless anyone has any other ideas.
One last thing: I used the early style of EPC solenoid on this build; I didn't notice until it was too late to return. I don't think this would present too much of a problem, especially since Maroon had this to say:
I just thought it would be worth mentioning.
Should make no difference I have swapped them back and forth for years with no notable change on function or operation. Personally I think its a bad PCS and that is what I would swap first for instance if this had happened on the dyno,
We know your max line is great unplugged so pumps good, and you get some variance with throttle.I suppose you could have a serious AFL valve issue but not high on my likely list.
__________________ Frank formerly of Performabuilt, Now just me, What can I build for you today? Call or message me. Click sig pic for my facebook
Last edited by FranksCustomTrans; 02-09-2024 at 09:21 PM.
dixie, did you put a new internal harness in or reuse?
I reused it, but it ohmed out well.
I'm planning to get the exhaust hooked up Saturday, the after that, I plan to take it by a buddy's house, who has a proper scanner, so I can command the solenoid to varying degrees.
Alright guys, after extensive testing, I'm going to switch out the EPC solenoid.
I tried testing the solenoid with two different scanners (a Bosch and an OTC), and neither of them could "step" the amperage to the solenoid; they could either turn it on or off.
A road test showed that amperage to the EPC solenoid never dropped below half an amp.
I'm sorry it's not the best picture, but that's how it looked on the scanner after a full-throttle pull on a country road.
I got the later model style that matches this PCM (Rostra, for the record.). I'm going to swap the harness, as well.
Looks like a good build plan to me. I would not lose any sleep over that reverse input drum. Be sure to sand around the drum not up and down, I'm sure you knew that though.
In my experiance it makes no difference whatsoever.
The scruffing of the drum in theory makes for a less agressive surface and can allow oil to be present under the band which is a good thing for cooling., I have done both ways as far as drivability no difference, But hope does help with cooling. Its a here nor there to me as along as the drum is flat across iS really what matters IMO.
__________________ Frank formerly of Performabuilt, Now just me, What can I build for you today? Call or message me. Click sig pic for my facebook
Here's an update: I ohmed out the '04 harness, and it's good, so I'm going to use it.
When I pulled the pan, I thought there were more metal shavings present on the magnets than there should be for about 100 miles of use. The "fuzz" on the magnets couldn't really be felt; IE: no sharp particles.
Would any of you smart guys be worried about this?
Here's an update: I ohmed out the '04 harness, and it's good, so I'm going to use it.
When I pulled the pan, I thought there were more metal shavings present on the magnets than there should be for about 100 miles of use. The "fuzz" on the magnets couldn't really be felt; IE: no sharp particles.
Would any of you smart guys be worried about this?
You ohmed it? Technically it's called "checking the resistance". Just saying.
Here's an update: I ohmed out the '04 harness, and it's good, so I'm going to use it.
When I pulled the pan, I thought there were more metal shavings present on the magnets than there should be for about 100 miles of use. The "fuzz" on the magnets couldn't really be felt; IE: no sharp particles.
Would any of you smart guys be worried about this?
I would probably not be too worried first change .No matter how clean you are some places you just are not gonna get to on the planets and drums and who know what little of something might have been in the cooler or the lines that just didnt come out . Now that is about the limit of what would be ok seeing on a first change . But for the right now I would continue on the path you are on solving the issue at hand, Either way it will have to be solved. As they say "Dont chase to many tails at once" lol.
Now if on the next change you find that or more and its short term I might be concerned.
"Signed Not one of the smart guys"
__________________ Frank formerly of Performabuilt, Now just me, What can I build for you today? Call or message me. Click sig pic for my facebook
The commanded line pressure from the ecm has everything to do with the torque model and pedal position change rate. If your mas airflow sensor is faulty, this will throw the model out of spec. If your ecm is not calibrated correctly after a swap or performance enhancement, it will throw off the model. Anything do do with the ecm calibration can throw the model off. If your model at wot is only reporting 200ftlbs or less, then it very well could be that far down on the commanded line pressure. 150 max psi could be the result of this calculation. This could be corrected in your tune potentially. Data logging of engine out put torque would shed some light here.
Hey guys, I'm back! And I still have the same problem! (Low commanded line pressure. ) The most I'm getting under load is 150 psi, although every now and then, there will be a hiccup and it will jump to 200 for less than a second.
I changed the MAF sensor, and it didn't seem to make any difference at all.
I borrowed one of the scanners from work (SHH! Don't tell anyone!), and did some full-throttle pulls at highway speeds today (60-80 mph).
Calculated engine load seems to max out at 70-80 percent, although occasionally it WILL jump to 100% for a couple of seconds.
Even when load goes to 100%, psi stays at about 150.
Here's one shot where I got it to 100%.
Originally Posted by reubone
The commanded line pressure from the ecm has everything to do with the torque model and pedal position change rate. If your mas airflow sensor is faulty, this will throw the model out of spec. If your ecm is not calibrated correctly after a swap or performance enhancement, it will throw off the model. Anything do do with the ecm calibration can throw the model off. If your model at wot is only reporting 200ftlbs or less, then it very well could be that far down on the commanded line pressure. 150 max psi could be the result of this calculation. This could be corrected in your tune potentially. Data logging of engine out put torque would shed some light here.
Here's a shot showing (after the fact) that calculated engine torque go up to 378 lb/ft (I don't think the stock 4.8 is making that much, but whatever).
I appreciate any input, because I'm running out of ideas, and please let me know if there are any other parameters that I should monitor.
Just for the hell of it, I disconnected the MAF sensor, to force the PCM into speed-density mode; it did no good. Still 150 PSI at full throttle on the highway.
I don't get it; I did everything I was supposed to on this transmission, and I can't get it running right because the engine doesn't think it's being worked hard enough.
Also, shouldn't 80% engine load equal 184 PSI (with 230 max PSI)?
Last edited by dixiebandit69; 05-24-2024 at 06:42 PM.
The PCM doesn't know what PSI the transmission is running at or that you've modified it to make more PSI. it is a dumb system or open loop. it just tells the EPC to run at a certain duty, 20%, 50%, 100%, etc. yours happens to be 230psi @ 100%. it seems to me that yours is only being commanded to a certain duty, in this case correlates to 150 psi. i am thinking something up with the tune or pcm.
this is simplified, but a lot of calibrations at say 60% load it will command the transmission to 100% epc duty (full psi). engine load to epc duty isn't necessarily a linear relationship.
The PCM doesn't know what PSI the transmission is running at or that you've modified it to make more PSI. it is a dumb system or open loop. it just tells the EPC to run at a certain duty, 20%, 50%, 100%, etc. yours happens to be 230psi @ 100%. it seems to me that yours is only being commanded to a certain duty, in this case correlates to 150 psi. i am thinking something up with the tune or pcm.
this is simplified, but a lot of calibrations at say 60% load it will command the transmission to 100% epc duty (full psi). engine load to epc duty isn't necessarily a linear relationship.
Update: I did another road test to view duty cycle, and the lowest it got was 35% (I'm assuming that zero percent is max line pressure).
01-01-2024, 05:23 PM
