Rebuilt 4L60E issues. Finally fixed!
TECH Junkie
Joined: May 2012
Posts: 3,051
Likes: 716
From: Poplarville, MS
so the two main issues now are the fluctuations in RPM when at speeds of 45-60 MPH. Seems as if torque converter is slipping or something. I’m not sure if that is the case.
You can check if it is the TCC applying and releasing by lightly applying brake pedal. If RPMs stop fluctuating, there is a problem with TCC. A worn TCC bore in the valve body can cause this. A Fitzall TCC valve will fix this most of the time.
the other issue is when applying gas from start, the pressure and RPM raises, but the transmission hardly reacts until it reaches over 90PSI, at which I feel it somewhat jump into gear. As if a band or something is not being applied correctly
Low line pressure at low RPM seems to be the problem. Will need a scanner to continue diagnosing.
You can check if it is the TCC applying and releasing by lightly applying brake pedal. If RPMs stop fluctuating, there is a problem with TCC. A worn TCC bore in the valve body can cause this. A Fitzall TCC valve will fix this most of the time.
the other issue is when applying gas from start, the pressure and RPM raises, but the transmission hardly reacts until it reaches over 90PSI, at which I feel it somewhat jump into gear. As if a band or something is not being applied correctly
Low line pressure at low RPM seems to be the problem. Will need a scanner to continue diagnosing.
TECH Junkie
Joined: May 2012
Posts: 3,051
Likes: 716
From: Poplarville, MS
so the two main issues now are the fluctuations in RPM when at speeds of 45-60 MPH. Seems as if torque converter is slipping or something. I’m not sure if that is the case.
the other issue is when applying gas from start, the pressure and RPM raises, but the transmission hardly reacts until it reaches over 90PSI, at which I feel it somewhat jump into gear. As if a band or something is not being applied correctly.
the other issue is when applying gas from start, the pressure and RPM raises, but the transmission hardly reacts until it reaches over 90PSI, at which I feel it somewhat jump into gear. As if a band or something is not being applied correctly.
TECH Junkie
Joined: May 2012
Posts: 3,051
Likes: 716
From: Poplarville, MS
TECH Junkie
Joined: May 2012
Posts: 3,051
Likes: 716
From: Poplarville, MS
Yes, PR valve regulates max line pressure and EPC solenoid regulates the line pressure that is needed for engine load. Engine RPM also has a lot to do with line pressure. As you can see in the test with the trans unplugged, the higher the RPM the higher the line pressure.
Your pump and PR valve seems to be making adequate line pressure but for some reason it seems the PMC or EPC is bringing the pressures down to low at low RPMs.
Your pump and PR valve seems to be making adequate line pressure but for some reason it seems the PMC or EPC is bringing the pressures down to low at low RPMs.
Thread Starter
Staging Lane
Joined: May 2022
Posts: 98
Likes: 4
Yes, PR valve regulates max line pressure and EPC solenoid regulates the line pressure that is needed for engine load. Engine RPM also has a lot to do with line pressure. As you can see in the test with the trans unplugged, the higher the RPM the higher the line pressure.
Your pump and PR valve seems to be making adequate line pressure but for some reason it seems the PMC or EPC is bringing the pressures down to low at low RPMs.
Your pump and PR valve seems to be making adequate line pressure but for some reason it seems the PMC or EPC is bringing the pressures down to low at low RPMs.
TECH Junkie
Joined: May 2012
Posts: 3,051
Likes: 716
From: Poplarville, MS
I don't think that testing with an ohm meter is 100% conclusive. I may be wrong in that statement, but I would really like to see the output to the EPC change and see how that effects the line pressure. You have had 2 EPC solenoids in the trans with the same results. So, what are the odds of both having the same defect.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
Mr Bond is giving you excellent advise.
Your line pressures while unplugged are good; you can absolutely rule out a PR valve problem. The idle pressures first seemed a bit lot, but they my car idles at 900rpm, not the 600 you likely have.
I would:
1. Try another EPC solenoid. If that doesn't fix it:
2. Disconnect the MAF. This switched the ECU to "speed density" mode. Its a bit risky but just avoid WOT. If this fixes it, then your MAF is bad.
3. Last resort, turn the EPC screw to give you the pressure you need. Yeah, this is covering up some other problem, but it gives you a working car without tearing apart the trans.
Your line pressures while unplugged are good; you can absolutely rule out a PR valve problem. The idle pressures first seemed a bit lot, but they my car idles at 900rpm, not the 600 you likely have.
I would:
1. Try another EPC solenoid. If that doesn't fix it:
2. Disconnect the MAF. This switched the ECU to "speed density" mode. Its a bit risky but just avoid WOT. If this fixes it, then your MAF is bad.
3. Last resort, turn the EPC screw to give you the pressure you need. Yeah, this is covering up some other problem, but it gives you a working car without tearing apart the trans.
Thread Starter
Staging Lane
Joined: May 2022
Posts: 98
Likes: 4
Mr Bond is giving you excellent advise.
Your line pressures while unplugged are good; you can absolutely rule out a PR valve problem. The idle pressures first seemed a bit lot, but they my car idles at 900rpm, not the 600 you likely have.
I would:
1. Try another EPC solenoid. If that doesn't fix it:
2. Disconnect the MAF. This switched the ECU to "speed density" mode. Its a bit risky but just avoid WOT. If this fixes it, then your MAF is bad.
3. Last resort, turn the EPC screw to give you the pressure you need. Yeah, this is covering up some other problem, but it gives you a working car without tearing apart the trans.
Your line pressures while unplugged are good; you can absolutely rule out a PR valve problem. The idle pressures first seemed a bit lot, but they my car idles at 900rpm, not the 600 you likely have.
I would:
1. Try another EPC solenoid. If that doesn't fix it:
2. Disconnect the MAF. This switched the ECU to "speed density" mode. Its a bit risky but just avoid WOT. If this fixes it, then your MAF is bad.
3. Last resort, turn the EPC screw to give you the pressure you need. Yeah, this is covering up some other problem, but it gives you a working car without tearing apart the trans.
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
If it is normal for the engine to stall, they we will have to hope that the MAF is OK.
If it is NOT normal for the engine to stall, then we have a clue. I would make sure the MAP sensor is connected. Generally an LS engine will run as long as it has the MAF or MAP sensor. (Of course ideally both.)
While you say the problem started after the rebuild, the trans removal/install might have damaged a sensor/wiring or left something disconnected.
Granted I'm grasping for straws here, but also trying to keep the conversation going.
Thread Starter
Staging Lane
Joined: May 2022
Posts: 98
Likes: 4
I would not expect the engine to stall when disconnecting the MAF, but I have NO experience with a 1997 PCM. Perhaps someone more experienced will chime in here.
If it is normal for the engine to stall, they we will have to hope that the MAF is OK.
If it is NOT normal for the engine to stall, then we have a clue. I would make sure the MAP sensor is connected. Generally an LS engine will run as long as it has the MAF or MAP sensor. (Of course ideally both.)
While you say the problem started after the rebuild, the trans removal/install might have damaged a sensor/wiring or left something disconnected.
Granted I'm grasping for straws here, but also trying to keep the conversation going.
If it is normal for the engine to stall, they we will have to hope that the MAF is OK.
If it is NOT normal for the engine to stall, then we have a clue. I would make sure the MAP sensor is connected. Generally an LS engine will run as long as it has the MAF or MAP sensor. (Of course ideally both.)
While you say the problem started after the rebuild, the trans removal/install might have damaged a sensor/wiring or left something disconnected.
Granted I'm grasping for straws here, but also trying to keep the conversation going.
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
I know you said you checked the trans fluid level, but for future people reading this, let me review it:
The correct way to check the trans fluid level is with the engine and trans warmed up and with the engine running! The fluid should then be at the "hot" line.
You can make an approximate level check with the engine cold and off -- the level should be about 1-1/4" above the "hot" line.
(In other words, when the engine starts, the level goes down because the trans pump fills the upper parts of the transmission and the torque converter.)
If the trans pan is ever off, it is a good idea to check the accuracy of the trans dip stick - the "hot" line match the the line between the trans body and the valve body.
Thread Starter
Staging Lane
Joined: May 2022
Posts: 98
Likes: 4
Great. Yes, a scanner that shows MAF and MAP values would be useful; even better if it shows the EPC current. (Your symptom corresponds to the EPC current staying high and not changing.)
I know you said you checked the trans fluid level, but for future people reading this, let me review it:
The correct way to check the trans fluid level is with the engine and trans warmed up and with the engine running! The fluid should then be at the "hot" line.
You can make an approximate level check with the engine cold and off -- the level should be about 1-1/4" above the "hot" line.
(In other words, when the engine starts, the level goes down because the trans pump fills the upper parts of the transmission and the torque converter.)
If the trans pan is ever off, it is a good idea to check the accuracy of the trans dip stick - the "hot" line match the the line between the trans body and the valve body.
I know you said you checked the trans fluid level, but for future people reading this, let me review it:
The correct way to check the trans fluid level is with the engine and trans warmed up and with the engine running! The fluid should then be at the "hot" line.
You can make an approximate level check with the engine cold and off -- the level should be about 1-1/4" above the "hot" line.
(In other words, when the engine starts, the level goes down because the trans pump fills the upper parts of the transmission and the torque converter.)
If the trans pan is ever off, it is a good idea to check the accuracy of the trans dip stick - the "hot" line match the the line between the trans body and the valve body.
Graph of MAF and MAP at idle
MAF and MAP and 1500RPM
EPC while idle
TPS and MAP info at idle
EPC while in drive and at ~1500 RPM.
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
Nice. You did great with that scanner.
The MAF and MAP values look normal. And good that you were now able to start and drive with the MAF disconnected; that actually indicates that the MAF is good.
The EPC current changed from 1.06A to 0.18Amps. That is a bigger drop that I expected but good. We can now rule out problems with the MAF, MAP and PCM.
If the scanner is still available, the next step is to correlate the EPC (PCS) current with your trans line pressure. There should be a smooth correlation - changing from e.g. 60psi to 200 psi as the current goes from 1Amp to 0 amps.
If the pressure stays at e.g. 80 psi as the current drops and then suddenly changes to 200 psi, then likely the EPC or related valves are sticking and need attention.
Hopefully we are getting close now. I think and am hopeful that the problem is in the valve body.
The MAF and MAP values look normal. And good that you were now able to start and drive with the MAF disconnected; that actually indicates that the MAF is good.
The EPC current changed from 1.06A to 0.18Amps. That is a bigger drop that I expected but good. We can now rule out problems with the MAF, MAP and PCM.
If the scanner is still available, the next step is to correlate the EPC (PCS) current with your trans line pressure. There should be a smooth correlation - changing from e.g. 60psi to 200 psi as the current goes from 1Amp to 0 amps.
If the pressure stays at e.g. 80 psi as the current drops and then suddenly changes to 200 psi, then likely the EPC or related valves are sticking and need attention.
Hopefully we are getting close now. I think and am hopeful that the problem is in the valve body.
Thread Starter
Staging Lane
Joined: May 2022
Posts: 98
Likes: 4
Thank you for that input. I was starting to think I was getting further from an answer with those values. I will try what you asked with the stead rise of both and see what happens. After done with that, I will get the valve body back off and take all valve out to see if I can find any stick valve.
TECH Junkie
Joined: Jun 2008
Posts: 3,203
Likes: 1,391
From: Nitro Alley
Wow!
I think Bbond105 and Mrvedit deserve a round of applause for "Taken Care Of Business" while the Forum is a Ghost-Town.
I am kinda sad to see such little activity on the Forum... But we all have lives.
And it is not like I have been on the Forum recently either...
Mental Health... I am learning at a very steep gradient, is a Real Bitch!
Anyway, what Year and Model is the Vehicle being discussed?
The Unit is of a 1997 Model-Year, correct?
Is the PCM also?
These Early-PCMs were not terribly fast in terms of Processing...
Line-Rise in response to Throttle-Input was rather slow.
Including the older PCMs; this is where discussions of using a Vacuum-Modulator came from.
What is the Torque-Converter that is being used?
Depending on the STR and Stall-Speed; unwanted behavior may be exacerbated.
Cooler Circuit Temps and Pressures would be nice to have.
Hopefully this information will be more commonly monitored in the future...
(with Line-Pressure and Sump-Temp) like we monitor our Engines.
At this Point; an ATF Pressure-Gauge needs to be taped to the Windshield...
A Friend/ Passenger is needed to watch EPC and TPS data...
And lets see how things look actually during the unwanted behaviors!
Last edited by vorteciroc; Jun 4, 2022 at 01:54 AM.
Thread Starter
Staging Lane
Joined: May 2022
Posts: 98
Likes: 4
Wow!
I think Bbond105 and Mrvedit deserve a round of applause for "Taken Care Of Business" while the Forum is a Ghost-Town.
I am kinda sad to see such little activity on the Forum... But we all have lives.
And it is not like I have been on the Forum recently either...
Mental Health... I am learning at a very steep gradient, is a Real Bitch!
Anyway, what Year and Model is the Vehicle being discussed?
The Unit is of a 1997 Model-Year, correct?
Is the PCM also?
These Early-PCMs were not terribly fast in terms of Processing...
Line-Rise in response to Throttle-Input was rather slow.
Including the older PCMs; this is where discussions of using a Vacuum-Modulator came from.
What is the Torque-Converter that is being used?
Depending on the STR and Stall-Speed; unwanted behavior may be exacerbated.
Cooler Circuit Temps and Pressures would be nice to have.
Hopefully this information will be more commonly monitored in the future...
(with Line-Pressure and Sump-Temp) like we monitor our Engines.
At this Point; an ATF Pressure-Gauge needs to be taped to the Windshield...
A Friend/ Passenger is needed to watch EPC and TPS data...
And lets see how things look actually during the unwanted behaviors!
appreciate the input, you are right that they deserve that if not more for their time and help.
the vehicle is a 97 k1500 5.7 V8 with a 97 PCM. I have though about trying the popular “411” PCM swap, but a lot of trouble to go through right now. And the converter info is a bit “here say”. I do know that the builder put a high stall converter in it at first, around 2000. At which I told him was wrong and he changed it out for me free of charge. As far as I can tell now, the stall is around 1400.
as far as getting certain data, I’m not sure if it’s the scanner or something else, but a lot of data tables show as “N/A”. Like temperature. I noticed that there is a section that says “hot mode” that kicks on. It’s in one of the photos I posted. I will have to try what you said as far as trying to watch EPC/TPS data while the issues arise. Today is my last day with the scanner.