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93 Northstar 4.6 hodrod high idle


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Background:

I'm the fifth guy to work on but finally get this Northstar motor in a friend of a friends 40 Cadillac operating correctly.  It's a 93 Northstar 4.6, Ron Francis aftermarket wiring harness specific for these motors backed by a 700R4 trans.  I had "Westers Garage" send me a reprogrammed bin file to me for it which seems to work well.  I have the ability to reprogram the ECU memcal myself.

It obviously does not have the factory stock dash controls to operate the diagnostics but I do have a Genisys 5 scanning tool that appears to be able to read and diagnose this ECU and motor but i can't tell if it properly puts it the system into diagnostic mode. :( Apart from this or a true GM tech 1 or 2 unit which I don't have I haven't been able to find any supporting product to read, diagnose, or change the data streams on this motor other than from Westers but they want to sell you a complete kit with laptop etc for a lot of cash.  I would sure be nice to run TunerPro RT on this motor. :(

Questions and issues:

I'm running into the the dreaded high idle issue at startup which slowly idles itself down.  I've replaced the TPS and ISC (plunger motor/actuator) and I believe I have done the proper adjustments to set them correctly but still can't get rid of this high idle issue and the ISC actuator clicking at key turn on and off.

Question:  He has a dead man's switch that kills the battery from the entire system that he always shuts off when the car is not running.  Will removing battery power from the ECU always cause it to do a relearn at startup of the TPS and cause the ISC to click like crazy for a few seconds at key on and off as well as the high idle situation until it warms up?

I believe a couple of the vacuum nipples off the throttle body that are not used in this setup are capped off.  Would this cause issues with any other sensor?

Can someone tell me the correct procedure for:

1.  setting the throttle plates to the correct position for idle.  Some of the vacuum ports in the throttle body can easily be on the inside or outside of the throttle plates with only a little adjustment and I'm not sure which ports are suppose to be outside at idle or inside.  Does that make any sense?
2. Proper ISC idle speed control motor (idle plunger motor/actuator) setting and adjustment.
3.  What should the proper number, or range of, ISC counts in the ECU data stream be?

Thanks in advance.

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On the 91, different engine I know, but it was OBD1 and it used an ISC motor, there were specific adjustments for the TPS, ISC, initial idle / minimum air, I will do some research for you.  I have the 91 and 95 manuals both OBD1.   The problem you are going to have is that the adjustments were monitored through the DIC, which you can't do.   Westers PCM must have real time monitoring or its a closed proprietary system.  

I would be afraid to travel across country with the car as no one could diagnose or adjust the system.  

Disconnecting the battery will erase volitile memory and the system will go through a relearn on the OEM PCM, but I have always felt the system would default to "safe" parameters and an item like the idle would not be too far out of spec.  If the aftermarket PCM is losing its volitile memory I would expect that it would operate similarly. 

Does it eventually slow down when the engine warms up?  If that is the case it sounds like its ok in closed loop but you are having problems in open loop., ie, the idle parameter is too high in open loop.  

Does this happen everytime you start the engine or just after the battery is disconnected?

The other thing is the ISC motor, the clicking is not a good sign.  It could also be set improperly and its "trying" to drop the idle be is up against a stop and can't.  

There is a shortcut method to setting the ISC motor, I need to find it, but I recall the procedure involved retracting the plunger fully and then with the throttle fully closed adjust an air gap of .030 by turning the adjustment screw.

We have a bunch of members that are familiar with ISC motors that will step in.  

How much is the outlay to be able to tune this PCM, with laptop? That will give you real time data and diagnostics?   I am very interesting in your aftermarket tuning experience here.  

How did you uploading the bin file and programing the memcal with?

Thanks

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:welcomesmiley:

If the ISC motor is clicking it is either stripped or "hunting" - most likely hunting since you replaced it ( unless you replaced it with a defective one.) . As far as the parameters go I believe it was 0-255. Can you "drive' the ISC motor with your scan tool? If you can, retract it fully, it should idle between 5-600 rpm in Park or Neutral I've seen them idle lower, the main thing is that they idle.

As long as there are no vacuum leaks the vacuum should be okay. Connect a vacuum gauge or mighty-vac to a port and let us know what engine vacuum is at idle.

The PCM should have a continuous power source otherwise you will have a re-learn procedure to perform every time the power is disconnected from the PCM. If you have access to a 93 SM it will tell you which wire is the continuous power. As @BodybyFisher mentioned EEPROMs are volatile memory chips.

Can you view and change the bin file? What parameters does it show?

May not help but here is the idle learn:

TP SENSOR/IDLE LEARN PROCEDURE 
 

  1. Outside air temperature is at least 50°F so that the A/C compressor will turn "ON".
  2. Start the engine.
  3. Allow the vehicle to idle continuously until the coolant temperature is 175°F, then idle an additional 5 minutes.
  4. At end of 5 minutes, enter diagnostics (engine still running).
  5. Turn ignition to "OFF".
  6. Wait a minimum of 20 seconds.
  7. Turn ignition to "ON" (engine not running).
  8. Enter diagnostics.
  9. Turn ignition to "OFF".
  10. Wait a minimum of 20 seconds.
  11. Turn ignition to "ON" (engine not running).
  12. Enter diagnostics.
  13. Turn ignition to "OFF",
  14. Wait a minimum of 20 seconds.
  15. Start the engine.
  16. Apply the brakes and place the transaxle in "DRIVE" range.
  17. Turn the Climate Control Center (CCC) to "OFF" and allow the engine to idle for 30 seconds.
  18. Turn the CCC to "AUTO", verify A/C compressor engagement occurs. Allow the engine to idle for another 30 seconds.
  19. Place the transaxle in "PARK" range and turn ignition to "OFF".

DIAGNOSTIC NOTES 

NOTE: Make sure nothing is touching or obstructing the accelerator or brake pedals during the TP SENSOR/IDLE LEARN procedure because this will prevent the PCM from performing the learn routine.

As you can see it would have been very hard for you to do a proper TPS idle learn with your modifications.

AND, 

:nopicssmiley: CUZ I haven't seen a 40 Cadillac with a N* ---  its GOTTA be sum kinda wonderful.... And  a little scary :unsure:

 

 

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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Good day,  Thank you both for replying.  This car has been a headache for me ever since I agreed to take on the project but I do like the challenge of it.  It's been well over a year or more since I've worked on this car as the owner was getting other things on it done like interior etc but tomorrow I'll be working on it for the first time since.  I'll have to respond more to your specific questions after I've had a chance to revisit what I've done and tried but as of the moment the issues I posted still stand.  This car has seen little to no road miles at this point.

Bodybyfisher - the PCM is a stock unit for 1993 that I've removed the memcal and desoldered the eproms and replaced them with eeproms allowing me to erase and burn new bin files with my chip burner.  Westers has taken the time to reverse engeneer the hex code for this car and used it to tailor chips etc for his customers.  I'm currently using a modded PCM bin and modded trans bin that was for a stock standard trans vehicle allowing me to use the 700R4 without any issues.  The code seems sound but with the car and setup being non-stock there are bound to be teething issues to address.

It's my belief, the obvious, is that all the issues I'm seeing with high idle at start are most likely due to the ECM loosing it's memory from it's previous learn and having to do it every time the car is restarted IF the battery is disengaged.  I'll have to confirm this tomorrow.

Since there is no way I'm going to convince the owner to not keep shutting off the battery power do you have any recommendation on those little battery devices used to keep ECU memory when the battery dies?  I believe they are not as popular anymore as the newer ECUs have built in battery backup and/or retain more in nonvolatile memory unlike early motherboards and memory.

I'll go through the learn procedures and see if it holds after letting the car cool off but not shutting off the battery.  I'll keep you posted.

It's an awesome looking car with the 4.6 Northstar under the hood. ;)

 

Thanks again guys!

Edited by crackerjacc
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May I ask, why does the owner not want to leave the ECM connected?   

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1 hour ago, BodybyFisher said:

May I ask, why does the owner not want to leave the ECM connected?   

He bought it as is and the previous owner had installed the deadmans switch under the dash. The previous owner never really got the motor to run right and it was running in limp mode.   It's one of the only Hot rod cars the current owner has that has a fuel-injected motor conversion so it's partly a matter of education which I've been constantly reminding him of but sometimes falls on deaf ears.  Problem being is he has a number of staff that tend to his cars when he is not around and they tend to not listen and shut stuff like this off when he's not around.

If it hasn't been obvious already he's filthy rich and has quite the collection of cars, lol.

I think I'm going to change the dead mans switch to just cut out the starter and ignition if he's worried about theft etc but to be honest I don't ever see that happening with this car.  I think it's just the cool factor of having something like it installed and hidden where no one can find it. Anyway, I'm hoping this is all that is required to make the car start up better and not race at a high RPM until it warms up.

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That was the first year of the northstar and it was a bugger. We at the dealer had to go through the ipc and get min and max values of the throttle blade and subtract to get the value. We had to adjust the isc plunger off of that. Then, we had to do a idle relearn. 

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Try this. Get the car up to temperature. When the car is in park and idling, press on the plunger of the isc with a screwdriver until the isc bottoms out. Unplug the isc and tou need a .045 gap between the throttle blade closed and the isc arm. Screw the isc arm in or out to get that gap. Make sure the throttle bore is clean. I believe you do the idle relearn when the car is cold. You will get a pcm code p085 idle relearn until it relearns itself.  

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5 minutes ago, barczy01 said:

Try this. Get the car up to temperature. When the car is in park and idling, press on the plunger of the isc with a screwdriver until the isc bottoms out. Unplug the isc and tou need a .045 gap between the throttle blade closed and the isc arm. Screw the isc arm in or out to get that gap. Make sure the throttle bore is clean. I believe you do the idle relearn when the car is cold. You will get a pcm code p085 idle relearn until it relearns itself.  

Ok I'll give it a try when it get there this morning.  Question, when the car is at operating temp and idled down and I manually retract the ISC fully back should I manually set the throttle plate so the motor idles at a certain RPM? 500rpm?  Is there a minimum closed gap that the throttle plates are suppose to be opened up to so the vacuum port holes are either inside or outside of the bore related to the throttle plate position (i.e. on the open side of the plate or inside the bore getting vacuum)?  Make any sense?

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With the isc plunger fully retracted and not contacting the blade arm the motor should idle normally low. No other adjustments should be made besides the isc plunger. Lets get this set and move the the idle relearn. clean the throttle bore. 

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16 minutes ago, barczy01 said:

With the isc plunger fully retracted and not contacting the blade arm the motor should idle normally low. No other adjustments should be made besides the isc plunger. Lets get this set and move the the idle relearn. clean the throttle bore. 

Ok I should be there in a hour and I'll give it a shot.  So I'm I correct in thinking that every time the ECU looses battery power and the car is restarted it will try and go through a relearn?

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barczy01 is using the ISC adjustment procedure I learned a long time ago, I used .030, he is using .045.   The ISC plunger retracts when pushing in, there are contacts in the ISC that cause it to retract. 

Do you have a service manual, I have a 1994 FSM and can look to see which lead needs to be connected to constant 12 volt power if you are unaware.  

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

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Ok, according to the 94 FSM, a 10 amp fuse (B13) in the engine compartment fuse block provides constant power to the PCM at terminals 2C4 and 2D5.

Fuse A3 (10 amp) which is only powered un RUN, provides power to the PCM at terminal 2D5.

Hope that helps

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

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Hi, just getting a chance now to report back as it was a very long day.  Came in the door and got shifted to fix something on a 69 Boss Mustang, then a 53 Chevy wagon Hot Rod.  Finally later in the day had a chance to try some stuff out on the 40 Caddy.

First I got rid of the stupid battery shut-off.  Someone had bypassed part of it anyway to power the remote door poppers so it's not like he was saving battery power by using it.

I started it up and it actually didn't idle too high.  I let it warm up and tried to push the plunger back but it was not going to move so I shut off the car removed the ISC and used a 9volt battery to retract it to it's fully closed position.  I then reinstalled and used the .045 gapping.  I turn the key on then off for 20 seconds, then repeated five times.  Not sure if this make the ECU learn the TPS or not but when it started it started nicely and idles around 820ish RPM in Park.

At about 160 degs it went into closed loop and immediately jumped about 100RPM for whatever reason, 950~1000rpm in Park.  I let it run for a while and the coolant system boiled over and spat coolant allover the ground, not out of the rad cap but the overflow.  A LOT of fluid so I shut it off. :(  I heard it burping some fluid back into the block as it cooled but think there must be air in it now.  According to the scanner it was in 180~190 deg range at the time which is normal I believe.  The rad is a heavy duty four core aluminum unit.  Is there any known issues that cause over heating like this?

I'm going to take some readings with a infrared meter tomorrow and see if the scanner and infrared readings of the block and at the rad are similar or way off.

As for the RPM change when it goes into closed loop, I'm going to check with Westers and see if the commanded idle RPM in the code is different for Open loop and Closed loop for whatever reason and go from there.  I hope to get this resolved soon as the owner is getting really frustrated with this car.

 

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Obviously check for a bad cap that is not sealing or letting loose at 7 pounds

Check the coolant for combustion by products, by using a BalKamp block tester from NAPA.   A head gasket breach superheats the coolant and you get false boiling. 

Make sure that the purge line is clear, its the line that runs from the engine to the top of the tank it lets AIR out of the system.  Pull the hose, direct it into a can and idle the engine, the coolant should flow steadily.  If not, the air purge line is clogged and the air cant get out, and the water pump cavitates.

You brought up and interesting problem, you said you pushed the plunger in and it didn't react by retracting.  That is not good.   Try that again, push the plunger in, and see if the plunger retracts.  It must.

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7 minutes ago, BodybyFisher said:

Obviously check for a bad cap that is not sealing or letting loose at 7 pounds

Check the coolant for combustion by products, by using a BalKamp block tester from NAPA.   A head gasket breach superheats the coolant and you get false boiling. 

Make sure that the purge line is clear, its the line that runs from the engine to the top of the tank it lets AIR out of the system.  Pull the hose, direct it into a can and idle the engine, the coolant should flow steadily.  If not, the air purge line is clogged and the air cant get out, and the water pump cavitates.

You brought up and interesting problem, you said you pushed the plunger in and it didn't react by retracting.  That is not good.   Try that again, push the plunger in, and see if the plunger retracts.  It must.

Ok interesting, "Purge line"???  Do you have any pictures of and where it comes from on the motor and where it goes to exactly?  Could someone have blocked this off and not installed a line?

When I say I couldn't retract the plunger I mean I put a lot of force and it wasn't going to move back no matter what.  I'll try again now that I've reset it but I get the feeling that I'll have the same result.

Anyway, I really appreciate all the help here.  I'm off to bed as I have another early morning working on this, hopefully with more success.  I'll check back in the morning.  Thanks again.

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You can't miss it.  On the top of the coolant tank is a hose that goes to the engine.   It will be the only hose other than the overflow hose from the cap.

By the way, I am not happy to hear about the radiator, the radiator is NOT GROUNDED in the OEM installation, your radiator may be creating a ground and potentially creating galvanic corrosion.  We will talk about that another time

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2 minutes ago, crackerjacc said:

I forgot to ask, what is the proper poundage of rad cap for this motor??

I believe its 16 psi.

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It is very possible that they blocked it off and that is not good.  The top of the engine is where the AIR is let out, its an automatic system in this engine, coolant and air is circulated over to the tank.  Is there a tank with this after market radiator? 

That purge line goes to the throttle body area and attaches to the crossover.  When you pull the hose off, you will notice it looks like a "BOLT WITH A HOLE IN IT", that hole must be CLEAR to allow the AIR OUT.     DONT blow in, take the bolt out and clean out the orfice or hole.   But that MUST be connected to the TANK.  It is possible with the Aluminum radiator that they eliminated the tank and heater circuits.   Take some photos if you would.

Find a 'known good' ISC.   Its possible that with all of the customizing that you don't have the correct voltages at the ISC connector, to retract the plunger.  Ill check the manual for voltages so you can check, there are 4 wires at the ISC if I recall.   Pushing the plunger in, causes two contacts to make contact causing the ISC motor to retract the plunger.    It works when you take your foot off the gas pedal, the linkage hits the plunger, the contacts touch, and the motor retracts the plunger, to slowly lower the RPMs.   it does not sound like the retraction feature is working.  

Do you have a factory service manual?

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See the RED dot, that is at the coolant tank, the hose runs across the engine to the throttle body heater circuit, then out of that to the bolt with a hole in it, if I recall. 

NSCoolingSystemCircuit.JPG

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I beginning to think the previous owner didn't do his homework and left out a few things on the coolant system.  I'll take some pictures when I get to the shop this morning.

I sent Westers the last bin files for a check over with regards to idle etc.  I hope he finds something obvious that will might fix the idle issue.

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