93 Northstar 4.6 hodrod high idle

[BodybyFisher]

I want to talk to you off line regarding PCM flashes and editing bin files, I have been a computer nut my whole life and this interests me a lot.  I want to do some experimentation, I am an electronics student always reading, have built circuits, kits and done upgrades, repairs and modifications and have good soldering skills, but need to work on surface mount chip soldering which is tricky as you know.  I truly understand how important flux is these days!  

Let me know if you need any help, Ill wait for the photos.    You might have to restore the cooling system to OEM to get the system to function correctly.  We can help

[crackerjacc]

23 hours ago, BodybyFisher said:

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. 

 

With regards to the coolant system.  No surge (purge) tank.  The red hose in the picture is attached to a fitting in the top of the radiator essentially just attaching to the radiator.  The rest is as stock except where the green circle is there is a cut-off or diverter valve for the vintage air conditioning system.  When I find out more info on the vintage air I will see if it's a bypass style or if it stops the flow all together. 

I see two issues with this already, in the stock setup coolant flows continuously through the throttle body and heads to the surge tank than through the heater core and back.  At some point if the temperature gets high enough the thermostat opens and allows coolant in the main large rad hoses to flow through the radiator and cool off and then closes when cooled enough and stops the flow to the radiator all the while still flowing fluid through the throttle body, head, surge tank, and heater core.  Correctly me if I'm wrong but without a surge tank, the way this is setup no flow of coolant throughout the throttle body, heads etc etc is allowed to occur and will just buildup pressure since one side is hooked into the radiator with nowhere to go?  Is installing a surge tank the only solution OR can I "T" in the hose (red circle) into one of the heater hoses and create same effect? (forgetting about the possible shut-off valve issue for a moment and assuming it's free flowing like stock)  The radiator has a 15pse cap on it.

[BodybyFisher]

The top of the tank has 2 to 3 inches of space for the purge line to dump into,  i dont know if there is similar space in the radiator to allow for purge line flow.  The lack of space may stop purge flow.  You might try putting a high pressure clear hose if only a couple of inches long on the purge line to observe flow.

The green circle you show is over the heater pipes.  Ill post a better photo of the area for you

[crackerjacc]

10 hours ago, BodybyFisher said:

The top of the tank has 2 to 3 inches of space for the purge line to dump into,  i dont know if there is similar space in the radiator to allow for purge line flow.  The lack of space may stop purge flow.  You might try putting a high pressure clear hose if only a couple of inches long on the purge line to observe flow.

The green circle you show is over the heater pipes.  Ill post a better photo of the area for you

With regards to the factory setup, from reading the factory manual's section on how the cooling system operates on this motor, and the hose on the bottom of the surge tank that "T" into the heater hose, I would assume there must be constant flow of fluid in this part of the coolant circuit correct???  And the thermostat only open's to allow fluid through the radiator circuit when it detects the coolant to hot, then closes flow to the radiator when it cools down?

I understand what you mean with regards to the surge tank and a bit of space on the top acting as an expansion area so just "T"ing in the hose into the heater circuit wouldn't work correctly.  It also requires the ability to fill fluid into that side of the coolant circuit otherwise if you just fill the radiator and the thermostat is closed the heater core and surge tank circuit wouldn't get fluid properly and air pockets would occur.  Crap, has anyone used an aftermarket nicer looking type surge tank of sorts on their Northstars and similar??  I mean it's just a plastic tank but has to handle the 16+ PSI this circuit runs.  Why are the ugly plastic factory replacement tanks so expensive!!

Shifting gears so to speak - does anyone know the type and how many pulses per mile the VSS on the trans-axle produces for the ECU?  Would any VSS unit that produces the common GM 4000PPM work if this is what the ECU requires?  Since we are running a 700R4 I'll have to see if the aftermarket cruise control unit's VSS sends out a signal pulse I can use for the ECU.  The lack of VSS signal to the ECU could be the cause of the high idle issue.... I hope!  One step forward, two steps back.....

 

[crackerjacc]

21 hours ago, BodybyFisher said:

I want to talk to you off line regarding PCM flashes and editing bin files, I have been a computer nut my whole life and this interests me a lot.  I want to do some experimentation, I am an electronics student always reading, have built circuits, kits and done upgrades, repairs and modifications and have good soldering skills, but need to work on surface mount chip soldering which is tricky as you know.  I truly understand how important flux is these days!  

Let me know if you need any help, Ill wait for the photos.    You might have to restore the cooling system to OEM to get the system to function correctly.  We can help

No problem, I can try and answer any questions you have but admittedly it's been 20 years since my second round of University so I'm not always up on the latest and greatest tech these days.  In some ways it moves fast, in others I'm stunned at how slow tech is progressing.

[crackerjacc]

Does anyone know the approximate capacity of the stock expansion/surge tank??  Looking at universal billet aluminum units, any recommendations for something is good quality and looks good?

[BodybyFisher]

15 hours ago, crackerjacc said:

Does anyone know the approximate capacity of the stock expansion/surge tank??  Looking at universal billet aluminum units, any recommendations for something is good quality and looks good?

Personally, I would use the OEM unit, along with the heater pipes at the rear of the engine and loop the heater core circuit.    There is a circuit that circulates coolant.

If I had to guess the oem tank is about a gallon. 

Ill try to find a photo of the heater pipes 

[BodybyFisher]

 

[BodybyFisher]

Here are 4 pages that will help you to understand and diagnose the ISC motor circuit.  

[crackerjacc]

Thanks again.  We purchased the two big factory service manuals for this motor so I'll look up the info.  I haven't worked on the car in a week or so as I was waiting for some parts to come in to redo the coolant system, they just came in but it might be Tuesday before I can get at the car again. 

As a side note, I've been talking back and forth over email with Western's Garage and we might consider modding the ECM bin to run the car in open loop mode all the time.  Apparently this is how they run in boats and is not an issue.  Given how much this car is different from stock it maybe an option.  I'll keep you posted.

[crackerjacc]

Can anyone tell me the size of hose this is?  Heater hose to WP housing and also the line the surge tank T's into at the front.  Also what is the proper size hose that goes from the surge tank to the throttle body?

[BodybyFisher]

It is about 6 to 7 inches long, it is a formed hose with a slight angle in it.   

However, I have used a standard hose in that location with success.  I am pretty sure it is 3/4", if not it will be 5/8" and it worked fine with new clamps.  Those were the only 2 hoses I have in my supply, so one will work.

[crackerjacc]

1 hour ago, BodybyFisher said:

It is about 6 to 7 inches long, it is a formed hose with a slight angle in it.   

However, I have used a standard hose in that location with success.  I am pretty sure it is 3/4", if not it will be 5/8" and it worked fine with new clamps.  Those were the only 2 hoses I have in my supply, so one will work.

darn, i think you are right.  I didn't make it to the shop today but I grabbed a bunch of 5/8" fittings and joints for the expansion tank.  I should have look ed before. Oh well, I'm pretty sure the heater and surge main hoses are 3/4" now that I think of it.  The smaller surge hose I'm not sure though. 1/4"?  3/8"?

[BodybyFisher]

Pretty sure its 3/8" is you are talking about the purge line.......

[barczy01]

3/4

 

[crackerjacc]

Finally got the cooling system redone Friday but I won't be able to test anything til Tuesday.

 

Question, what causes these motors to momentarily hold the idle up a bit before dropping down when you rev the motor up from idle?  I know the ISC motor (plunger motor) does this but is this normal for these engines?  What I mean is if it's idling and I rev it up and let go of the accelerator it drops to around 1000rpm holds it there for maybe half a second to a second before decreasing to idle speed.  It's not cable bind or anything like that, it appears the ISC extends when the engine is rev'd and is slow to retract.  New ISC and TP sensors.  There is no vehicle speed sensor so I though perhaps this was playing a role but Westers seems to think this wouldn't cause the issue.  Any thoughts?

This is what I'm working on.  Not all dolled up with the engine covers etc but you get the idea.

[BodybyFisher]

If this is a 93, you have an ISC motor that controls the return to idle along with speeding up the idle when the pcm senses increased load like the steering pump drag while turning .  The motor or mechanism may be sluggish or slow returning to idle or it is adjusted too far out.   The plunger should not touch the linkage stop when the throttle is closed.   Does it click?, if so it might be shot, replace it. The grease also dries up inside.   Inside the unit is a closed idle contact that retracts the plunger when the throttle linking stop contacts the end of the plunger. 

Check for vacuum leaks also, that show themselves up the rpm range.   On the top of your throttle body is a sensor (I don't know its name and don't have time to look up what it is), it has 2 hoses attached to it that I have seen crack, that is unmetered air that will boost the idle, I have seen them crack very tight to the larger black hard plastic.   Inspect that closely for cracks it might be the MAP. 

Observe the ISC control, for lagging.  

What did Westers say about the idle increasing in closed loop?   Is that fixed?   When the idle increases, is it increasing because the ISC plunger pushes the throttle open? 

See this thread if you have not seen it already, I started it back in August and it includes a link to Barry who did a fantastic dissection of an ISC, it should be illustrative.

 

[BodybyFisher]

How did you treat the CAM covers?, are they powder coated or painted?, they look great.

[crackerjacc]

2 hours ago, BodybyFisher said:

If this is a 93, you have an ISC motor that controls the return to idle along with speeding up the idle when the pcm senses increased load like the steering pump drag while turning .  The motor or mechanism may be sluggish or slow returning to idle or it is adjusted too far out.   The plunger should not touch the linkage stop when the throttle is closed.   Does it click?, if so it might be shot, replace it. The grease also dries up inside.   Inside the unit is a closed idle contact that retracts the plunger when the throttle linking stop contacts the end of the plunger. 

Check for vacuum leaks also, that show themselves up the rpm range.   On the top of your throttle body is a sensor (I don't know its name and don't have time to look up what it is), it has 2 hoses attached to it that I have seen crack, that is unmetered air that will boost the idle, I have seen them crack very tight to the larger black hard plastic.   Inspect that closely for cracks it might be the MAP. 

Observe the ISC control, for lagging.

See this thread, I started it back in August and it includes a link to Barry who did a fantastic dissection of an ISC, it should be illustrative.  

I just reviewed this thread, what did westers say about the idle increasing in closed loop?   Is that fixed?   When it increases, is it increasing because the ISC plunger pushes the throttle open? 

  

 

Thanks for the info.  I'll read through it.  I'm no expert on these N* motors and with it being so different from stock it's been a challenge. 

If you have a chance could you post a pic of what the stock throttle body with proper sensors looks like?  There are a number of vacuum port blocked off other than the MAP itself that plug into the spacer behind the throttle body.

As far as the closed loop idle bump, Westers couldn't say.  Been trying to figure it out for a while.  We might consider running in open loop all the time.  It's very frustrating but I'll see how it runs tomorrow now that the coolant system is re plumed.

[crackerjacc]

9 minutes ago, BodybyFisher said:

How did you treat the CAM covers?, are they powder coated or painted?, they look great.

I can't say, he bought it this way and they appear to be solid aluminum pieces so I'm going to say aftermarket???  Or perhaps if the stock ones are aluminum someone must have gone to the trouble of polishing them out.

[BodybyFisher]

8 minutes ago, crackerjacc said:

Thanks for the info.  I'll read through it.  I'm no expert on these N* motors and with it being so different from stock it's been a challenge. 

If you have a chance could you post a pic of what the stock throttle body with proper sensors looks like?  There are a number of vacuum port blocked off other than the MAP itself that plug into the spacer behind the throttle body.

As far as the closed loop idle bump, Westers couldn't say.  Been trying to figure it out for a while.  We might consider running in open loop all the time.  It's very frustrating but I'll see how it runs tomorrow now that the coolant system is re plumed.

Ill do some scans from my manual on the intake and throttle body. 

Ok, they are probably aftermarket, from this company http://www.chrfab.com/   You might even call them, they use a Holley engine management system that might solve your problems, review their site.   

The OEM cam covers are magnesium and they don't appear to hold paint well, I don't know about powder coating them.

[BodybyFisher]

The next time you idle the engine when it goes into closed loop be watching the ISC motor to see if it extends.  

I want to know if its increasing mechanically or if somehow the ignition is being advanced or base idle increased in a closed loop parameter in a westers table

Typically, the idle slows and settles down in CLOSED loop, so something is not right.

[crackerjacc]

1 minute ago, BodybyFisher said:

The next time you idle the engine when it goes into closed loop be watching the ISC motor to see if it extends.  

I want to know if its increasing mechanically or if somehow the ignition is being advanced or base idle increased in a closed loop parameter in a westers table

Typically, the idle slows and settles down in CLOSED loop, so something is not right.

I know that's what's driving me nuts.  And since I can't view the code and manipulate it like I would any other car my hands are tied.  All I can do is use this Genisys 5 scanner to view codes and watch the data streams in real time etc. but least I can do that and see what all the sensors are doing when things happen.

I'll watch the ISC when I get it running and see how it reacts when it jumps into closed loop.  I feel though the commanded idle is changing when it goe sinto closed loop even though Westers says it set for the stock values around 650~700 I believe, I might be wrong there.

[BodybyFisher]

Check out these guys also, you might find that going another route makes more sense in that you have more control

http://www.chrfab.com/

Especially look at this page

http://www.chrfab.com/Ignitions.htm

[BodybyFisher]

And look at this

http://www.chrfab.com/new_products.htm