spankrjs's Biloxi, MS '83 Scrambler

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Biloxi
State
MS
Intermittent problems are so GRRRR! Is the PCM still throwing a Code #51 Lean Condition when the engine stumbles? Did you or HESCO adjust the timing on the PCM or is it at the factory setting? I know you can subtract 6 degrees of timing in the PCM but it takes one of the factory Jeep/MOPAR diagnostic computers.

On the HESCO/Mopar PCM I understood that HESCO deleted the a/c and voltage inputs/programming so their computer would not throw CEL's. On non HESCO factory computers the missing a/c input will throw a code but not trigger the CEL, the missing voltage input will throw a low voltage code and a CEL.
No, the two times it stumbled today, no CEL, no code 51, no codes at all. The stumble was too brief, maybe 5-10 seconds. IIRC, it has to be lean for like two minutes before it trips the CEL.

When it was throwing the Code 51, it still ran good, just a slight seat of the pants performance decrease. I never kept pushing it to see if it would start to stumble/buck, don't want to damage the engine. A five minute cool down, clear the code out, it would work perfect again.

The timing is all stock, no modifications. The highest I have seen the total advance on this one is around 29 degrees. On my red Scrambler with a 4.0/Hesco MPI I have seen the total advance as high as 36 degrees, no problems/pinging, works perfectly.

I have a 94/95 Wrangler 4.0 stock PCM. I have thought about plugging it in and seeing what it would do. I am sure I could figure out the AC/charging wiring, maybe.

When I scan the Hesco PCM, a few things do pop up on the scan tool, which is interesting:

1) On the system charging, it shows what the alternator output is. Not sure if it is getting this info from the constant hot or ignition wiring, but it does know the charge rate/status.

2) On the AC stuff, IIRC, it says "undetected".

3) The battery temp always has something indicated, not sure if it changes or is a set number all the time.
 

tmancj7

Basic User
City
Denver
State
CO
Interesting that the HESCO PCM does track alternator output to avoid the low/missing voltage code. I bought one of the last HESCO kits and it did not come with a manual trans PCM, ended up running a stock 1993 Wrangler 4.0 PCM. The stock PCM throws Code 33 (A/C) and Code 41 (Alternator Low Volt). To stop the CEL for Code 41, run a wire with a resistor (1K Ohm 1/4 Watt I think, maybe 1K Ohm 1 Watt) from the battery so the PCM is reading battery voltage. There are probably several places to pick up voltage and route to the PCM, it just has to be above the low volt CEL trigger threshold whatever that is maybe 12 volt. IIRC the PCM pin for voltage is Pin 37 and the HESCO harness does not have that pin or wire so you would have to add it. Battery temp is indicated on the stock PCM too, seems like it might be air temp in the engine bay. To pass the emissions test here I have to have a working CEL and it cannot be lit or it is an automatic fail.

Plugged in the DRB to watch how the Map sensor works and ended up with three codes:

1. Code 51 - O2S stays below center
2. Code 13 - No change in MAP from start to run 14 starts
3. Code 21 - O2S stays at center
O2 Sensor.jpg
Pulled the O2 sensor and had this mess, sooty and smelled like fuel. Different symptoms so not much help on your issue. I have a non-op factory a/c system I want to fix soon so following this thread has been really helpful to read.
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Biloxi
State
MS
Interesting that the HESCO PCM does track alternator output to avoid the low/missing voltage code. I bought one of the last HESCO kits and it did not come with a manual trans PCM, ended up running a stock 1993 Wrangler 4.0 PCM. The stock PCM throws Code 33 (A/C) and Code 41 (Alternator Low Volt). To stop the CEL for Code 41, run a wire with a resistor (1K Ohm 1/4 Watt I think, maybe 1K Ohm 1 Watt) from the battery so the PCM is reading battery voltage. There are probably several places to pick up voltage and route to the PCM, it just has to be above the low volt CEL trigger threshold whatever that is maybe 12 volt. IIRC the PCM pin for voltage is Pin 37 and the HESCO harness does not have that pin or wire so you would have to add it. Battery temp is indicated on the stock PCM too, seems like it might be air temp in the engine bay. To pass the emissions test here I have to have a working CEL and it cannot be lit or it is an automatic fail.

Plugged in the DRB to watch how the Map sensor works and ended up with three codes:

1. Code 51 - O2S stays below center
2. Code 13 - No change in MAP from start to run 14 starts
3. Code 21 - O2S stays at center
View attachment 74798
Pulled the O2 sensor and had this mess, sooty and smelled like fuel. Different symptoms so not much help on your issue. I have a non-op factory a/c system I want to fix soon so following this thread has been really helpful to read.

I had Hesco rebuild this motor for me, and install one of their "last" MPI kits on it. I think they went deep digging for parts to get the "kit" together.

The PCM that came with this kit has a "MOPAR Rebuilt" sticker on it. The PCM on my Red Scrambler has a "MOPAR Performance" sticker on it. Just an interesting thing I noticed the other day.

Thanks for the info on the wiring, that will come in very useful :thumbsup::cheers:

I will probably not mess with this one for a few weeks, I have to get ready to drive my Red Scrambler to Michigan next weekend :fingerscrossed:

When I get back, I will probaby check out the following:

1) Unplug the hole I drilled in the throttle plate (bypass the IAC with extra air, increases idle speed) to see how it does during extended idle/AC on conditions.
2) Check MAP sensor for proper operation (scan tool and vacuum pump)
3) Disconnect vapor canister AND power brake booster, just eliminate the possibility of vacuum leak. I don't "think" this is an issue, but I am curious why my IAC is shut at idle, is the engine sucking air from some small bypass leak somewhere? Where is your IAC at idle?
4) Change out the combination fuel filter/pressure regulator. Don't "think" this is an issue?
5) Install an in dash fuel pressure gauge. I have the gauge already, just need time to install it. It is electrical, not mechanical, don't want 60psi of fuel in the cab!!!!!!!
6) Swap in the OEM YJ 4.0 ECM, wire up the AC stuff, see what happens.

This one is still my "back up" for Michigan, if the Red Scrambler decides to crap out at the last minute. It drives fine 90% of the time, worse case, I just wont use the AC during extended idling conditions :thumbsup:

When I get back to messing with this one, I will report my findings. Glad to hear this stuff is useful, and thank you for your suggestions/experiences:thumbsup::wave:
 

tmancj7

Basic User
City
Denver
State
CO
Heck yes this stuff is useful, thank you for posting it up!

I think IAC on the DRB II is the AIS (Automatic Idle Speed) readout, if I am wrong let me know and I can go back and look at the other values. AIS at idle fluctuates from a minimum of 10 Steps to a Max of 16 Steps on this one. Not sure if altitude makes a difference in the number of steps, if so keep in mind this CJ is at 5280 feet.

Minimum at warm idle:
AIS Minimum.jpg
Max at warm idle:
AIS Max.jpg
The coolant temp on this one hangs at 181° when it is idling in my garage, which of course sent me down a rabbit hole this weekend because the CTS looks like this:
CTS Tight Squeeze.jpg
No way to change the CTS without taking off the thermostat housing so might as well change the thermostat, then the upper and lower heater hoses of unknown origin aaaaand finally fix that leaky valve cover gasket while it is apart. Everyone on here knows the drill. After all that the temp still hangs below the thermostat setting at 195°. Have fun in Michigan, Trevor
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Biloxi
State
MS
Heck yes this stuff is useful, thank you for posting it up!

I think IAC on the DRB II is the AIS (Automatic Idle Speed) readout, if I am wrong let me know and I can go back and look at the other values. AIS at idle fluctuates from a minimum of 10 Steps to a Max of 16 Steps on this one. Not sure if altitude makes a difference in the number of steps, if so keep in mind this CJ is at 5280 feet.

Minimum at warm idle:
View attachment 74831
Max at warm idle:
View attachment 74832
The coolant temp on this one hangs at 181° when it is idling in my garage, which of course sent me down a rabbit hole this weekend because the CTS looks like this:
View attachment 74837
No way to change the CTS without taking off the thermostat housing so might as well change the thermostat, then the upper and lower heater hoses of unknown origin aaaaand finally fix that leaky valve cover gasket while it is apart. Everyone on here knows the drill. After all that the temp still hangs below the thermostat setting at 195°. Have fun in Michigan, Trevor

Glad it is helpful :thumbsup:

Yes, "AIS" is the same as the "IAC" steps. I am very jealous of your DRB II :drool: I am using an "EZ-Lync" scanner, works well, but does not have all of the functionality of the DRB II. But, I can use it to scan GM, Ford, OBD1 and OBD 2. Comes in handy on GM engines, or Howell fuel injection. I might have to look into obtaining a DRB II :thumbsup:

Yep, your CTS is in a tough spot, know all about the "rabbit holes" :thumbsup::cheers::wave:
 
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