I've officially found the most unsolvable idle issue...

[Ecomike]

CEL is certainly working because it threw a code for the TPS recently and a while ago for the Cam Position Sensor. That was with an actual OBDII scanner. When I did the jeeps odometer trick, it threw code 12 (bat. disconnect), 42 (ASD relay), and 45 (turbo??) Then it threw out 55. However, the heater circuit on both oxygen sensors read 0 v... Shouldn't it read 12 v? I did it with engine on and engine off just to make sure. I even used 2 different meters

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Yes there should 12-14 volts to the heater in the O2 sensor with the engine running. Not sure if yours has a relay or not, the Renix 87-90 has relay and no fuse, later years have bunch of stuff on one fuse including the O2 sensor heaters. You may have connector issues, or damaged wires or blown fuse... need to find the FSM wiring for your year and find the routing for that wiring. What year is this one again, I forget.

 

[W1zardofozz]

1997, I'll do physical inspections on the harnesses and stuff here in a bit. I'm about to test drive this and see how much better it runs first

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[Ecomike]

I just double checked and it threw code 35 just now, meaning open circuit or short in the cooling fan circuit. I'll check that as well. She's gradually running better though

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I can't find any Jeep codes listing a code 35 anywhwere? I did find this in a post that says you might be counting it wrong?

You don't have a code 35.

You have a code 12 1 space 2

a code 41 4 space 1

and 55 5 space 5

Code12 recently disconnected battery in last 50 starts

Code55 End of codes

Code 41: Alternator field control circuit open or shorted

 

[W1zardofozz]

Aha! Thank you sir, I'll certainly look into it. So basically we've even further narrowed it down to two things, a short in the alternator circuit, and bad wiring going to the oxygen sensors. It's nearly there! I just ran it up and down my road a little and whoa nelly is she running better. Aside from the misfire (wires) and hunting, she's basically fixed. A lot of it seemed to center around the poorly connected air system combined with the ASD circuit as well as the dirty throttle body and IAC. Definitely a lot happier. But not perfect

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[Ecomike]

Beyond the O2 sensor heater issues we just isolated, sounds like an alternator issue, PCM issue or most likely damaged wiring somewhere or bad grounds at the engine dip stick ground location. When did you last disconnect the battery? Did you ever clear the old codes? By disconnecting the battery? I assume by now the battery posts and clamps are all clean right?

Here's the full code list it just threw:
12 battery disconnect

35 cooling fan circuit open or shorted

42 An open or shorted condition detected in the auto shutdown relay circuit. An open condition detected in the ASD relay output circuit. An open or shorted condition detected in the fuel pump relay control circuit. An open circuit between PCM and fuel gauge sending unit. Circuit shorted to voltage between PCM and fuel gauge sending unit. No movement of fuel level sender detected

43 Peak primary circuit current not achieved with maximum dwell time. Misfire detected in one or more cylinders 1 thru 6. (4 and 6 cyls).

45 no idea honestly

21 Oxygen sensor detection neither rich or lean

-OR-

Oxygen sensor input voltage stayed above normal operating range.

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[W1zardofozz]

Beyond the O2 sensor heater issues we just isolated, sounds like an alternator issue, PCM issue or most likely damaged wiring somewhere or bad grounds at the engine dip stick ground location. When did you last disconnect the battery? Did you ever clear the old codes? By disconnecting the battery? I assume by now the battery posts and clamps are all clean right?

Posts and grounds are all clean and reading 12 volts all around, yes. Guess it's time to start eyeballing some stuff! Wish me luck lol

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[W1zardofozz]

Here's the beast in question while we wait


Https://imgur.com/PIWhqvq

https://imgur.com/NeLidZw


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[Ecomike]

Aha! Thank you sir, I'll certainly look into it. So basically we've even further narrowed it down to two things, a short in the alternator circuit, and bad wiring going to the oxygen sensors. It's nearly there! I just ran it up and down my road a little and whoa nelly is she running better. Aside from the misfire (wires) and hunting, she's basically fixed. A lot of it seemed to center around the poorly connected air system combined with the ASD circuit as well as the dirty throttle body and IAC. Definitely a lot happier. But not perfect

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Keep in mind the voltage regulator in 97 is no longer in the alternator it is in the PCM IIRC. If there are large random shorts in damaged wires in the harness ....I have read of one common one on the back side of the engine where the harness rubs on the block on later years, and the other is the where the O2 heater power wire shorts to the exhaust manifold, steering or front drive shaft or road hazards and the high current draw melts insulation and damages wires in the harness next to it on all jeeps that could throw many codes like you are seeing, and might damage the newer PCMs.

 

[Ecomike]

If you have an android smart phone you need to down load Torque pro for $5 and get one of these blue tooth OBD-II devices that read all sorts of real time time data and not just codes some for under $10 (better ones a are wee but more, hundreds of them on ebay)

https://www.google.com/search?q=OBD...la:en-US:official&client=firefox-a&channel=sb

They will give you live chart data on O2 signals lots of helpful diagnostic data

 

[W1zardofozz]

If you have an android smart phone you need to down load Torque pro for $5 and get one of these blue tooth OBD-II devices that read all sorts of real time time data and not just codes some for under $10 (better ones a are wee but more, hundreds of them on ebay)

https://www.google.com/search?q=OBD...la:en-US:official&client=firefox-a&channel=sb

They will give you live chart data on O2 signals lots of helpful diagnostic data

I actually used to have one!! I lost it... I have torque pro however!

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[d1sc0ver]

When the big vacuum line from brake booster to intake is removed, it makes that sound.