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So for a few months now my MJ has been running rough once it idles for about a minute after start up. Gets worse as it heats up. I've checked everything. 02 sensor, CPS, TPS, MAP, IAT, CTS, cleaned throttle body (it's a bored out one. Clean as a whistle). I've tightened my intake bolts and plan to change my exhaust manifold and the gasket soon to rule out any possibility of a leak. I've deleted the EGR and the Jeep already had the Cat cut off (planning to redo the whole exhaust and add a cat again to regain the back pressure). I've refreshed grounds and indexed the distributor. Changed plugs/cap/wires/rotor within 5000 miles ago. Tested fuel pressure and the regulator and both check out as good. 

 

Any idea where I should start next? It's frustrating me because I want to get it running perfectly before I continue doing other work to it. 

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Did you check O2S heater circuit? Disconnect O2S. On the component side measure ohms between pins C229_A and C229_B. Should read ≈6Ω's.

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9 hours ago, Ωhm said:

Did you check O2S heater circuit? Disconnect O2S. On the component side measure ohms between pins C229_A and C229_B. Should read ≈6Ω's.

This^^.

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18 hours ago, Ωhm said:

Did you check O2S heater circuit? Disconnect O2S. On the component side measure ohms between pins C229_A and C229_B. Should read ≈6Ω's.

My pins were not labeled but I tested the red and black wires and got exactly 6 OHMs. Is this test to be done with the engine hot, or cold?

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With O2S disconnected. Measure C229_B(BLK) on the harness side for a path to ground (0 ohms).

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11 minutes ago, Knucklehead97 said:

Is this test to be done with the engine hot, or cold?

 

Measurement should be taken at room temperature. 6 ohms prove good O2S heater.

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12 minutes ago, Ωhm said:

With O2S disconnected. Measure C229_B(BLK) on the harness side for a path to ground (0 ohms).

With O2S disconnected and IGN SW in the ON position, measure C229_A(ORN) on the harness side for voltage (B+).

Do both of these test.

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When testing the black wire it came back with .002 OHMs. Testing the orange wire for voltage with the key in the on position did not show any voltage unless the black terminal of my multimeter was grounded through the grey wire (c on the plug). It only showed 5 volts though. Even grounding the black terminal of the multimeter through the frame did not show a reading on the orange wire.

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Need two (2) more voltage tests. Use the Diagnostic Connector (should have yellow covers on them). Ground DVOM at the battery terminal.
KEY ON
D2-4 & D2-9. Looking for B+ voltage.
 

D1_D2.jpg.21131592d105be7c66782d6eacba95ee.jpg

 

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4 had 11.7V and 9 showed no volts. Upon moving the relay center back to look at the wires, I found this...

 

An utter mess. There's a fat orange wire that is nasty and has breaks in the insulation across about 12 inches of it.

IMG_20190515_190502.jpg

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Yellow is the wire I was tracking. Also suspect faulty O2 Heater Relay.

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2 minutes ago, Knucklehead97 said:

I'm suspecting faulty wiring?

 

Look like no voltage to the O2S.

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11 minutes ago, Knucklehead97 said:

Which wire from the relay supply's the voltage to the heater?

 

Orange going from the O2 relay (C228_3(87A)) to the O2S.

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I found this little bundle of poorly soldered orange wires wrapped in duct tape. Any idea what they are? Also found that the relay that Google said was the heater relay, was not actually the heater relay. Instead of being the first relay on the right, mine is the second relay from the left. The one I'm pointing at. The right 2 relays have 4 terminals in use and have 1 wire with 12v power with key OFF. The left 2 relays have 5 terminals in use and only have 12v if the key is in the ON position. The heater relay has a yellow wire (86) which has 12v power to it with the key ON. but upon back probing the relay with the key ON, the orange wire (87a) does not have power still. There is also 2 orange wires coming off of 87A. Any reason why? The fat orange one has got multiple breaks in the insulation. I'm thinking by the end of this I will have to replace a good section of it. The engine does NOT have to be running to have power to 87A, correct?

IMG_20190516_125730.jpg

IMG_20190516_125048.jpg

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I also found a bundle of yellow wires that were poorly soldered and wrapped in duct tape. They were further down toward the firewall though.

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Complex loss power today. Needed new transformer. Building back to normal now. I'll check your list and get back with you one or two at a time.

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6 hours ago, Knucklehead97 said:

I found this little bundle of poorly soldered orange wires wrapped in duct tape. Any idea what they are?

IMG_20190516_125048.jpg

 

One (1) of those wires should go to the Fuel Pump Relay (C216_4(87)) or one of those wires should go to Diagnostic Connector D1_6?

1988401347_RelaysON_OFFwithPins.jpg.a1bc50e0a13692f99f147c6ff070dadb.jpg

 

 

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6 hours ago, Knucklehead97 said:

Also found that the relay that Google said was the heater relay, was not actually the heater relay. Instead of being the first relay on the right, mine is the second relay from the left. The one I'm pointing at.

 

You can slide the relay blocks back or forth to dislodge them and place them in any order you want. Makes me think somebody was doing something at one time.

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6 hours ago, Knucklehead97 said:

The heater relay has a yellow wire (86) which has 12v power to it with the key ON. but upon back probing the relay with the key ON, the orange wire (87a) does not have power still.

Pin 86 is not tied to 87a. Yellow on pin 86 should be the Fuel Pump Relay.

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6 hours ago, Knucklehead97 said:

There is also 2 orange wires coming off of 87A. Any reason why?

Not sure about this one. If it the O2 Heater Relay, could be one wire for O2S Heater, other wire for D2-9.

 

6 hours ago, Knucklehead97 said:

The engine does NOT have to be running to have power to 87A, correct?

If we're talking about the O2 Heater Relay, KEY ON works, relay needs to be installed. No need for engine to be running.

O2 Heater Relay pinout.

Pin 1 (30) Yellow

Pin 2 (85) Gray/Yellow

Pin 3 (87a) Orange

Pin 4 (87) Orange/Black

Pin 5 (86) Orange

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