YJ start / run issue

[snagista]

First time on this page so apologies if I don't do this right, I work on Cherokees and comanches mainly but took up helping my grandfather on this one.
1995 yj 2.5 manual
First symptom, randomly stalled, crank no spark, grandpa fired the parts cannon and replaced distributor (and connecting parts) cps and camps, coil, computer was sent away and tested.
By grounding the sensor ground wire to the battery I was able to get it to run but any throttle input stalls the engine
Second symptoms, stalling as mentioned, engine codes for every sensor over/under voltage and battery overcharge, battery shows proper voltage and is not overcharging, sensors show correct voltage and test fine except the TPS showing a jumpy sweep mid way through.
So my question lies, after three weeks of chasing harness and testing wires, where should I go next? I feel as though replacing the TPS is not the solution to all problems mentioned.
Appreciate any input, thanks.

 

[Chris]

First time on this page so apologies if I don't do this right, I work on Cherokees and comanches mainly but took up helping my grandfather on this one.
1995 yj 2.5 manual
First symptom, randomly stalled, crank no spark, grandpa fired the parts cannon and replaced distributor (and connecting parts) cps and camps, coil, computer was sent away and tested.
By grounding the sensor ground wire to the battery I was able to get it to run but any throttle input stalls the engine
Second symptoms, stalling as mentioned, engine codes for every sensor over/under voltage and battery overcharge, battery shows proper voltage and is not overcharging, sensors show correct voltage and test fine except the TPS showing a jumpy sweep mid way through.
So my question lies, after three weeks of chasing harness and testing wires, where should I go next? I feel as though replacing the TPS is not the solution to all problems mentioned.
Appreciate any input, thanks.

Welcome to the forum!

Since you’re getting multiple sensor codes and the TPS is showing inconsistent readings, it might be worth focusing on the wiring and connectors next. Here are a few steps you could consider:

1. **Check Ground Connections**: A poor ground can cause erratic sensor readings. Make sure all ground points, especially those related to the engine and ECU, are clean and secure.

2. **Wiring Harness Inspection**: Look for any signs of wear or damage to the wiring harness, especially where it may be exposed to heat or movement. If there are any frayed wires or loose connections, it could lead to the symptoms you’re experiencing.

3. **Inspect the TPS Connector**: A faulty connector can cause signal issues even if the TPS itself is fine. Make sure the connector is clean, secure, and free of corrosion.

4. **Check for Shorts or Opens**: Use a multimeter to check for shorts or open circuits in the wiring that connects the sensors. Sometimes, a broken wire or a short to ground can cause multiple sensors to trigger faults.

5. **Grounding Points for Sensors**: Ensure the sensors themselves are properly grounded to the engine/chassis. Sometimes, inconsistencies arise from poor grounding.

If replacing the TPS, I would recommend doing a thorough check around it as well, especially the electrical side, before jumping to replacing components. It could be that a new TPS might solve one issue but won’t address the root cause of the others.

Let us know how it goes, and good luck with your troubleshooting!

 

[snagista]

Welcome to the forum!

Since you’re getting multiple sensor codes and the TPS is showing inconsistent readings, it might be worth focusing on the wiring and connectors next. Here are a few steps you could consider:

1. **Check Ground Connections**: A poor ground can cause erratic sensor readings. Make sure all ground points, especially those related to the engine and ECU, are clean and secure.

2. **Wiring Harness Inspection**: Look for any signs of wear or damage to the wiring harness, especially where it may be exposed to heat or movement. If there are any frayed wires or loose connections, it could lead to the symptoms you’re experiencing.

3. **Inspect the TPS Connector**: A faulty connector can cause signal issues even if the TPS itself is fine. Make sure the connector is clean, secure, and free of corrosion.

4. **Check for Shorts or Opens**: Use a multimeter to check for shorts or open circuits in the wiring that connects the sensors. Sometimes, a broken wire or a short to ground can cause multiple sensors to trigger faults.

5. **Grounding Points for Sensors**: Ensure the sensors themselves are properly grounded to the engine/chassis. Sometimes, inconsistencies arise from poor grounding.

If replacing the TPS, I would recommend doing a thorough check around it as well, especially the electrical side, before jumping to replacing components. It could be that a new TPS might solve one issue but won’t address the root cause of the others.

Let us know how it goes, and good luck with your troubleshooting!

So the entire engine harness has been disconnected and looked over, that's how I found the broken sensor ground wire and spliced it out, all grounds in the engine bay have been cleaned ( dipstick tube, firewall near harness and firewall to block)
Continuity and voltage tests done on harness and sensors to check communication between computer and individual sensors

The only place I haven't chased the harness is where it goes through a connector mid way down the firewall and spliced into the main harness.

My Hanes manual for Cherokees has a few discrepancies for yj wires but I didn't think one of them would cause it.

Worse case I replace the sensor this week and see if maybe the codes drop, ie the TPS is shorting/ back feeding somehiw

 

[Chris]

The only place I haven't chased the harness is where it goes through a connector mid way down the firewall and spliced into the main harness.

I know this sounds nuts, but I had a 1999 XJ a decade or so ago that the HVAC would not work. I tried everything you could think of and replaced every single part you could. Even then, nothing worked.

After months of troubleshooting I finally decided to dig into the wiring harness. After weeks of going through the wiring harness I discovered that where the wiring harness went through the firewall into the drivers side footwell and then plugs into the fusebox, there was a break in one of the wires right there by the fuse box.

Not saying this is your issue, but this really threw me for a curveball. I spent months having this issue drive me crazy.