Hey guys. I’ve browsed the forums a bunch but this is my first time posting. I have been having some issues with my 97 Jeep TJ 2.5L manual transmission the last few months and have become quite frustrated. The problem started presenting itself as a random cylinder 4 misfire. I am a newbie when it comes to working on vehicles and basically use YouTube and forums as my guide. lol No codes being thrown except the initial cylinder 4 misfire.
I replaced the existing iridium spark plugs with Champion Copper Plus plugs (read on forums that good old copper plugs were all that way needed) and it did not resolve the problem. I then changed the distributor cap, rotor, and camshaft sensor. Still no success.
I then changed all of the spark plug wires and the ignition coil without any resolution.
I confirmed that all four cylinders are getting spark.
I used a power probe and confirmed that all four injectors were getting steady pulse and constant voltage.
Instead of moving injectors around to see if that would help, I changed all four injectors and upgraded to 4 hole injectors since I was swapping them out. I also cleaned out the throttle body that afternoon.
I did the ECU/PCM reset that I learned about on these forums. (touching pos. cable to neg. terminal for 30 seconds, headlights on/off, etc.)
I have not received any more codes for misfires, or any codes at all for that matter. However, now I am getting backfires in the intake when under load. Could this be from switching to the 4 hole injectors?
I then changed the upstream O2 sensor without any improvement. (My former GM mechanic buddy talked me out of spending the money on the NGK sensor that I was looking at getting and I picked up a budget amazon sensor that he linked to me. I already regret not spending the money on the NGK sensor and may end up doing that next week to rule that out).
Also, I noticed it idling rougher than before and I pulled the new plugs. I noticed they were pretty black already, so I swapped the old iridiums back in and saw an instant improvement on my idle.
I had a known leak on my exhaust manifold gasket near the cylinder 4. I changed that out this weekend and although it sounds much nicer now and needed to be done anyway, it did not help with the intake backfires.
I performed a dry compression test and all four cylinders were between 175-180 and held compression.
I am getting pretty frustrated throwing parts at the jeep. I know that’s rarely a smart way to handle things, but I was hoping to luck out with an easy fix.
I have not replaced the TPS, IAC, or MAP yet. I purchased a fuel pressure test kit but have not yet run any tests with it. No Schrader valve on my fuel rail, so I’ll have to make that inline connection when I do it.
I know there are a bunch of intake backfire threads on the forums and I have tried to read over most of them. Most that I read through seemed to be dealing with people that had swapped to the 4.0 throttle body which I have not done.
Does anyone have any suggestions/recommendations on where I should go from here? I go tent camping weekly and my whole setup is based around my Jeep. It’s been months since I’ve been able to go and I’m having major withdrawals, so ANY advice is GREATLY appreciated.
I replaced the existing iridium spark plugs with Champion Copper Plus plugs (read on forums that good old copper plugs were all that way needed) and it did not resolve the problem. I then changed the distributor cap, rotor, and camshaft sensor. Still no success.
I then changed all of the spark plug wires and the ignition coil without any resolution.
I confirmed that all four cylinders are getting spark.
I used a power probe and confirmed that all four injectors were getting steady pulse and constant voltage.
Instead of moving injectors around to see if that would help, I changed all four injectors and upgraded to 4 hole injectors since I was swapping them out. I also cleaned out the throttle body that afternoon.
I did the ECU/PCM reset that I learned about on these forums. (touching pos. cable to neg. terminal for 30 seconds, headlights on/off, etc.)
I have not received any more codes for misfires, or any codes at all for that matter. However, now I am getting backfires in the intake when under load. Could this be from switching to the 4 hole injectors?
I then changed the upstream O2 sensor without any improvement. (My former GM mechanic buddy talked me out of spending the money on the NGK sensor that I was looking at getting and I picked up a budget amazon sensor that he linked to me. I already regret not spending the money on the NGK sensor and may end up doing that next week to rule that out).
Also, I noticed it idling rougher than before and I pulled the new plugs. I noticed they were pretty black already, so I swapped the old iridiums back in and saw an instant improvement on my idle.
I had a known leak on my exhaust manifold gasket near the cylinder 4. I changed that out this weekend and although it sounds much nicer now and needed to be done anyway, it did not help with the intake backfires.
I performed a dry compression test and all four cylinders were between 175-180 and held compression.
I am getting pretty frustrated throwing parts at the jeep. I know that’s rarely a smart way to handle things, but I was hoping to luck out with an easy fix.
I have not replaced the TPS, IAC, or MAP yet. I purchased a fuel pressure test kit but have not yet run any tests with it. No Schrader valve on my fuel rail, so I’ll have to make that inline connection when I do it.
I know there are a bunch of intake backfire threads on the forums and I have tried to read over most of them. Most that I read through seemed to be dealing with people that had swapped to the 4.0 throttle body which I have not done.
Does anyone have any suggestions/recommendations on where I should go from here? I go tent camping weekly and my whole setup is based around my Jeep. It’s been months since I’ve been able to go and I’m having major withdrawals, so ANY advice is GREATLY appreciated.
