Hi all, I’ve had my TJ about a month now and this forum has been a great help to me so far. Thanks for everyone who contributes good solid content here!
So my TJ has about 104k miles on it. It ran OK when I got it, but it was a little rough feeling/vibration wise. Especially at idle and low RPM, it was the worst when driving and you had to stop at a light with it in gear. Didn’t seem to matter if it was hot or cold. ANother thing it would do, only when hot, was the idle would surge up and down between 800-1200 rpm.
A few days after we got it and had taken it on a few rides, got the flashing CEL on the dash and it was p0301 cylinder 1 misfire. That night, I found your forum and started researching next steps, so everything below was with the guidance of this community!
Round One
-Techron concentrated fuel system cleaner with 10 gallons mid grade 89 octone fuel from a good source (two rounds)
-One full can of CRC throttle body cleaner in bursts as per the instructions (to clean TB itself)
-One full can of CRC throttle body cleaner in bursts at idle through the IACV inlet port as instructed on this forum, until the bursts of CRC did not bog down the engine.
-Cleared CEL codes, did not reset PCM
RESULTS: Almost fully solved the idle surging up and down, restored some power, smoothed out idle considerably.
HOWEVER: Still get very rough idle and sometime 0301 misfire when driving and stopped, seems worse when cold now, but will also do it when warm. Idle surge sometimes comes back when I park it when hot, but it is not as severe.
Round Two
-Autolite XP985 plugs properly gapped and torqued
-Standard Motor UF296 Blue Streak coil rail
-Cleared CEL codes and reset PCM
NOTES: Plug #1 was fuel fouled and had nearly no gap. Other plugs had gaps all over the place. Inspected wiring/connections for coil, was in good shape and the clip even worked well, was not brittle. Inspected wiring for all injectors, and used a listening rod to check for good "click" out of all injectors when running.
RESULTS: Overall ran a lot better, smell of fuel in garage got a lot less prominent, lots more power and greatly improved fuel economy.
HOWEVER: Did not change any of the main symptoms, but they happen less frequently. Still get very rough idle and sometime 0301 misfire when driving and stopped, seems worse when cold, but will also do it when warm. Idle surge sometimes comes back when I park it when hot, but it is not as severe.
Round Three
-Using scanner, did an actuating test on the IACV and it responded smoothly to each setting, no sticking or bogging the engine.
-Smoke tested evap system - no leaks (no codes here but though might as well)
-Actuated purge valve closed with my scanner, verified no vacuum on intake side from canister
-Smoke tested intake/vacuum system. I was injecting smoke from the inlet tube in the air box using a pump up air blocker that came with my smoke system. The throttle body leaked quite a bit around the throttle input shaft, but only when the butterfly was closed. Opening the butterfly allowed most of the smoke to pass through to the intake.
-So I moved my smoke tester to evap canister line that goes into the intake. I found a small leak around the elbow going from the intake to the vacuum accessory harness, so I replaced that.
-Using live data scanning, I looked at bank 1 O2 sensors. upstream fluctuates up and down while downstream decreases to a low value as expected. But the system never seemed to go into open loop mode even after running for 15 minutes.
-Another full overnight cool down, I live data scanned the coolant temp sensor, ambient temp sensor, and throttle position sensor. Temperatures on dashboard gage and in the scan tool all seem correct. Actuating the gas pedal I find the throttle position sensor data to be smooth and not have any jumps or dead spots in the response curve.
-Checked ATF fill level and color, both seem good enough to tell me the transmission isn't starving for fluid and causing my issues when stopped in gear.
-Cleared CEL codes and reset PCM
RESULTS: It has been almost a week with no 0301 misfire code sitting at a stop! But really all I did was replace a vacuum elbow, so I don't trust it...
Current situation:
When cold, it will start easy and idle fine unless I put it in gear, then the idle gets rough. If I drive it before letting it warm up, it will run really rough at a stop in gear. This is when it would sometimes throw the 0301 misfire code. This is the only situation where I ever got the code. Never when moving, never when parked.
When hot, it always starts great, but it sometimes still has rough idle at stop. No codes ever when hot, and not as rough as when cold. Also if it has been driven a while, when I park it I sometimes get a slight idle fluctuation up and down. Not as bad as I did before cleaning the IACV but it is noticeable. If I open the hood when this is happening it all smooths out.
Questions:
1) Does the air leak around the throttle input shaft need to be fixed? I am getting mixed results on that in my research, but if this is fixable it may help my cold rough idle situation...
2) What live data do I need to look at to determine closed vs open loop? I am looking at the closed loop timer and I never see it change when the system should be warm enough. Maybe I am looking at the wrong data or interpreting it wrong...
Next Steps:
I am thinking I need to pull the fuel rail to do the heat soak wrap. Because when it is hot opening the hood makes the issues I am having when hot go away. Mine has injector 3 wrap and a heat shield in that one spot on the manifold from the factory, but it is all in questionable condition. While I'm at it I will probably swap to an older fuel rail with the testing valve, do a fuel pressure test and a leak down test, check all the injectors for leaks. Definitely check wiring pulse with a NOID light since I can do that one cable/connector at a time using my scanner. Probably install new o-rings. Injectors too if these look really bad or I find any leaking.
However, I am not sure any of that will help my issues I'm having when cold...
I have not looked at the MAP or Cam Position sensors yet.
Have not looked at compression, valve springs, or head/head gasket (but my coolant and oil are both clean and levels are staying same). I want this to not be my problem really really badly...
Haven not looked at intake/exhaust gasket. I do not hear any exhaust leak. I do hear a loud hiss on that side of the engine when running but I think it is coming from the throttle input shaft on the throttle body. Maybe I'll do a smoke test in the engine bay and see if anything sucks the smoke in...
I think I have ruled out coolant temp sensor, TPS, O2 sensors, IACV, and evap purge valve based on my diagnostics but maybe not?
Any thoughts on where I should go next? Thanks!
So my TJ has about 104k miles on it. It ran OK when I got it, but it was a little rough feeling/vibration wise. Especially at idle and low RPM, it was the worst when driving and you had to stop at a light with it in gear. Didn’t seem to matter if it was hot or cold. ANother thing it would do, only when hot, was the idle would surge up and down between 800-1200 rpm.
A few days after we got it and had taken it on a few rides, got the flashing CEL on the dash and it was p0301 cylinder 1 misfire. That night, I found your forum and started researching next steps, so everything below was with the guidance of this community!
Round One
-Techron concentrated fuel system cleaner with 10 gallons mid grade 89 octone fuel from a good source (two rounds)
-One full can of CRC throttle body cleaner in bursts as per the instructions (to clean TB itself)
-One full can of CRC throttle body cleaner in bursts at idle through the IACV inlet port as instructed on this forum, until the bursts of CRC did not bog down the engine.
-Cleared CEL codes, did not reset PCM
RESULTS: Almost fully solved the idle surging up and down, restored some power, smoothed out idle considerably.
HOWEVER: Still get very rough idle and sometime 0301 misfire when driving and stopped, seems worse when cold now, but will also do it when warm. Idle surge sometimes comes back when I park it when hot, but it is not as severe.
Round Two
-Autolite XP985 plugs properly gapped and torqued
-Standard Motor UF296 Blue Streak coil rail
-Cleared CEL codes and reset PCM
NOTES: Plug #1 was fuel fouled and had nearly no gap. Other plugs had gaps all over the place. Inspected wiring/connections for coil, was in good shape and the clip even worked well, was not brittle. Inspected wiring for all injectors, and used a listening rod to check for good "click" out of all injectors when running.
RESULTS: Overall ran a lot better, smell of fuel in garage got a lot less prominent, lots more power and greatly improved fuel economy.
HOWEVER: Did not change any of the main symptoms, but they happen less frequently. Still get very rough idle and sometime 0301 misfire when driving and stopped, seems worse when cold, but will also do it when warm. Idle surge sometimes comes back when I park it when hot, but it is not as severe.
Round Three
-Using scanner, did an actuating test on the IACV and it responded smoothly to each setting, no sticking or bogging the engine.
-Smoke tested evap system - no leaks (no codes here but though might as well)
-Actuated purge valve closed with my scanner, verified no vacuum on intake side from canister
-Smoke tested intake/vacuum system. I was injecting smoke from the inlet tube in the air box using a pump up air blocker that came with my smoke system. The throttle body leaked quite a bit around the throttle input shaft, but only when the butterfly was closed. Opening the butterfly allowed most of the smoke to pass through to the intake.
-So I moved my smoke tester to evap canister line that goes into the intake. I found a small leak around the elbow going from the intake to the vacuum accessory harness, so I replaced that.
-Using live data scanning, I looked at bank 1 O2 sensors. upstream fluctuates up and down while downstream decreases to a low value as expected. But the system never seemed to go into open loop mode even after running for 15 minutes.
-Another full overnight cool down, I live data scanned the coolant temp sensor, ambient temp sensor, and throttle position sensor. Temperatures on dashboard gage and in the scan tool all seem correct. Actuating the gas pedal I find the throttle position sensor data to be smooth and not have any jumps or dead spots in the response curve.
-Checked ATF fill level and color, both seem good enough to tell me the transmission isn't starving for fluid and causing my issues when stopped in gear.
-Cleared CEL codes and reset PCM
RESULTS: It has been almost a week with no 0301 misfire code sitting at a stop! But really all I did was replace a vacuum elbow, so I don't trust it...
Current situation:
When cold, it will start easy and idle fine unless I put it in gear, then the idle gets rough. If I drive it before letting it warm up, it will run really rough at a stop in gear. This is when it would sometimes throw the 0301 misfire code. This is the only situation where I ever got the code. Never when moving, never when parked.
When hot, it always starts great, but it sometimes still has rough idle at stop. No codes ever when hot, and not as rough as when cold. Also if it has been driven a while, when I park it I sometimes get a slight idle fluctuation up and down. Not as bad as I did before cleaning the IACV but it is noticeable. If I open the hood when this is happening it all smooths out.
Questions:
1) Does the air leak around the throttle input shaft need to be fixed? I am getting mixed results on that in my research, but if this is fixable it may help my cold rough idle situation...
2) What live data do I need to look at to determine closed vs open loop? I am looking at the closed loop timer and I never see it change when the system should be warm enough. Maybe I am looking at the wrong data or interpreting it wrong...
Next Steps:
I am thinking I need to pull the fuel rail to do the heat soak wrap. Because when it is hot opening the hood makes the issues I am having when hot go away. Mine has injector 3 wrap and a heat shield in that one spot on the manifold from the factory, but it is all in questionable condition. While I'm at it I will probably swap to an older fuel rail with the testing valve, do a fuel pressure test and a leak down test, check all the injectors for leaks. Definitely check wiring pulse with a NOID light since I can do that one cable/connector at a time using my scanner. Probably install new o-rings. Injectors too if these look really bad or I find any leaking.
However, I am not sure any of that will help my issues I'm having when cold...
I have not looked at the MAP or Cam Position sensors yet.
Have not looked at compression, valve springs, or head/head gasket (but my coolant and oil are both clean and levels are staying same). I want this to not be my problem really really badly...
Haven not looked at intake/exhaust gasket. I do not hear any exhaust leak. I do hear a loud hiss on that side of the engine when running but I think it is coming from the throttle input shaft on the throttle body. Maybe I'll do a smoke test in the engine bay and see if anything sucks the smoke in...
I think I have ruled out coolant temp sensor, TPS, O2 sensors, IACV, and evap purge valve based on my diagnostics but maybe not?
Any thoughts on where I should go next? Thanks!
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