2.4 Issues

[Jigsaw]

Good morning,

My son's mother bought our son a 2003 TJ 2.4 with a manual trans last year. I was not involved with the decission (divorced) but I gladly took on the reasponsibilty of helping him fix the issues just so we can hang out and do something cool together. The 2.4 had a blown headgasket and apparently someone tried to cover it by using liquid head gasket repair to hide it. Anyways, we replaced that, flushed the cooling system, changed the timing belt and related parts, We had to replace the head and cams with a refurbished unit, etc. The Jeep fired right up and he has been driving it with no issues for three months.

Fast forward to last week. He was driving home from church and the engine just shut off. I went to where he was stranded and initially on the side of the road I couldn't find the issue. He had it towed to my house and we started to dig deaper. We scanned the PCM for codes and found p0113, p0118,p0123, p0505. The one thing these sensors have in common is a ground. Long story short I found a connector under the intake was not fully plugged in. I cleaned the male and female ends and plugged it back in. This cleared up all codes except for th P0123 which indicated a voltage issue with tthe TPS. He purchased a cheap TPS from Autozone, (I know they are not reliable but he is 16 and he purchases all parts to fix this Jeep). This cleared up the p0123 code and now the Jeep does start up. It does not run well AT ALL. It does not want to idle and it does not want to rev. You have to feather the throttle in a sweet spot. The engine is flooding I figure. Strong smell of fuel, a pop or backfire in the exhaust and when you rev it it starts to bog down immediately. I decided to purchase a Mopar TPS and it should be here soon. Do you think I am on the right track? Am I missing something?

 

[Chris]

Good morning,

My son's mother bought our son a 2003 TJ 2.4 with a manual trans last year. I was not involved with the decission (divorced) but I gladly took on the reasponsibilty of helping him fix the issues just so we can hang out and do something cool together. The 2.4 had a blown headgasket and apparently someone tried to cover it by using liquid head gasket repair to hide it. Anyways, we replaced that, flushed the cooling system, changed the timing belt and related parts, We had to replace the head and cams with a refurbished unit, etc. The Jeep fired right up and he has been driving it with no issues for three months.

Fast forward to last week. He was driving home from church and the engine just shut off. I went to where he was stranded and initially on the side of the road I couldn't find the issue. He had it towed to my house and we started to dig deaper. We scanned the PCM for codes and found p0113, p0118,p0123, p0505. The one thing these sensors have in common is a ground. Long story short I found a connector under the intake was not fully plugged in. I cleaned the male and female ends and plugged it back in. This cleared up all codes except for th P0123 which indicated a voltage issue with tthe TPS. He purchased a cheap TPS from Autozone, (I know they are not reliable but he is 16 and he purchases all parts to fix this Jeep). This cleared up the p0123 code and now the Jeep does start up. It does not run well AT ALL. It does not want to idle and it does not want to rev. You have to feather the throttle in a sweet spot. The engine is flooding I figure. Strong smell of fuel, a pop or backfire in the exhaust and when you rev it it starts to bog down immediately. I decided to purchase a Mopar TPS and it should be here soon. Do you think I am on the right track? Am I missing something?

From what you've described, it does sound like the TPS could be the primary culprit for the idling and revving issues, especially since the cheap replacement didn't solve the problem. The fact that you're already opting for a Mopar replacement is a good call.

Here are a couple of other things you might want to check in parallel with the TPS replacement:

Check for Vacuum Leaks: Given the symptoms of rough idling and bogging down when revving, it's possible there are vacuum leaks causing the engine to run lean, which could contribute to the flooding and backfiring you're experiencing. Visual inspection and spraying some starter fluid or soapy water around possible leak points might help identify any issues.

Fuel Pressure: Make sure the fuel pressure is in the proper range. An overly high fuel pressure can lead to flooding as well, so it’s worth checking if you haven’t done so already.

IAC (Idle Air Control) Valve: Sometimes the IAC can become gunky and lead to idle issues. It might be a good idea to clean or check that component too.

Coil Pack and Spark Plugs: Since you've got a strong fuel smell, make sure that the ignition system is working well. Worn spark plugs or a failing coil pack can contribute to poor combustion, leading to backfiring and the issues you're describing.

Check Engine Grounding: You mentioned a ground issue earlier; ensure that all engine grounds are intact. A poor ground connection can cause erratic behavior in multiple systems.

Hopefully, the new TPS will help stabilize the engine performance. Keep us updated on your progress, and good luck!

 

[Jigsaw]

From what you've described, it does sound like the TPS could be the primary culprit for the idling and revving issues, especially since the cheap replacement didn't solve the problem. The fact that you're already opting for a Mopar replacement is a good call.

Here are a couple of other things you might want to check in parallel with the TPS replacement:

Check for Vacuum Leaks: Given the symptoms of rough idling and bogging down when revving, it's possible there are vacuum leaks causing the engine to run lean, which could contribute to the flooding and backfiring you're experiencing. Visual inspection and spraying some starter fluid or soapy water around possible leak points might help identify any issues.

Fuel Pressure: Make sure the fuel pressure is in the proper range. An overly high fuel pressure can lead to flooding as well, so it’s worth checking if you haven’t done so already.

IAC (Idle Air Control) Valve: Sometimes the IAC can become gunky and lead to idle issues. It might be a good idea to clean or check that component too.

Coil Pack and Spark Plugs: Since you've got a strong fuel smell, make sure that the ignition system is working well. Worn spark plugs or a failing coil pack can contribute to poor combustion, leading to backfiring and the issues you're describing.

Check Engine Grounding: You mentioned a ground issue earlier; ensure that all engine grounds are intact. A poor ground connection can cause erratic behavior in multiple systems.

Hopefully, the new TPS will help stabilize the engine performance. Keep us updated on your progress, and good luck!

That gives me another round of things to check! Thank you!

I do know from what I have heard the Jeep had sat for awhile when she purchased it for him. Given the age, I would not be surprised if a rubber vaccum line is cracked and leaking. I tried to check all of them when we had it apart but since he has been driving it, anything could have happened to rubber lines now that they are getting heat cycles again.

 

[macleanflood]

ODB live data is your friend...you can do it with a $30 Bluetooth dongle and free app Torque Lite. I'd be monitoring fuel trims, vacuum and O2 voltages to start.

-Mac

 

[Jigsaw]

ODB live data is your friend...you can do it with a $30 Bluetooth dongle and free app Torque Lite. I'd be monitoring fuel trims, vacuum and O2 voltages to start.

-Mac

That sounds like a great idea. Thank you

 

[Jigsaw]

I just wanted to give an update since a lot of times these threads never get closure and I hope maybe some day it will help someone solve a similar issue. I replaced the TPS with a Mopar unit but that did not solve it. I checked all vacuum hoses, coil packs, IAC, fuel pressure, all wiring, etc. Still could not find the issue. The thing that made the most sense to me was that the PCM was possibly bad. I shipped it off to WranglerFix.com to have it tested. They sent it back the same day they recieved it and stated that it tested fine. I took them at their word and I eventually hit a dead end so I took it to a local shop to see if they could fix it. They went down the same path I did and they asked if I had the PCM tested. I told them indeed had and it tested fine. They checked a few more things and said "look we really feel it is the PCM, can we purchase one and see if that fixes it? If it is not the issue we will not charge you for the PCM" Well low and behold, that is exactly what the issue was. A bad PCM. My son has his TJ back and it runs better than ever.

 

[Cooper Smith]

I just wanted to give an update since a lot of times these threads never get closure and I hope maybe some day it will help someone solve a similar issue. I replaced the TPS with a Mopar unit but that did not solve it. I checked all vacuum hoses, coil packs, IAC, fuel pressure, all wiring, etc. Still could not find the issue. The thing that made the most sense to me was that the PCM was possibly bad. I shipped it off to WranglerFix.com to have it tested. They sent it back the same day they recieved it and stated that it tested fine. I took them at their word and I eventually hit a dead end so I took it to a local shop to see if they could fix it. They went down the same path I did and they asked if I had the PCM tested. I told them indeed had and it tested fine. They checked a few more things and said "look we really feel it is the PCM, can we purchase one and see if that fixes it? If it is not the issue we will not charge you for the PCM" Well low and behold, that is exactly what the issue was. A bad PCM. My son has his TJ back and it runs better than ever.

You still needed to replace that TPS. I had an AutoZone TPS in my '03 2.4 as well, and it died 8 months later. Lesson learned. Good that you changed it anyways.

 

[Jigsaw]

You still needed to replace that TPS. I had an AutoZone TPS in my '03 2.4 as well, and it died 8 months later. Lesson learned. Good that you changed it anyways.

I absolutley agree! It was worth it to me.