The infamous p0301. I’ve had this code on for about 3 years now, done minor things to attempt to fix it. Recently it’s getting worse. Replaced ignition coils, boot, spark plugs, fuel injectors, pcv valve, radiator. Radiator seemed to kind of give out on me. Thankfully it’s in warranty so going to swap that out soon. My code is back and with vengeance. It never left. Comes and goes with rough idling when it does come back. But today it came back with rough idling, a pissing radiator, an engine that sounds like a black hawk, and a flashing engine light. I need a fix with this asap. Please chime in, I’ve attached a link to videos and pictures. I have a 2003 jeep wrangler tj 4.0 Automatic.
Update: code p0305 just popped up, vehicle is hesitant and extremely shapely going close to 2k rpms. Have to stay below that. Radiator still spitting out some coolant from the top plastic/aluminum connect. I figure I swap the radiator for now just to clean up that leak but I don’t believe that’ll solve my problem. I changed the radiator in Jan of 23. And the p0301 code was on before that. I recently did a tune up and had the guy put on a new gasket. Could it be a gasket leak?
Another update:::
Just swapped the spark plugs to try and track the misfire. As I pulled out the plugs, a bunch of white ash came off of them. The tips were ashy as well. I remember reading something a while back about that meaning a coolant leak.
Interesting. If I do a compression test and the numbers are off, then the next step would be cracking open the head and taking a look at the valves?
Mostly head gasket...but one way or another the head needs to come out.
-Mac
-Mac
If coolant is in the oil, you may have worn bearings as well. Check the oil pressure with a test gauge.
Yep,my301 code was a tight sticky valve guide,would come and go as the valve would turn.sometimes run good for months.but never perfect.installed a rebuilt tupy head and runs like a Swiss watch now(lol)
mostat as well as its housing, new transmission fluid, oil and spark plugs. . Prior to this, I had a p0301 code that’s been on for years now and right before the car surgery p0305 popped up. But after this car surgery, new codes popped up. P0303 and p0305. No more p0301. During the process I looked at my catalytic converter. On one of the two mini cats, the honeycomb is completely gone. The other is really gunked up. Could this be the culprit? New o2 sensors too. I’m running out of money here doing the expensive stuff. Im in need of a fix. The car currently runs the same as it did right before the head gasket fix. Flashing engine light. Runs high rpm’s, can get to 60mph then starts dying. If I maintain 60mph it will start shaking and feel like the car is going to explode. So I drop to 50 and then it’s normal for a second then once again starts shaking, then I have to drop to 40 and same thing until I’m going 10mph and the car is shaking like crazy. Not overheating anymore. Any ideas.
Well if the guts of the mini cat are not there anymore,they are clogged and
in the 3rd cat,causing the engine to slow down,I left mine out(it’s only a cleanup cat)it’s not monitored.just unbolt it and shake it out or replace if you have to have it for inspections in your state.
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I did some investigating last night. I ended up finding a fuel hose that was completely cracked and half. So I went to the store. Bought a new hose and connected. It started up the truck and there was no problems. Car was running completely fine for about 30 minutes. Driving it on the road. There was only a code for a temperature sensor. I switched it out. Cleaned it. And the code disappeared. I left the battery unplugged all night. Woke up this morning. And now there’s a cylinder five misfire code p0305. They said the pushrods were bent. So I ordered new pushrods. Do you think the pushrods can be causing a misfire? There is a clicking now. As far as my cat. I don’t think this is the problem.
Update: did a cylinder clean, cylinders were fine just a little dirty but cleaned up. The cylinder head was fine no cracks and cleaned up easily. Changed all gaskets and thermostat(this was supposed to be before the previous post, but didn’t post)
Final update: the jeep is fixed. Changed the push rods, my radiator is shot thankfully it’s in warranty. Swapped it out and no coolant leaking. The hose connecting to the thermostat was also leaking. Tightened and no more leaks. The new push rods are functioning perfectly, no more clicking. And everything is properly torqued. Threw some new spark plugs because I noticed one was covered in oil. Although I don’t think that was from a leak I think it was just a messy head job. Noting, everything con be properly done by yourself. Paying other people to do this was my mistake. Engine runs smoother than ever, I’ll look into potentially getting a new cat in the future when smog time comes up in 2027 but right now she’s back baby.
Everything I’ve done to combat the misfires:
New radiator
New o2 sensors
New thermostat
New pcv valve elbow and breathers
New fuel line
New spark plugs
New coil pack
New fuel injectors
New hoses all around
New cylinder head gaskets all around
New IAT
New TPS
New push rods
Normal maintenance, oil, transmission, coolant, air filter
Everything I’ve done to combat the misfires:
New radiator
New o2 sensors
New thermostat
New pcv valve elbow and breathers
New fuel line
New spark plugs
New coil pack
New fuel injectors
New hoses all around
New cylinder head gaskets all around
New IAT
New TPS
New push rods
Normal maintenance, oil, transmission, coolant, air filter
What size push rods did you use or where did you source them? What lead to replacing them?
Constant tension clamps work great for the radiator hoses. Far superior to hose clamps. There's a resource article detailing the sizes.
Glad you're up and running!
-Mac
Constant tension clamps work great for the radiator hoses. Far superior to hose clamps. There's a resource article detailing the sizes.
Glad you're up and running!
-Mac
Melling Pushrod MPR-437 From autozone. There was a clicking coming from the head. Pulled out the rods and a few had a slight bend to them. Good to know, I’ll definitely pick some up, I’ve heard a lot about those clamps. Might as well make the switch now before I run into this issue again.
Yes,when we were younger the first thing we did was pull off the blasted squeez clamps,little did we know the screw clamps were ruining the hose end!I have had trouble getting the big one on the water pump.
Best tool for constant tension clamps:
https://www.amazon.com/gp/aw/d/B003D3N7YW?tag=wranglerorg-20
-Mac
https://www.amazon.com/gp/aw/d/B003D3N7YW?tag=wranglerorg-20
-Mac
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