P0300 issue

jcslax17

jcslax17

Member
08 jku cel codes come up for catalytic converter efficiency on the passenger side as well as random multiple misfire and a crankshaft position sensor code. Replaced the cats, camshaft sensor, all 4 o2 sensors, and the crankshaft position sensor. Everything was original and had 190xxx miles on them, the crankshaft sensor was cracked. Cleared the codes and it ran great for about 50 miles, parked overnight and the p0300 code came back, but not at idle, only when the throttle is open. The motor was replaced about 12,000 miles ago along with new plugs and wires, but the coil pack is original. Should I look at the map sensor? What am I missing? I just drove the jeep from Pittsburgh to Phoenix with no issues and since it’s been in az it’s been giving me nothing but issues


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WJCO

WJCO

Meme King
I've seen some weird P0300 symptoms if you get bad gas. Not sure if that's the case with yours, but may not hurt to run a good fuel cleaner through the system.
 
jcslax17

jcslax17

Member
WJCO said:
I've seen some weird P0300 symptoms if you get bad gas. Not sure if that's the case with yours, but may not hurt to run a good fuel cleaner through the system.
Click to expand...

I was thinking of starting there. Would you recommend removing the throttle body and cleaning it too? It’s just weird that it’s only when the throttle is open and goes away completely at idle


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WJCO

WJCO

Meme King
jcslax17 said:
I was thinking of starting there. Would you recommend removing the throttle body and cleaning it too? It’s just weird that it’s only when the throttle is open and goes away completely at idle


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Click to expand...

You can get away with cleaning it without removing it as well. It's not a bad idea just for maintenance.

But if it is indeed fuel related, you still could have a symptom present with the throttle open fully. Because as the throttle opens with engine under load, as more air goes in, the engine will need more fuel to keep the mixture accurate.
 
jcslax17

jcslax17

Member
WJCO said:
You can get away with cleaning it without removing it as well. It's not a bad idea just for maintenance.

But if it is indeed fuel related, you still could have a symptom present with the throttle open fully. Because as the throttle opens with engine under load, as more air goes in, the engine will need more fuel to keep the mixture accurate.
Click to expand...

Any recommendations on a fuel system cleaner? I wonder if I didn’t pick up bad gas somewhere along my cross country trek


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jcslax17

jcslax17

Member
So the cel went away but I stopped and filled my tank up and it’s back as soon as I pulled out of the gas station. Can a bad gas cap cause the random misfire code


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