I have posted before but am having a different problem now. Ok i been working on my jeep for the pass few weeks. Came accross another problem. I have put new distributor cap, rotary button, spark plug wire's, and spark plugs. My check engine light still come's on. With codes p300 and p304. Which is random misfires and misfire in 4. My jeep runs over all fine i do have a small problem when i go up little hills and sometimes at idle. It acts like it wants to die out but never does. There is also a small knocking noise when i am driving and it starts to die. I will have to give it alot of gas and it sounds like knocking or a thumping right under my feet and then it will take off and run fine. Now i havent had a chance to check to make sure fuel pressure is good yet. I dont no if i am just missing something if there could be a possible over site i am not looking at. Tomorrow i am going to check timing as well as fuel pressure. I have put a new catalytic converter on it as well as fuel filter as well as i am going to put a new muffler on. If you have had this problem or know of something else i could look at let me know. Thanks...

 

Could be alot of things. my main tests would be fuel pressure(pump/strainer) and perhaps a compression test. if you are not getting codes for O2 sensor or anything. also if your idle is getting very low maybe check the TPS or idle spped control. Just my ideas.

 

I agree that a fuel pressure test is one of the first things I test whenever I see a P0300 (random misfire). Also check for vacuum leaks. Is your idle rpm reasonable and not high?

For a 96, you should have 49 psi, plus or minus 5 psi at the fuel rail.

Good luck and let us know what you find!

 

I agree. But also are you sure the wires are on the plugs/ distributor like clicked down in place? Also I doubt this very much but maybe the new wires are arcing a crossed. Do you hear a tic tic tic sound when its running? Another thing to maybe the plugs that you put in are just bad plugs. Its rare but ive seen it a few time new plugs either have a crack in porclein from factory, or putting them in cracked the porcline. It really could be a number of things.

 

Ok the idle will be normal then when it starts acting up it drops. When it drops it will all most act like its going to die but never does. It will rev up on its own a few times then go back to a normal idle if it doesnt i have to give it alot of gas to get it to stop. If i go up a incline or if i stop then take off it happens as well. I will check the fuel pressure tomorrow to see what kind of readings i get. As far as my jeep goes once it gets over that little hickup it will run fine. I will check to see what happens with the pressure test and get back to see whats going on.

 

Also i have changed the plugs twice in the last month and checked a few time's to make sure the wire's were connected good and clicked in.

 

Take another look at the distributor and look inside the cap and on the rotor.

Inspect the contact posts inside the cap for odd looking wear marks, like heavier on some posts than others.

Check the center shaft of the distributor for side-to-side play, it is ok for the shaft to have some up and down movement, but noticeable side-to-side play is not good.

I had the random misfire problem and it turned out to be the cap.

Always good to check fuel pressure, but if that is good do back to the distributor.


QUESTION: Were you getting the Misfire Fault BEFORE you put on the new new distributor cap, rotary button, spark plug wire's, and spark plugs. -OR- Did you put them on because of the fault light/codes?

 

I was getting them before so thats why i changed them. And on the old cap i inspected it and none of the post had more wear then any other. I looked at the distributor as well and there was no problem with it either. Timing after checking today was on the mark like it should be as well.

 

I've been working the same issue on mine right now. I just put new plugs,cap,rotor, and wires. Getting p0300,p0304, took #4 plug out and noticed that the plug gap had dissappeared so I reset gap then just for laughs I pulled the #2 plug out and reinstalled that in the #4 and the other in #2. Started it back up and let it run for a while got the code again so I took the plug wire from #4 and swapped it with the #2 completely swapped on cap and plug. Started it back up just drove it home from work 35 miles no codes idled great, my question is why didn't the problem follow the plug wire from the #4 the only thing I can figure is that it just wasn't on the cap or it was jumping somehow.