P0300: Multiple Cylinder Misfire

[KimsJeep]

So, I went to the Yamaha dealer to get some stuff for my scooter and a couple of the salesman were looking at my TJ. When I was going to the door they started talking to me about it. In the conversation I told them about how I traded my Liberty in on it and how the Liberty had all kinds of problems. Then I said "knock on wood" the TJ hasn't had one yet! Well, I must non have said the "knock on wood" loud enough and there wasn't really any wood to knock on and of course, this morning on my way home from work the check engine light came on for the first time since I have owned it.

I hooked my code reader to it and it showed only 1 code. P0300 Multiple Cylinder Misfire. My code reader has a "code connect" it will tell you the most common fixes, starting with the "top reported fix" first. The "top" fix for this code was replace spark plugs. I actually put all new plugs and wires in it back on January 25th. (this is the nice thing about having a "build thread", one can go back and see when she did stuff, LOL) I'm thinking the plugs are probably not the problem.

My code reader has SEVERAL other reported fixes. I'm going to post pics of the screen, yah because I'm lazy. LOL

There are about 16 or so other fixes going all the way up to rebuilding the motor. Hoping it won't need that. Yikes.

I have decided I'm going to start off with cleaning the mass air flow thingy. Here is a pic of it,

I know it's not the "clean engine carbon" that they are probably talking about, but I figure it is a start.

I have a question on this next pic. What is the black box at the bottom of the pic? Would that be a possible problem causing my code? Also, what is the thing the white connector on the right of the pic and what is the thing to the left of the black box?

I can tell you a couple things I have noticed since owning the Jeep as far as how it runs. It seems to run pretty good, once in a while I will get a weird rev up when I first start it, but nothing to extreme. Once when I started it to leave a restaurant it kind acted like it was "loading up". I gave it some gas when I went to go out onto the street and it was fine. Then there was the time I went on my 3 hour drive and it acted like it was missing at stops, but no code came up and in my build thread we determined that a heat shield would help fix that. I did put a heat shield on. When the check engine light came on this morning, I was making a right hand turn from one street to another and I took it a little faster then I normally do. Right after I made the turn, the engine light came on. The Jeep still ran fine and I didn't notice any missing or anything. All gauges were at normal readings.


Any other suggestions? I would like to start by doing the cheapest fixes first and see how it goes. Right now I have cleared the code and I drove to the hardware store and back and the light has not come back on. KNOCK ON WOOD Yes, I did actually knock on the wood this time. LOL

Thanks for any help you all can give.

 

[Jerry Bransford]

Exactly what brand and model spark plugs did you install January 25th?

 

[Chris]

And what did you gap them to?

 

[KimsJeep]

And what did you gap them to?

I gapped them to .040 I can't remember if I got the info from this site or another?

I just got done cleaning the throttle body. I miss named it in the post above. I didn't take the sensor off, but I did spray sensor cleaner in the two big holes that go to the big sensor.

Top before,

After,

Bottom before, yikes....

After,

In the youtube video I watch to do this, the guy reassembled everything and started his Jeep and sprayed cleaner into his air tube at the end that attaches to the air cleaner, spraying back toward the throttle body. I didn't do this, I was thinking that would just send what ever gunk in the tube, back into the clean throttle body. Should I do that???

Good news, the Jeep still starts and runs. I can't tell much of a difference just at idle. I will drive it to work tonight and see if it helped.

 

[Chris]

Which plugs did you use?

There's no need to do that. You got that thing plenty clean!

 

[KimsJeep]

Exactly what brand and model spark plugs did you install January 25th?

You know, I'm not really sure now. I tried to go look but out of the 2 that were the easiest to get too, I could only take a pic of this much of the lettering. Really didn't want to go get the tools to pull it out. I usually keep all my receipts, I went through them all and I could find the one where I went back and got the wires, but can't find the plug receipt.

EDIT: I got un lazy and went and pulled a plug. LOL This is what they are and how the one looks.

 

[Jerry Bransford]

Ok that's an appropriate conventional non-platinum plug and it would not be causing the misfires.

 

[KimsJeep]

Ok that's an appropriate conventional non-platinum plug and it would not be causing the misfires.

Thanks,

I'm going to drive it to work and back tomorrow and if the light comes back on, I think I will go buy an ignition coil pack. I don't know how old mine is, so I figure it would be worth a try. Someone on FB told me they had the same code and they replaced the plugs and still had the same code. They then did the coil and it fixed it.

I'll update tomorrow either way.

 

[Jerry Bransford]

Do you get the same misfires when the engine is cold or do they only happen once the engine has started to warm up?

 

[KimsJeep]

Do you get the same misfires when the engine is cold or do they only happen once the engine has started to warm up?

Honestly, I didn't feel any misfires on this occasion. When it kind of ran weird at the restaurant I can't say if it was a misfire or not. This is the only time the check engine light came on, and again, never felt anything wrong. I went around the corner from one street to the other and all of a sudden the check engine light came on. Oh, and it ran fine when I left work and it was about maybe 4 miles into the trip when the light came on. So it was warmed up. After checking my gauges I even gave it a little gas to see what it would do and it excelled just fine, no hiccups or anything.

The only time I can say that I think it was possibly misfiring was when I did that long 3 hour drive, but again, no check engine light and it was really noticeable that it wasn't running right on that occasion. Once I gave it gas it was fine though.

It also ran fine going to the store and back after I cleared the code. So if it wasn't for the light coming on, I wouldn't have known there was an issue. LOL

 

[RobertJ]

Misfires can be really difficult to diagnose as you're finding out OP. The only thing I can tell you is to keep at it. There are a lot of good guides out there for systematically checking the common issues from spark and fuel delivery to bad compression. The only thing you can do is go through the list.

 

[KimsJeep]

Misfires can be really difficult to diagnose as you're finding out OP. The only thing I can tell you is to keep at it. There are a lot of good guides out there for systematically checking the common issues from spark and fuel delivery to bad compression. The only thing you can do is go through the list.

Yah, that is what I am basically doing. I figure the plugs and wires are probably not the problem since they are fairly new and have been doing fine. So, I moved on to the "free" repair. I cleaned the throttle body. Today I drove it to work and back (about 40 miles total) and so far, since I cleared the code yesterday, the CEL has not came back on. Knock on wood. LOL If it does come back on, my next thing I will do is replace the coil. Then go from there till I find the problem. I figure I really don't know how old things are so if I replace them one at a time, the better the Jeep will be in the long run.

When I was out looking over things yesterday, I noticed this wire that comes from the distributer and goes into a connector, then goes into the wiring loom. This wiring it just sitting on top of the shock tower. I'm thinking that isn't where it is supposed to be laying. I did move it to where the connector was on the tower but I haven't actually tied it up. I will be doing that today. Not sure if maybe it was causing an issue or not?

I will update if the CEL comes on again.

 

[KimsJeep]

Ok, I know I was going to update this if my CEL came back on, but it hasn't and I still wanted to let you all know what it did today. I am never going to say how well the Jeep has been compared to the Liberty again. LOL

Today I drove it shopping, came home dropped the groceries off and headed to Petsmart and Home Depot. Then about 30 mins. later went to lunch with hubby. After we ate, I decided I would head over the the feed store. Got in, started it and went to take off kind fast to try to beat a car that was coming down the road. It ended up hesitating. Kind of like bogging down. I let off the gas for a split second and gave it gas again and it went fine. Drove to the feed store and back no issues, no cel.

I then drove it back to hubby's work and took care of some stuff with him and when to leave and it wouldn't start. Turned the key and lights and all came on but there was not starting. Nothing, didn't turn over or anything. I tried several times and ended up putting it in Neutral. It started right up. I'm thinking maybe the neutral safety switch may be the culprit?

Ok, on that note, I read the thread about the o2 sensor replacement and how well it did for the OP's Jeep along with a lot of others. It was also suggested with my Jeep having 196 miles, it would be a good idea to change it. I'm thinking, with today's hesitation on take off, and the previous CEL light for multiple misfire, this could be behind all of the problems lately. I will try to replace that asap.

I was telling hubby about it and he wants to replace the crankshaft sensor (I think that is what it is called?) So I may have to do that first, then do the 02 sensor. LOL you know husbands, they are always right. LOL Sorry guys. Sometimes I have a hard time convincing hubby that the people on the forum do know what they are talking about most the time. LOL

For now, I think I will just drive it. I still don't have a light on and even though it had the hesitation today, I don't feel or hear it missing. It seems to run pretty good in my opinion.