P0300 Random Cylinder Misfire

[paqman]

Hey guys. Working on my in-laws 2002 Protege. It is chugging heavily at idle, nearly dying, but never actually dies. This only happens at idle. Driving at speed seems to have no issues. It also only happens after the engine is slightly warm, (1-2 minutes).

Here's what I've done so far:
CEL gives a P0300 (random cylinder misfire).
Replaced new spark plugs - no change, still chugging.
Replaced ignition coils - no change, still chugging.

At this point, I cleared the CEL, drove it around for a bit (but not long enough for the CEL to come back on). Pulled codes again, this time a "pending" code came through, P0301 (cylinder 1 misfiring).

Does pending mean that it hasn't had enough time to test it thoroughly so it only has noticed cylinder 1 misfiring right now, and it may soon register that others are misfiring as well? Or is this a good indication that the ignition coils (which have built in plug boots/wires on them) fixed the misfiring on 2 of the other cylinders and now it really is only cylinder 1?

So to clear it up a bit, see the picture (not the actual car in question). You can see that cylinders 1 and 3 have just the cables going on the spark plugs. Cylinders 2 and 4 have the ignition coils with spark plug boots right on them. So effectively, the spark plug boots have been changed on cylinders 2 and 4, but not 1 and 3.

Do you think there's a good chance that putting new cables on 1 and 3 will clear it? I know, it's a cheap, easy fix, but they live far away, and I don't get over there very often, so I'm trying to troubleshoot as much as possible so I can go over there ready to fix it.

Any other ideas about this problem?

 

[Schwamm]

I have gotten the p0300 code when my O2 sensor was acting up so maybe that's worth checking? It was the upstream sensor, above the turbo on the exhaust manifold.

Have you tested the resistance in the spark plug wires? I've taken a multimeter and tested spark plug wires before and sometimes one has higher resistance than the others, which could tell you if those need to be replaced as well.

 

[paqman]

I have gotten the p0300 code when my O2 sensor was acting up so maybe that's worth checking? It was the upstream sensor, above the turbo on the exhaust manifold.

Have you tested the resistance in the spark plug wires? I've taken a multimeter and tested spark plug wires before and sometimes one has higher resistance than the others, which could tell you if those need to be replaced as well.

Lol, before I even pulled any codes I was telling them that I thought it was going to be an O2 sensor. And when I pulled that code I still thought that may be it, but a mechanic told me that wouldn't be it, and that it would probably be the plugs.

In talking with a few others, I think I'm going to try changing the other two wires this weekend and see what that does. I did hook my multimeter up to the coils (coil on plug remember) and i couldn't really get a steady reading. It was jumping around all over the place. On the old and the new ones. Didn't try it on the other two wires though.

I heard it could also be the EGR valve, but I hope not, cause those are a little costly. Thanks for the reply. I'm hopefully getting over there this weekend and I'll put in the two new plugs and see how it goes.

 

[Dcmason22]

That's funny... Just yesterday, my msp randomly threw a P0300 code too. I've been trying to get around to changing out my upstream o2 sensor because my CEL is usually from a P0131 code. I haven't had any rough idling though, just one suspectious hesitation. I cleared the CEL and haven't had the P0300 again (yet at least). Let us know what you find out

 

[Schwamm]

How funny that I should reply to this thread earlier today only to be experiencing the same problem now....

I have CELs p0300 and p0131, and I tried a new O2 sensor like last time but it did not fix it.... so now I'm trying to figure it out.... different spark plus and swapping out the coil pack didn't fix it in my case either.

 

[paqman]

How funny that I should reply to this thread earlier today only to be experiencing the same problem now....

I have CELs p0300 and p0131, and I tried a new O2 sensor like last time but it did not fix it.... so now I'm trying to figure it out.... different spark plus and swapping out the coil pack didn't fix it in my case either.

In my research some folks say that it could be the EGR valve. Sounds like a pain in the butt to get to though. I'm going to replace the other two spark plug wires (the ones over cylinders 1 and 3). I'll let you know how it goes.

 

[CHIQLES]

if any of you guys have the torque program you can graph out your o2 signal and see if it is spiking if it spikes
meaning zig zags up and down versus goes up flat lines drops down flat lines then that o2 is bad.

 

[paqman]

if any of you guys have the torque program you can graph out your o2 signal and see if it is spiking if it spikes
meaning zig zags up and down versus goes up flat lines drops down flat lines then that o2 is bad.

Dang that's some good info. I just bought a blue tooth OBD2, and the Torque app. All I was using it for is to pull the codes, I didn't realize I could map the o2 signal. Thanks for that. I'm going to try that tonight. I'll let you know.

 

[paqman]

Crap there's a lot of o2 parameters to graph in Torque. What specifically do I want to watch here? Also any other things that might be useful? Pressure, MAF, etc...?

 

[CHIQLES]

you can check all your signals. Its all of matter of when you pick that signal it will tell you how do you want tosee the info best way is in graph mode you will see any wierd trends that way..

 

[paqman]

you can check all your signals. Its all of matter of when you pick that signal it will tell you how do you want tosee the info best way is in graph mode you will see any wierd trends that way..

Do I need to be driving or just engine running?

 

[CHIQLES]

just engine running

 

[CHIQLES]

heres mine top is primary. bottom is secondary after cat signal usally flat if the cat is doing his job

 

[paqman]

heres mine top is primary. bottom is secondary after cat signal usally flat if the cat is doing his job

What are you. Using for your x and y axis? I used time (while stationary) for my x and the 1st or 2nd o2 sensor for the other. My first one seemed to jump all over the place. The 2nd was more steady but definitely not a straight line. It moved slightly up and down and if I pushed on the accelerator it dropped dramatically. After letting up on the gas it slowly came back up.

 

[CHIQLES]

its just live data not the graphing option on the primary page

 

[paqman]

Ah see I'm brand new to this app, and didn't know about that yet. Well the spark plug wires definitely didn't fix it. I won't bother Ober there again for a few days but now I'm curious to view the o2 readings again. Thanks.

 

[unwound]

Are you sure the new coil plugs are good? Just because they are new in a box doesnt mean they cant be bad.

I threw a P0300 and it was a coil plug. I purchased mine from NAPA.

Also just to throw it out there... proper gapping on the plugs?

 

[paqman]

Are you sure the new coil plugs are good? Just because they are new in a box doesnt mean they cant be bad.

I threw a P0300 and it was a coil plug. I purchased mine from NAPA.

Also just to throw it out there... proper gapping on the plugs?

Sorry I haven't been here to give updates. So after replacing all the coils and plugs, I determined it was probably the EGR valve. I was thinking of just taking out and cleaning it, but that sucker is in an impossible spot to get to without taking off the whole exhaust manifold. So she just decided to take it to the dealership and see what they said. And guess what. EGR valve. But of course instead of cleaning it, they put in a whole new one and it cost her about $400. However it fixed the problem. No more shudders, CEL gone.