P0300 code-cylinder misfire detected. What to try first?

[paqman]

So my check engine light came on on my 97 Escort. I pulled the codes and got P0300. Defenition: Cylinder misfire detected - random cylinders. Explanation: The powertrain control module monitors the crankshaft speed and has detected a misfire condition. Probable cause: 1. Ignition system fault-spark plugs, ignition wires, coil. 2. Vacuum leak 3. injector fault. high or low fuel pressure.

So do I start with the spark plugs and go from there? What do you all think is the most likely cause? I'll do it all myself, just wanna know what I should try.

Thanks.

[denisond3]

Unless you replaced the plugs in the last 10k to 20k miles, they would be the first thing I would change. Next the plug wires, if they are more than 6 or 7 years old. After that I would be looking for vacuum leaks, a lot of crud built up behind the edges of the throttle valve, or a mass air flow sensor that had some cobwebs or dead insects stuck to it.
If you havent tried changing the spark plugs on a Single Overhead Cam Escort before, the #1 plug is hard to reach. I used a 5/8" deep socket with the 3/8" drive in it, and a 10" 3/8" extension that has a special curvature at the square end, which I turn with my 3/8" ratchet. Its called a 'wobble extension' I think, and allows up to 15 degrees of mis-alignment between the socket and the extension. Makes the job very easy. Dont over-tighten spark plugs, I think they only take about 12-15 ft-lbs of torque.

Hopefully the car isnt losing coolant little by little?

[paqman]

Originally Posted by denisond3

Unless you replaced the plugs in the last 10k to 20k miles, they would be the first thing I would change. Next the plug wires, if they are more than 6 or 7 years old. After that I would be looking for vacuum leaks, a lot of crud built up behind the edges of the throttle valve, or a mass air flow sensor that had some cobwebs or dead insects stuck to it.
If you havent tried changing the spark plugs on a Single Overhead Cam Escort before, the #1 plug is hard to reach. I used a 5/8" deep socket with the 3/8" drive in it, and a 10" 3/8" extension that has a special curvature at the square end, which I turn with my 3/8" ratchet. Its called a 'wobble extension' I think, and allows up to 15 degrees of mis-alignment between the socket and the extension. Makes the job very easy. Dont over-tighten spark plugs, I think they only take about 12-15 ft-lbs of torque.

Hopefully the car isnt losing coolant little by little?

lol well neither the plugs or wires have been done in the last 6 years or so. So I'm going to start with that. Thanks for the tip on the #1. That's gonna suck. And I'm not leaking any coolant or anything else.

[paqman]

Originally Posted by denisond3

If you havent tried changing the spark plugs on a Single Overhead Cam Escort before, the #1 plug is hard to reach....

You talking about this little guy?

[denisond3]

Thats the one. On the 2nd. gens that have air conditioning, the low pressure hose & line is also right in front of it.

I dont know if they changed it around for the 3rd gens, but on a 2nd gen. LX, the left most manifold stud is -hard- to reach with the alternator in place. I find it impossible to get the nut on the stud and torqued down, unless the alt. is out. I have worked on 4 Escorts LX's, and two of them didnt have a nut on that left most stud, a 3rd one didnt have the bolt that is supposed to go from the engine accessory bracket into the head. Its also behind the alternator.

[paqman]

Originally Posted by denisond3

Thats the one. On the 2nd. gens that have air conditioning, the low pressure hose & line is also right in front of it.

I dont know if they changed it around for the 3rd gens, but on a 2nd gen. LX, the left most manifold stud is -hard- to reach with the alternator in place. I find it impossible to get the nut on the stud and torqued down, unless the alt. is out. I have worked on 4 Escorts LX's, and two of them didnt have a nut on that left most stud, a 3rd one didnt have the bolt that is supposed to go from the engine accessory bracket into the head. Its also behind the alternator.

Thanks. I picked up a Greatneck 10" flex extender at autozone yesterday, 3/8" drive for like $10. I figure with my setup (no A/C), that should get me in there ok. I also have needed a torque wrench for quite a while, so I think I'm going to pick up one of those. What torque should I be tightening the plugs to?

[denisond3]

The manual says 7-15 ft-lbs for my 95 1.9L. I think it would be the same for any aluminum head using the same type of spark plugs.
I like to clean out the spark plug threads in the head with a thread cleaning tap too. I usually do that soon after I get a car, as its likely its never been done. The dirt from the threads falls into the combustion chamber I guess, but never seems to hurt anything.
I also put a small amount of antisieze compound on the plug threads before I put them in.
I have two torque wrenches. One reads from about 20 ft-lbs up to 15o ft-lbs. The other one reads in inch-pounds, very useful for the smaller bolts, like the ones holding the thermostat housing to the head.

[paqman]

Originally Posted by denisond3

The manual says 7-15 ft-lbs for my 95 1.9L. I think it would be the same for any aluminum head using the same type of spark plugs.
I like to clean out the spark plug threads in the head with a thread cleaning tap too. I usually do that soon after I get a car, as its likely its never been done. The dirt from the threads falls into the combustion chamber I guess, but never seems to hurt anything.
I also put a small amount of antisieze compound on the plug threads before I put them in.
I have two torque wrenches. One reads from about 20 ft-lbs up to 15o ft-lbs. The other one reads in inch-pounds, very useful for the smaller bolts, like the ones holding the thermostat housing to the head.

Yeah, that would be my worry about cleaning the threads is that crap would fall into the combustion chamber. I wonder if there's a way to clean them without. I did get some antisieze compound and stuff as well. I think I'm good to go. Thanks for the torque recommendation, I guess I could have cracked the manual too. Don't worry, I'll do that before starting the job, always do. Thanks again for the advice.

[paqman]

All done. Turns out that #1 plug wasn't a problem at all. Got it out with a regular extension, no wobblers or anything. Had one plug that seized up pretty bad, but tightening it back down a bit, and loosening again got it out no problem. Didn't want to break it, lol. Anyway, so the job is done, and I went to Autozone to ask them to clear the check engine light, and they said they couldn't. I hadn't realized till now that they're not allowed to do that anymore.

He said that after a few days, if the plugs fixed the problem, the code would clear itself. But the kid didn't really look like he knew what he was talking about. Will it just clear itself? If not, how can I get the thing cleared so I can see if it pops up again? I just want to know if this fixed the random misfire.

[jcwit]

Clear your own codes. Disconnect battery for 15 min. to a half hour. Keep track of your radio settings if you want to.

[paqman]

Originally Posted by jcwit

Clear your own codes. Disconnect battery for 15 min. to a half hour. Keep track of your radio settings if you want to.

Well I thought about that, but aren't there some other problems that could cause?

[jcwit]

No, just reseting the radio and clock.

[paqman]

Originally Posted by jcwit

No, just reseting the radio and clock.

Ok, thanks, maybe I'll try that.

[paqman]

Originally Posted by jcwit

No, just reseting the radio and clock.

Sorry to be a PITA, just thought I'd look at the manual, and there are two types of memory, continuous memory codes, and Keep alive memory. For continuous memory codes, it states, "Do not disconnect the negative battery cable to clear these codes; the Keep Alive memory will be cleared and a new code, 19, will be stored for loss of PCM power."

But for the keep alive memory, it says that I SHOULD disconnect the battery for 5 minutes. And then after reconnecting, I have to drive 10 miles so it can all recalibrate.

What the hell. I wanna do this right, and I'd like to know that what I did fixed or did not fix the problem, but I don't want to screw something up by disconnecting the battery. Course, if I were swapping the battery, it would be disconnected for more than 15 minutes anyway, so I guess you can't expect anything too bad to happen.

[jcwit]

Discounting the battery will only reset the computor to the new settings, or in other words the computor will relearn the new settings. Like you say if you would but a new battery in the car more than likely it would be with out power for over 15 minutes, with no harm done.

I just did a tranny flush with LubeGard added and did a disconnect so the computor would learn the new settings and everything works better than before.