spark plug question

i think you have more than one problem going on there. the two cylinders from the plugs on the right might indeed be running lean, but they're also burning oil. that is one whole lot of ash accumulated, and beyond the threads, the plug bodies are wet with it. it would explain why it runs fine on new plugs and misfires when the ash accumulates - weakened spark insulation at idle when voltage requirements are high.

if you don't want to fix the oil situation, i'd run some injector cleaner through it and just keep changing the plugs - they're cheap enough. and the codes will remain fine until the catalytic converter/oxygen sensors get ashed up and lose efficiency.

By the looks of the plugs, you have an oil problem. Those were changed after 5,000 miles? Then by their appearance, you also may have a minor water problem. The only way to know what is causing the problem is to tear down the block and inspect for hairline ftactures.

Your miss could be as simple as a defective spark plug.. Are these the correct plugs for your vehicle? Have you replaced them several times and each time they last about 5k? Is your valve cover leaking?

I'm having a similar problem as well on my '98 Plymouth Breeze 2.4L. I have an occasional miss at idle and changing my plugs corrected this problem, but 3 weeks later the miss has returned. I may try another set of plugs (cheapest fix first) and see if I may have a defective plug.

The plug on the left looks like it came from a cold cylinder that hasn't been firing at idle. Have you checked compression?

Is the miss just one cylinder going "pfft pfft pfft" at idle and then it smoothes out when revved.

What does "It scopes out fine" mean? Did you looked at the secondary using an Oscilloscope and see no difference in the spark form on all cylinders?

-jim

Thanks for the replies. From the questions asked here is more info to answer them and see if anyone has further thoughts.

The engine runs like new power wise, other then this miss. It doesn't burn any oil between changes or 3000 mile+. Only needs more coolant perhaps once or twice a year, never blows white smoke or any other smoke on startup. The shop that "fixed it" last year said they could find no problems when I brought it in as it was running fine that day. The ignition looked "fine" by whatever test equipment they used. I brought it back two days later because it started acting up again. This time they could occasionally experience the problem while driving but could still find nothing when they "tested" it. They did a fuel injector cleaning and gave it back to me. It ran the same with the occasional miss. I brought it back. At this point it had some bosch double plats in it that I had put in about 5K earlier. The mechanic didn't like the bosch plugs and said he thought it was the plugs even though they "tested" OK. So I told him to go ahead and put whatever plugs he liked in it which as Motorcraft copper core. When it got it back it ran fine and continued to run fine until recently when it started the same miss again.

Here's a more complete description of the "miss". Sometimes it will idle ok but when you start up you can feel a miss that feels like a single cylinder. That may persist till you get it up to about 2000 rpm and then it goes away. On the freeway it's fine, kick it into passing gear and it's fine. Sometimes it will have what feels like the single cylinder miss but as you accelerate normally, say from a stop light, it gets to 1200 rpm and feels like all of a sudden 2 or 3 cylinders are missing and it losses power significantly. This may last for a few seconds and then it clears up and goes back to a single cyl type miss and then goes away. I thought it was ignition till I read the below...I'm on the road now so I'm just hopping three new plugs will eliminate the problem for a few weeks.

From the net....

I had the same problem with my '95. Low RPM miss I couldn't track down. Did all the usual checks/replacements of vacuum leaks, plugs, wires, coil pack, sensors, etc... Then I decided to check the resistance I was getting off of my injectors after none of that resulted in the miss getting fixed. BINGO! even though I wasn't getting a CEL, the truck was running lean, but not lean enough to throw a code. I had 2 bad injectors, and another 2 reading higher than normal. Normal range is between 13 and 19 Ohms. One was way off intermittently at 54 Ohms, and another was just over 24. the other 2 were just about 21 Ohms, definitely out of spec.

So I ordered a new set of 6 ( what is the point of just replacing the ones that were bad, seeing the others could go at any time as well) from a place online. $120 for all 6 shipped, can't beat that deal anywhere! And they are FORD parts.

Anyway's, after getting them all installed (about 2 hours of work total) The miss was gone and has been running like it was brand new ever since.

I was ready to start throwing parts at it

Have you checked your fuel filter? Do you have water contamination in the fuel? Try changing out the fuel filter and see if the problem goes away.

It is not uncommon to get contaminated fuel -- especially if you fuel up during or shortly after (

Ashton Crusher wrote in news: snipped-for-privacy@4ax.com:

have you replaced your plug WIRES? distributor cap/rotor? the wires do get old and begin to break down. Then your plugs will misfire.

Wires are only a couple years old. Took it out for a drive tonight with the three new plugs in it and it purred like a kitten, not a single miss. When I get home I'm going to pull one of the plugs on the other side and see what that side looks like but it seems that side is OK.

fine, but just like jim is saying, don't dismiss the wires/cap being dodgy. they may be making connection now because you've just manipulated them fitting the new plugs, but it doesn't mean they're 100% good. just like being only 2 years old doesn't mean they're good.

jim beam wrote in news:jov6q7$j92$ snipped-for-privacy@speranza.aioe.org:

constant pulling of the plug wires can damage the center conductor/connection,usually at the ends. or there could be an insulation break,allowing your spark energy to go astray,under certain conditions.

Or a cheapo dist.cap/rotor could cause problems.

indeed.

yup. but if it's a rotor, it's usually a problem affecting all cylinders, not just one.

On this Vehicle, the explorer, there is no distributor, just a computer and coil pack and pickup coil down by the harmonic balancer. One of the reasons I'm leaning toward the fuel injectors as the underlying problem is that in the past when I've had ignition system problems they were the worst at high load/high rpm. In this case the problem goes away at high load-high rpm. I wonder if what I'm perceiving as a "Miss" is really knocking from too lean a mixture.

I'd replace the wires first. That is your next weakest point. Since you moved the wires your problem has stopped for the time being. I'm having the same issue w/ my car and I'm gonna replace the wires next.

Ashton Crusher wrote in news: snipped-for-privacy@4ax.com:

any codes in the ECU? there are codes for coil pack malfunctions.

In message , Jim Yanik writes

I know it's considered out of date and very seldom practised nowadays, but "Pinking" or pre-ignition can sometimes be caused by a build up of carbon near the plug in the head which glows red hot as the engine gets warm. A good 100mile blast as hard as you can down a motorway normally burns that off. The usual reason for carbon buildup is if the engine is under utilised, to lightly loaded or never given for more than a few mile as a time.

These plugs dont seem to have carbon on the electrode areas. They have a white slag of mineral deposits, it would appear. There is also a little red color to some of these, which could be iron/rust.

Nontheless, these deposits can cause the pinging you describe in the same way as carbon deposits.

But where is this coming from? If antifreeze were bleeding into the cylinders, it might give this sort of scale product. Some kinds of oil additives might also burn off white like these deposits.

5000 miles is too short a time to use up a set of plugs traditionally. Something here doesnt quite fit.

What was the Bosch part # installed? Maybe the wrong plugs are installed as well?

I just started here, so excuse me if this was covered. Good point about which plug. In my experience OEM is best. Those plugs look oil fouled. Not bad though, and it's running good enough to burn off most the oil. Could be blowby, could be valve seals. For valves seals oil gets sucked in at higher vacuum, backing down on speed or idling. I had a Ford 352 that would use a quart every 500 miles in local driving. Went on a 3000 road trip and didn't use a quart. Pissed me of because I had completely rebuilt it, but the shop I took the heads to screwed up on the valve seals.

Without the miss the plugs may stay clean. Maybe. You don't mention miles on the engine. I've never had luck pinpointing bad injectors. Just did OHM tests though. Always bit the bullet and put all new in. '92 is getting long in the tooth. You might want to run a compression test before you throw money at it.

I've just had a quick look, the left one looks to be OK the right two definitely look like lean mixture to me.