Spark Plugs keep going bad - Page 2 - Ranger-Forums - The Ultimate Ford Ranger Resource


4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

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  #26  
Old 10-24-2007
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FWIW: A few years ago my '98 was sipping coolant and the #4 plug was fouling every couple of thousand miles. I went though the same process trying to nail down the cause. Finally, I had a used oil analysis (UOA) done and it confirmed that coolant was getting mixed into the oil, which in turn confirmed that the problem was not fuel or ignition-related. I replaced the lower intake gasket and I have not had a misfire since.

See: https://www.ranger-forums.com/forum2...ad.php?t=44937
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  #27  
Old 10-24-2007
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wydopnthrtl: As I'm not really sure which plug caused it this time, I've included the pictures of the plug I pulled the LAST time this happened. Replacing that plug (came out of #4) "fixed" the problem until now. Replacing the plug in #4 this time made it worse (or so I thought) and last night I put the plug that had been in it, back in. It didn't get any better, so I'm pretty sure it had nothing to do with #4 this time around. So anyway, here's the pictures of the #4 plug from LAST time that made it better by replacing it.

http://farm3.static.flickr.com/2088/...51690536_o.jpg
http://farm3.static.flickr.com/2173/...f6be86c0_o.jpg
http://farm3.static.flickr.com/2087/...3937d7c8_o.jpg
http://farm3.static.flickr.com/2007/...7edcc9b8_o.jpg

rwenzing: So, it has problems at multiple ranges. Let me see if I can describe all of those situations with some clarity.

When the engine is cold (even more some in cold weather) it just runs like crap...idle, under load, whatever. It DOES seem to get worse when it's under load but, is it just more noticeable? Maybe. Once I get up to highway speed it seems to get marginally better.

When the engine get's to running temp, it definitely smooths out but stil misses. In that case, it misfires randomly (not running rough anymore). When I lay on the gas I notice it the most. If I'm cruising or get above about 2,500 RPMs it smooths out. I'm betting that it's still misfiring, just not as noticeable since the rest of the cylinders are producing so much surplus power at that point as well as the inertia of the engine would tend to mask the misfires.

I sprayed starter fluid to every part of the intake manifold & hoses that I could get to last night. No rev. It was dark & I was ready to get to bed, so I may not have gotten it good. I'll try it again this evening when I get home from work.

Rockledge: Yeah, I read your thread (along with countless others, 6 hours on here Monday night). Do you remember how much it was? I looked on their site when I saw your thread & they had all kinds of different tests with different prices. I see the price list here.

http://www.blackstone-labs.com/tests_price_list.html

And then I'm assuming all I really want is the Standard test? Did you get any of the extra tests to determine AF getting into the oil? I checked the AF level this morning & it looks good.

I reset the computer last night to see if I could get it to throw a code. I'm not sure if it will, seems like the truck has to be about to die before it'll indicate a misfire.

I definitely appreciate everyone's help...this has been a phantom for some time.
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  #28  
Old 03-04-2008
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I know this is an old thread but now the same thing is happening to my 2000 ford ranger 4.0. About 6-7 months ago it threw a code of po304, I went ahead and replaced all plugs and wires, (I used Autolite Double Platinum) and it was running great again. But then 2 days ago, it started acting funny again as the previous posters complained of. I went ahead and changed out the plug started it up and still idled rough, shaking, and then when I drove it, it threw the same code again. So, now what should I do? replace the coil? or is it the injector?

help please

rok
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  #29  
Old 03-04-2008
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Ok, I apologize for not updating this thread. The last time this happened I bought a new set of plug wires & went through the available amount of money that I could spend on it at the time. That didn't help so I replaced the #4 spark plug again. "Fixed" it. So my thoughts that it wasn't #4 were due to me putting in what I thought was a good plug, but it was used. I was VERY irritated at the whole problem & wasn't thinking about it clearly. It's been running fine ever since. Is it fixed? No, most certainly not. The next thing I'm going to do it replace the coil pack (when it happens again).

roksngr: Did you replace the plug with a brand new one? You're situation happened to me last time (as noted above). Buying one brand new plug & installing it worked much better. But I don't think that'll fix it for good. Like I said, I'm leaning toward the coil pack, but haven't replaced it yet.

For the record, I tested the coil pack with a multi-meter & compared it to the shop manual & it was out of range (high ohms...somewhere in the neighborhood of 15 ohms...I'd have to go back & check my notes to tell you for sure). But the confusing part is I checked the one in my wife's 2000 Explorer 4.0 SOHC & it was about the same. Then the guys at autozone gave me their specs & it was within range. Now...granted, that's autozone. I'm not sure I would believe them over Chilton & Haynes.
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  #30  
Old 03-04-2008
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Yes, replaced it with a new plug, still acted the same way. I'm thinking it's got to be a injector. I threw in some redline injector cleaner, just for s**ts and giggles, but I don't want to drive it around when it's acting like this. If I throw in a new coil pack and it doesn't help, then I'm out my $ on that. (No returns)
I'm 1/2 tempted just to take it to the dealership 'cause I don't want to keep dicking with it.
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  #31  
Old 03-04-2008
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It's highly doubtful that the problem is related to the coilpack. I'd spend my money on a UOA before buying any more parts. Cheap and easy to do:

http://www.blackstone-labs.com/standard_analysis.html
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  #32  
Old 03-04-2008
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roksngr: I understand the frustration. If you do, would you mind posting back on here what they determine?
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  #33  
Old 03-04-2008
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definitely
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  #34  
Old 03-17-2016
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number 4 nisfire

Have the same #4 plug misfire on my 2000 ford ranger 4x4 4.0L. I decided to look up problem. I get the P0304 code. When I replace trhe plug every several thousand miles, it runs fine again. Plug looks clean but it just must be burned out. At times, I do get the P0171 and P0174 system too lean codes too. I replaced the coil pack to no avail. I believe I might need a hotter plug or fix the fuel injector maybe.
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