'99 4.0L cylinder #4 misfire help???

[atomicjoe23]

I have a '99 4WD extended cab Ranger with 142,000 miles on it. . .I replaced the plugs, plug wires, and coil pack 2000 miles ago; after about 1000 miles cylinder #4 started to misfire. . .I replaced the plug and it was fine for another 1000 miles at which point (this morning) it started to misfire again, only worse. I replaced the plug again, but this time it didn't fix the problem.

I'm getting ready to compare the resistance between the 3 used plugs and a brand new plug, check the resistance on #4 plug wire, and make sure the plug is actually producing spark (ground the plug with the engine running and check to see if it's sparking. . .wish I had one of those new spark testers that you just clip around a plug wire).

Is there a way to check the coil?

Has anyone else ever had this (or similar) problem??? I thought maybe I should check the fuel rail pressure, but I would think this would affect more than just cylinder #4 and changing the plug wouldn't have fixed the problem the first time. . .maybe the injector is clogged. . .I don't know.

I need to get this fixed this weekend

Thanks for the help!

 

[atomicjoe23]

OK. . .I may have changed the wrong plug out this time. . .have to double check that real quick. . .

. . .but that still doesn't reveal the root problem. . .why is this happening, these plugs should be lasting around 60,000 miles I would think (at least that's how long my last vehicles plugs would last before they needed changing).

 

[atomicjoe23]

I did get the cylinder numbering swap and changed the #5 plug instead of the #4 plug. . .changing the right plug got rid of the misfire, but I don't know for how long.

The plug had a little oil on it. . .not a lot, didn't smell like burnt oil (fresh oil change 2 weeks ago). . .and the truck doesn't burn oil (at least not enough to notice it on the dipstick between oil changes). . .but it was there, could have been fuel, but it didn't smell like fuel. Other than that, the plug looked completely normal. . .color looked fantastic in fact.

 

[alwaysFlOoReD]

Did you try pulling codes to see if there are any pending?

 

[atomicjoe23]

No codes. . .the computer doesn't seem to be very sensitive on this truck. . .I will feel the misfires before the check engine ever comes on. . .weird based on my experience.

 

[06RangerXLT]

That's normal. My truck ran like it was camed, loaping, before I got a CEL. I found when o had a missfire, that it was the boot not the plug. Spray some water on the boot. If you see a blue spark, you need wires.

 

[atomicjoe23]

What's a CEL???

 

[CHKNFKR]

Check engine light

 

[atomicjoe23]

What should the resistance reading for the plug wires be. . .my Camaro manual told me what the resistance reading for the plugs should be ("x" ohms per inch of plug wire) but the Ranger manual doesn't. . .and I don't have the Camaro manual anymore to see what they said it was supposed to be.

I sprayed starting fluid around the upper intake manifold, the air intake tract, and the vacuum hoses that I could identify and the engine never revved. . .so I don't think it's a vacuum leak. . .

. . .I'll be changing the fuel filter ASAP because it probably needs done anyway.

Can I clean the MAF with Electronic QD cleaner without damaging it???

 

[cr_the_machinist]

Be sure the product you use does not contain silicone. CRC makes a MAF cleaner as well.

 

[atomicjoe23]

Latest update. . .

Re: '99 Ranger 4.0L V6 is sick. . .help???
I changed the fuel filter and I made it about 1500-2000 miles without any problems. . .got a few small misfires this morning on the way into work. . .gonna pull the plug and inspect it after work, but I'm gonna guess that it will look fine. I'm gonna swap in one of the old ones I previously pulled and see if it works. . .if it does that will eliminate the plug as the problem as well the ignition system. . .leaving either the MAF sensor, the fuel injector/injector O-ring, or the previoulsy mentioned cracked head.

Anyone have any info on how to check for the cracked head using a compression test. . .I would like to be able to check for this without pulling the head.

I'm gonna grab some cleaner to clean the MAF today after work as well. . .

Also, how would the fuel injector be related to this problem? I could see it causing a misfire if it just didn't work, but what's confusing me is that changing the plug fixes the problem (at least temporarily). . .the only thing I could think of is if the seat of the injector is dirty and it leaks by resulting in the plug wet enough that it won't fire after a sufficient period of time. . .does that seem like it would make sense???

Thanks!

 

[atomicjoe23]

I pulled the plug after work today and threw in one of the old ones that I gave me trouble. . .thought maybe after it dried out it would be OK. . .

. . .WHOAAA, it drove like CRAP!!!

Stopped and pulled the plug and compared it to a new one and I hadn't even noticed before that the electrode (tip coming out of the ceramic insulator) was getting eaten alive!!! It looked like someone had chucked it up in a lathe and turned it to half of it's original OD!

Would a lean condition in that cylinder cause that??? If so, then I should probably start looking at the fuel injector as the culprit right???

At least if that's the case the injectors are only $36 for this truck. . .

Thanks for the help!

 

[Earl43P]

http://www.fordfuelinjection.com/?p=82

Swap injector to another cylinder, or replace it.
I'd clean them all.

Why would you put a known bad plug back in?
The fine wire platinum plugs do have a small electrode.

If you are going as far as replacing an injector, you might as well replace the intake gaskets, upper and lower.
They tend to leak, sucking air.
Could explain ONE cylinder running lean.

 

[alwaysFlOoReD]

I'm not sure that it's possible to check for a cracked head with a compression tester but you can with a leak-down tester. If your compression tester isn't a cheap ass one you may be able to convert it into a leak-down tester. A leak-down tester is a fitting going into the spark-plug hole with one or two gauges [depending on type, two being better IMO] and a valve to control air pressure. Apply 100 psi to the tester at top dead center for cylinder being checked, and look to see percentage of leak, 5-10% being really good,10-20% average, and over 20% not so good. Listen at rad,carb or intake, exhaust, oil fill, and any others I may have forgotten for sounds of air leakage. With a compression test, this will give you a very good idea of what shape the engine is in.
Good luck,

Richard

PS; I'm self-taught so double check my info, I've been known to be wrong sometimes, and or out-of-date on procedures.

 

[atomicjoe23]

Thanks guys!

Earl, I was planning on trying the injector swap. . .as far as putting a known bad plug bad in. . .I didn't notice that the electrode was damaged initially, so I thought that it was just a wet plug. . .turns out it wasn't, and by doing so I noticed the damage to the plug, checked the other plug and saw it had the same damage so that clued me in that the ignition system isn't the culprit. . .so I know to move onto the fuel delivery system and/or do some more thorough leak checks.

Thanks for cluing me in on the leak down test vs. the compression test AlwaysFloored.