I have been having a misfire on my truck recently. It is a 2000 Ranger 4X4 with the 4.0L OHV and auto tranny. I have a misfire on cylinder #4 for about ten seconds after I start the truck. I replaced the spark plug and it got better for a week or two and now it is doing it again. The plug looks fouled out. I replaced the rubber intake gasket inserts six months ago but I didn't touch the intake gaskets under the fuel rail. Compression check was 175-185 on all of the cylinders. Any suggestions would be helpful. Thanks

 

brother, im in the same boat. i keep replacing the spark plug because idk what else to do. i have a 1999 Mazda B4000 4x4 4.0L automatic, pretty much the same thing as your truck, and its been doing it since this previous fall. i think it started in september. spark plug looks like its been charbroiled?

 

Yea exactly. I figured the compression check would let me know how serious it was, but im confused (and glad) that is was all ok.

 

so the compression is "good" on your truck? idk if you've seen my other thread, but my frame cracked by the real shock mount, so once its welded up and i get her back on the road, i'll let you know how it goes and we can compare info. but if you get it fixed before then, def. let me know what the h3ll is up with this. all it did was **** me off all winter.

 

Try changing the plug wire.....or swapping it with another cylinder.

 

Sorry, A plug wire will cause this problem!!! I guess you missed the point that his compression is good, this rules out head gasket and/or cracked head!

But, you are in usual form, low reading comprehension again!!

The earlier vintage 4.0L's did have a problem with loose lower intake bolts, which would cause a vacuum leak.

 

my truck does the same stuff good compressure runs great most of the time but when its cold it runs like crap mine is a head gasket cause im useing a but of water like a gallen once every 4 weeks

 

If you are sure your compression is good (you may want to try a cylinder leak down test) then your problem isn't the head gasket, but the lower intake gasket will cause loss of coolant.

 

I forgot to mention I did replace the plug wires two weeks ago. What is involved with the leakdown test? I think that might be my next step. I did notice my coolant resivrior was empty but the radiator was still full. I'll keep a close eye on that. Thats a good idea on doing the pressure test, I'll try that. Also my truck only has 66 thousand miles on it. Thank you all for the info. I really like the truck and would like to get this figured out.

 

Well, I was losing a ton of coolant every week back when the truck was still on the road, and like i said, it is the #4 cylinder.....and its the ONLY one that misfires. Problem is I have a 142,xxx on the truck, and its going in for the "cracked frame" repair. How much will all these tests run me?

 

With the leakdown test, you bring the piston to TDC on the compression stroke, pressurize the cylinder with compressed air, and watch how long it takes the pressure to drop off.....

 

Yea I'll try the leakdown test and keep you all updated. I just pulled the plug out again to look at it and there is definitely oil on it. Im just not sure exactly where its coming from. Thank you all for the input.

 

This is the spark plug hole on the number 4 cylinder. Looks like oil there. How would oil get in front of the plug?

 

i had a 2.9 ford rander which the spark plugs was getting fouled once every couple weeks cause of the piston rings were shot i put some plug defoulers which is like a couple bucks at the auto part store you can try that if you dont know what it is i dont know but you screw the plug into it then put it in the plug hole like normal

 

Do you guys think the head is cracked?