CYLINDER 4&6 MISFIRE - 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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Old 01-10-2013
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Icon4 CYLINDER 4&6 MISFIRE

i have a 97 4.0 ohv. recently it started misfiring on 4 and 6. it idles rough, studders and shakes very bad under acceleration, lacks power..

brand new coil pack. brand new sparkplug wires also. the plugs only have 2000 on them. recently upper intake manifold gaskets were replaced. cleaned MAF (just to say i did). Ran seafoam. New fuel filter. new KandN air filter. i had a shop run a scan on it and all that it was showing was the 4 and 6 misfire.

It seems to go through coolant. sometimes it leaks externally and other times it wont... blown head gasket? faulty injectors maybe? cant think of anything else. help or similar experiences please.
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Old 01-10-2013
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Can you have the pressure checked in those cylinders?

Is it blowing white smoke out of the exhaust?
Its showing signs of a blown head gasket.
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Old 01-11-2013
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If you have bubbles in the expansion tank it is likely to blown head gasket. Check you oil filler plug. if you have white emulsion - 100% head gasket.
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Old 01-11-2013
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no white smoke it doesnt seem. but come to think of it... it did have a whitish-oily colored foam on the oil cap. any tests i can perform to check before i tear into the engine? just want to make sure
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Old 01-12-2013
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Quote:
Originally Posted by Fox Ridge Ranger View Post
no white smoke it doesnt seem. but come to think of it... it did have a whitish-oily colored foam on the oil cap. any tests i can perform to check before i tear into the engine? just want to make sure
Yes, whitish-oily colored foam - the first sign of burnout head gasket or cracked cylinder head if it was overheating. Check you spark plug in 4 and 6 cilinder. If spark plug electrode is white - verify gasket.
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Old 01-13-2013
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what would you consider overwhelming? i was able to wipe it off with one finger. im going to have it smoke tested, but i should have some spare time to check 4 & 6 plugs soon.. ive been getting crappy hours at work.
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Old 01-13-2013
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Some white foam/milky stuff on the oil fill cap is completely normal. Thats just from condensation. the place you DON'T want to see the milky mixture is on your dipstick. You could also take the oil fill cap off and look down in there with a flashlight to see how it looks.
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Old 01-13-2013
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I would have to start checked presence of bubbles of gas in the cooliant tank.
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Old 01-13-2013
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Originally Posted by Fox Ridge Ranger View Post
what would you consider overwhelming? i was able to wipe it off with one finger. im going to have it smoke tested, but i should have some spare time to check 4 & 6 plugs soon.. ive been getting crappy hours at work.
Don't smoke test it. Pressure check the cylinder.
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Old 01-21-2013
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The 4-6 misfire may be caused by crossed wires. The cylinders are logically numbered, but at the coil pack they are not. I am doing this from memory, so I don't want to get too detailed. I tried to look up the difference, but I couldn't find it. From memory, it seems the coil pack goes 1,2,3 (front to back) on the left side as you face the vehicle. On the right side it is numbered 4,6,5 (front to back) as you face the vehicle. I hope I have that right, but the bottom line is they are different and you need to make sure to get them right. Many are not. Hope this helps.
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Old 01-30-2013
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hey everybody. sorry i havent been on recently for an update. Turns out, was not a blown head gasket. Everything was normal now that i have looked at it in detail. The wires were correct @IslandFord, thank you for the reminder tho. I pulled 4&6 plugs Saturday and what i found didnt look so well.

The plugs were covered in a good amount of oil. I had my friend do 4,5,6 plugs for me. They were NOT even close to being gapped correctly. I have replaced all of the plugs now and the truck is running great.

So my question is.. would spark plug gap being WAY off cause oil buildup and glazing of those plugs?

Thanks for input everyone
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