Persistent 305 code
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Laughing Gas
Joined: Feb 2006
Posts: 922
Likes: 80
From: Monroe, WA
Persistent 305 code
I have a 1999 4.0 Ranger with 250k miles that throws a 305 ( misfire detected # 5 cylinder) every 3-4 days of everyday type driving conditions. The engine has a rough idle that hasn't changed even though I've replaced plug wires( Motorcraft),plugs(Autolite dbl platt),coil pack, IAC valve, cleaned MAF, and did a vacuum chk(20 inches steady). It doesn't smoke, starts easy and runs great above idle. Fuel consumption and power seem normal. Question is, why does it take so long for this type of code to manifest? Is that in itself pointing at something that I'm just not seeing? Any insight on this would be greatly appreciated, thanks.
Also, is the cylinder in question the actual cylinder of the engine or the one of the firing order? In my case cylinder #5 or the fifth cylinder of the firing order which is cylinder #4 ???
Also, is the cylinder in question the actual cylinder of the engine or the one of the firing order? In my case cylinder #5 or the fifth cylinder of the firing order which is cylinder #4 ???
Fleet Mechanic
Joined: Mar 2014
Posts: 1,272
Likes: 130
From: Missouri
Cylinder 5 should be the middle one on the drivers side. Both of my 4.0 explorers started having troubles around 250k. The timing guides wore down to nothing and fell into the pan causing the trucks to idle poorly. That being said, I think 250k is the upper limit for these engines.
The next thing you should check is compression on cylinder 5. If it's low hopefully its just carbon on the valves. Sea foam might do the trick, wouldn't hurt to try.
Take a look at your coolant too. If it's all milky your head gasket has gone bad.
The next thing you should check is compression on cylinder 5. If it's low hopefully its just carbon on the valves. Sea foam might do the trick, wouldn't hurt to try.
Take a look at your coolant too. If it's all milky your head gasket has gone bad.
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