hey Im having problems with my ranger.I have a 1999 ford ranger 4.0l v6 123,000 miles great condition. My problem is when I start my truck after its been sitting for a couple hours or over night it shakes for like 15s and if i put it in gear before letting it warm up it shakes worse. I have changed the spark plugs and wires 2 times and it fixes it for about a month or so and then the shaking comes back. If i let it warm up itll run fine all day. If I put it in gear it feels like it misfires. my cel is burnt out from previous owner. I checked the plugs and all look normal I put the autolite iridium spark plugs in and the only difference i could see is cylinder 4's plug is a little bit more brown then the rest? any ideas why it might be doing this. I leak antifreeze about maybe an inch out of my reservoir in a month so its not a lot. Ive had a radiator pressure test and it didn't drop psi. Thanks for the help

 

Sounds a lot like a leaking head gasket or a cracked cylinder head. I just went through what sounds like the same problem with mine. After running it like that for a few months it started burning coolant pretty quickly so I had to tear it apart right after my manual swap.

Have you checked for moisture under the oil cap? (milky looking oil)
Have you noticed any white smoke or does the exhaust smell like coolant/ have more water coming out than normal condensation?
That coolant in your reservoir is going somewhere is it a tank leak or is it just "vanishing"?

To diagnose it better you can check those things and pull the codes if there are any and reference this post for an idea

https://www.ranger-forums.com/genera...scanner-74975/

But if it is having cold start compression issues until it warms up and runs good once it's warm its likely a coolant leak into that #4 cylinder you said had the gnarly plug. The engine is struggling to burn the fuel in that cylinder with the water until it blows it out the exhaust then when its running better the engine heats up and seals up your leak when everything expands.

To know for sure you'd have to pull the heads or have a good shop do it for you if you got the $$$. Theres a lot of good stuff online on how to DIY though if you're inclined to wrench on your truck yourself.

 

That's What I thoight it was at first. I could be dripping antifreeze through a hose some whrre idk for sure. But I changed my oil and it looked fine not milky and I have checked the cap multiple times and it hasn't had gunk on it. So it started shaking again tuesday night so I took my spark plug out and switched cyl. 4 and cyl 5 plugs and when I started it this morning ot didn't shake? If it was leaking coolant in the. Cyl wouldn't it shake everytime I start itveven if I switch the plugs. Could it be a leaking injector leaking gas in it and the better plug can burn off the gas then eventually it wears the plug out and that's why it shakes after a month of new plugs? And can I check for a bad head by doing any tests? I have put a radiator pressure tester on for about 5 mins and it didn't move from 16 psi thanks for the help

 

it could be a faulty injector causing a misfire...look underneath when it's running and see if your cat's are glowing red hot that would indicate fuel burning in the pipe. I've seen the melted guts of cat's before from this.

However, the loss of coolant with your other problems would be enough for me to guess it was at least a gasket leaking from a coolant port.
Double check your rubber coolant hoses and around the radiator and water pump to rule out external coolant leaks.
The coolant burning in the cylinder would foul up the plug like you were describing. Like I said mine started out just the same way even cracked the insulator a few times. But it progressively got worse I had a pressure test done and it held too. Same thing happened when I switched out plugs. It would run great at first then it would just come back. Eventually it just ran terrible every start and fouled up the injector in my leaky cylinder too.

As far as checking for an internal coolant leak you can try and run a white strip of cloth into that cylinder before you run it cold. Put it in through the spark plug hole and see what it comes out with on it if there's coolant or gasoline you'll know. Also looking for that white smoke/moisture out the tail pipe. It should be visible on cold start if you have compression issues.

Another thing is after it's sat for a bit depending on how bad the leak is you can remove just the y pipe and see if there's coolant dripping out of the exhaust headers I noticed that when mine was bad enough it was dripping when I was doing my manual swap.

heads have to be taken off and pressure tested/magnafluxed by a machine shop to see if their cracked unless its a big crack then you'll see it.

the 4.0 is notorious for cracking heads and your symptoms sound like what's going on.

did you or the previous owner overheat it or run the radiator low/ with a bad thermostat? that could explain why if its a head problem.