4.0 liter clunk.

[lifeissomething]

So I have a 92 4.0 with either 88k or 188k, judging by the rocker arm wear and the piston sleeves that's actually 88k. The truck is 4x4 and a five speed. I just replaced the heads, but this was happening before, when I took the truck home with cracked heads the day I bought it.

When I press on the gas hard at low speeds it sort of clunks before it goes. Clunk, and then it picks up. Also, when I pick up speed slowly in a high gear it does the same clunk at regular intervals, but with a pretty good span in between them. Clunk........Clunk..........Clunk...... Clunk........

It seems to happen when it's at running temp. Also, there was probably still some air in the coolant. These newfangled things with sensors baffle me, could that have something to do with it? Or for that matter, having had oil in the coolant, etc... etc... The check engine light was on after I replaced the heads, but went off after ten miles or so.

Thanks.

 

[ChrisHelvey]

I know these newfangled things seem daunting, but really they are quite straightforward - even less of a "black art" than carburetors.

I suggest getting a service manual and following the procedure for checking what codes are stored in the Electronic Control Unit.

A really short explanation of how these work may help:
The control unit is constantly gathering information from the different sensors about air density/flow, coolant temperature, O2 content in the exhaust, and throttle position (those are the main ones) and, from this, makes a determination about how long to open each fuel injector to control mixture (it quickly pulses.) Depending on the vehicle it can also control timing.
It's all math and lookup tables in the ECU at that point. That is one reason they are so consistent, because they constantly adjust.

When something is "Off" it gets stored in the ECU memory and if you ask it nicely, it will tell you what is wrong (or at least give you a clue as to what to look for.) The codes may say something like "Rich mixture on bank #2" or "O2 sensor #1 below minimum voltage."

This info can help you see what may be going on and what direction to go.

You can post the codes here and someone may be able to give some insight.

Good luck.

 

[trail B2]

This link from a fellow Ranger Stationer helped me turn the corner on EFI.

http://fordfuelinjection.com/

 

[Nhaz]

Try greasing the slip yoke on the drive shaft. they get dry and they go clunk as you step on the gas pedal. Generally you hear it at low speeds, and it can be loud and be felt through the whole truck.