I have a 96 ranger 2.3 L w/ a 5-speed manual transmission which has recently developed any annoying habit of clunking which appers to come from the engine; however, it's difficult to tell as it requires 2 people to create the sound. Here's what I have been able to gather so far:

The engine will run fine except when it is under a large load at start up. Every weekday I make the same commute and the engine will run fine till I exit the freeway at whic hpoint the engie will make a clunking sound in all gears;it's important to note that prior to exiting the freeway the egine is kept ~ 60 MPH in 5th for ~ 15 - 20 minutes. This clunking usually begins after ~ 2 seconds of acceleration and becomes louder as the engine speed increases.

I have on occasion been able to force the engine to make the sound while parked however it has not been consistent and it has always been when i've ben alone so there's no way for me to listen for the sound outside and hold the accelerator.

Additionally that I have noticed is that whe the engine is under a load in 5th it is possible to hear a sound which sounds like tapping values but it may be from the transmission.

I have noticed that during the course of diagnosing this that my gas mileage has increased for 22 - 23 MPG to 24 - 25 MPG. Just tonight I was finally able to to retrieve an error code from the engine P 1131 (o2 sensor lean AU).

Might anyone know the possilbe relation between the symptoms I have expirenced? It doesn't seem that a clunking would come from just an O2 sensor, any hypothesis would be appreciated.

 

Welcome to Ford Truck Enthusiasts!

Is it a clunking noise, or more like a light knocking/pinging noise? It almost sounds like you are experiencing spark knock. If it is a pinging problem you have, then a bad 02 sensor could possibly affect that situation, but I doubt it would be the sole cause.

Does your engine make the noise when it's cold?

When you are cruising 60 MPH on the highway, you don't hear it then?

 

I thought it might be a ping situation so I have tried a Higher octane fuel as a result, thus far while using 93 octane there has been no notable change. As far as while crusing I have noticed a slight sound but I have yet to determine if it is the clunking sound.

 

just for the heck of it, does it clunk when letting up on the gas or pressing the gas while driving or shifting? just in case you might have a ujoint going.

 

check the motor mounts

 

I found the problem this morning twas not the engine @ all. Turns out the purge Valve for the EECS system was moving around because the plastic clap which holds it next to the battery broke. It finally did it when someone was with me and so was able to see it moving and tapping against the fender. The lean engine condition is still there but now that the clunking is out of the picture as a symptom it should be much easier to diagnose the exact problem knowing there is no clunking from the engine.