Timing problem

[2manydsls]

My 92 e-350 van has a problem which I will try to explain. When driving at freeway speeds IE 70 mph and above, the engine will really rattle. This only occurs when the throttle is at about 1/8 to 1/4. Slight deceleration. When out of overdrive it does the same thing at around 60 mph and above. More acceleration or deceleration and the rattle stops. I'm sure something is advancing the timing under the above conditions. Other than the noise it doesn't seem to cause any problems. Any ideas? Thanks in advance.
Ross

 

[EvergreenRanch]

well take what i have to say with a grain of salt, but the only way that your timing could be advancing is if the bolts on the IP housing were loose, and the symptoms would be WAY worse. lets hear a little more about symptoms...... what and where does the rattle sound like? will the same thing occur if parked and revving in neutral? is it violent shaking back in forth, or does it feel like the engine isnt getting enough fuel. what rpm's is it occuring at...etc.

 

[2manydsls]

I did check the ip bolts and they were tight. I could not get it to do it in neutral ,although i didn't try too hard as I don't like to rev an engine with no load, however, it will do it in low. It happens at about 2500 rpm and above. The only indication of a problem is the loud rattle. It sounds like valve train noise, pinging. No other problems before, during, or after. It did seem to be easier to make it happen when locked in low gear. When it is doing it if I give it more throttle it stops. Also, if I let up completely on the throttle it stops. Its definately coming from the engine. I'll be leaving the computer world for 5 days starting tomorrow so won't be able to respond till next Wed. or so. Thanks again for any help.
Ross