ok, need some help on this one. The truck runs great most of the time. But when I'm driving up hills at freeway speeds it starts running rough. This starts about 10 seconds after I start climbing a descent grade. First the exhaust tone changes from deep and throaty to light and airy. If I stay on gas the truck starts to lose power and run rough. If I let off the gas the problem quickly dissipates. Also this only happens above 2500 RPM. If I change gears (I have a 5 speed manual) and lug the truck up hill at lower RPM it does not do this.
I thought the fuel pump or rail regulator might be going bad so I tapped into the fuel rail at the cold start injector line and rigged up a mechanic fuel pressure gage in the cab. Fuel pressure is solid. Definitely not that.
Because of the way the problem fades in when I'm on the gas and fades out when I let off, I'm thinking it's the timing. I had it advanced before the problem started. Now I reset to factory 7deg, but the problem still exists. I do not fully understand how the 3FE timing advance works. Could something have broken in the distributor? Distributor vacuum filter plugged? What do the wires going into the distributor do? Does the ECU control the timing on the 3FE or is it purely mechanical?
Thanks for your help.
I thought the fuel pump or rail regulator might be going bad so I tapped into the fuel rail at the cold start injector line and rigged up a mechanic fuel pressure gage in the cab. Fuel pressure is solid. Definitely not that.
Because of the way the problem fades in when I'm on the gas and fades out when I let off, I'm thinking it's the timing. I had it advanced before the problem started. Now I reset to factory 7deg, but the problem still exists. I do not fully understand how the 3FE timing advance works. Could something have broken in the distributor? Distributor vacuum filter plugged? What do the wires going into the distributor do? Does the ECU control the timing on the 3FE or is it purely mechanical?
Thanks for your help.