I have a '94 Ford E-150 with a 5.0 It has about 280,000 miles on it. Around town, the Check Engine Light comes on sometimes, but does not seem to affect performance unless the engine has been running for awhile.
On long trips, like after an hour or two, the engine will seem to bog down, RPMs will drop. The ECL will come on around this time. The speed drops, and throttle needs to be increased and at a certain Point, either from dropping down a gear or "pushing" past the bog down point using the throttle, the engine will accelerate and regain the lost speed. Sometimes doing this will cause the engine to "cough" out of the intake.
After this starts happening, the interval between these bogdowns decreases. Once a bogdown happens, gradually giving it more gas won't increase rpm, the van may slow down further until you give it so much gas that it drops a gear to higher rpm.
Of course, this is a real problem when in first gear, almost no power to get going.
When all this starts happening, the onset of the bogdown is gradual, and the throttle and/or downshifting needed is mild. As they become more frequent, the engine bogsdown harder and it takes more throttle and hard downshifting to regain speed.
Eventually I pull off and let the van sit with engine off for 10-30 minutes and resume. This works for awhile, maybe an hour and then it begins again.
I've replaced the air filter, plugs, wires, distributor and the catalytic converter. Additionally, I think it's the lifters that rattle at higher rpm, don't know if it's related or not. Otherwise, cranks right up and runs good, smokes blue exhaust a bit.
