Lope at Idle, Unresponsive Throttle on Road, Slight Engine Surge (all intermittent)

[TexasAggie]

My brother in law has a 99 7.3L that has had a slight engine surge while running down the road for a while. The truck would just shake a little. Now it has started to lope at idle on a cold start. By cold start, I don't necessarily mean cold outside. We are in San Antonio... Around the same time the engine started loping, he would notice that the throttle would not respond until he steadily depresses the pedal. Some times he has to left off the throttle and then press it again to get it to respond. Sometimes when he puts it in reverse the rpm drops, but the engine doesn't die. Once when he let off the throttle to come to a stop the engine did die, however.

Any ideas?

Thanks.

[TexasAggie]

Nothing?

[jearl]

I have replaced my pedal assembly a couple of times and some of what you say happening happened to me. erratic response and under light throttle a bit of a bucking feeling. the TPS (throttle position sensor is in the pedal assembly and on the 99's can get dirty and also the contacts get a bit burned out. I have had some luck just removing and squirting some WD40 on the contacts but souds like it may be on the way out. You can purchase these from sponsors-I bought mine from Wabash Ford in Indianapolis for about 80.00 good luck-Jim

[TexasAggie]

I'll see if he has a multi-meter to check it out. I'll also have him check the connection.

[WayneB]

Not sure he'll see anything with a multimeter. He would need an oscilloscope, to see the sine wave as he pushed down on the pedal.

Wayne B