Audio Systems: Ford am radio, resistor type, work radio

Question
Hi Garry,
I don't know if this is an appropriate question for you but I think you'll know the answer. I inherited a 1989 Ford Ranger pick-up from my dad with the basic, standard, crummy am/fm cassette set-up. The only time the AM radio works decently is when the motor is not running. It's OK then. While I'm driving down the road, reception is really poor...unless I shut down the engine..in which case, it's fine.

I know the antenna is hooked up because it's worse when it's not...so what do you think? Thank you very much!
By the way, FM reception seems to be quite good!
Charles

Answer
replace the plugs and spark plug wires with resistor type. don't get the cheapest, as these won't be any better. if that doesn't work, radio shack has noise supression kits that work quite well, but you have to try wires and plugs first. also make sure a lead goes from the negative side of battery goes directly to body.