Ok, yesterday I changed the fuel filter, air filter, and TPS in my 92 f150 5.0. I also cleaned the throttle body as it had a lot of black buildup in it. First question: When looking into the upper intake, it had a lot of black buildup that looks like it needs cleaning as well. How do I go about doing this? Do I need to worry about it?

Also, with the above maintenance performed, the truck has a good idle when in any gear. Even the air cutting on/off will not change it. However, when in park the engine bumps up in rpms instantly and then will go back down to a lower rpm level (it does this on about 5 second intervals). Air conditioning is off. Anyone have any suggestions on this?

Thanks in advance for any information.
Matt

 

Have the upper intake professionally cleaned by a shop that uses BG Products.

Get a Haynes manual & test your MLPS - they're known to go bad from water intrusion, and there's an updated part available. You can read the TSB about it in this thread.

 

Would this cause the truck to have a high idle?

 

Did you read the TSB? Read the one about the IAC, too.