Redridermx88

i have a 97 with 175k on it and when i bought it from a buddy he told me the Throttle position sensor was replaced because it made a weird horn like/ howling sound when the truck is up to operating temp and you are coasting to a stop sign. It doesnt always do it but if i tap the gas it goes away till i coast again. It will keep making the same sound even after ive stopped and put it in park untill i shut the truck off. I replaced the TPS and had no luck. Any ideas where I should look else where. Its coming from the intake and you can really hear it through the K&N filter when its idling. No engine codes are present

ghostrider

Are you sure that you replaced the tps. The iac valve is what is causing the fog horn sound at idle.

98redf150

Does it have an entire k&n system?

Redridermx88

I did indeed replace the TPS and it didnt do anything . But I was working off an old tip from the buddy who owned it before me. He had it taken to a shop and they infact changed the TPS. So your saying the IAC valve is whats bad eh? And it has a full K&N on it with an Airaid TBS

98redf150

My truck used to do the same exact thing, I never found out the problem but I cleaned the filter and maf and it hasn't done it since and that was a year ago.

ghostrider

Iac valve fixed mine, you may just try removing and cleaning it. The tps will have nothing to do with the sound.