So I bought a ported and polished throttle body a couple months ago. After I installed it I kept getting a high idle after the engine was warmed up and I put it in park or if I revved the engine in nuetral, the RPMs would come down and hang at 1200 rpm. I tried remounting it several times, but nothing cured the problem permanently.
I put the stock throttle body back on the truck, and the idle was back to normal 100% with no problems. I figure its the modified throttle body .... it must have a problem. I decide that I like a bigger TB, so I broke down and bought a Fastman.
I got the Fastman mounted and went to go take it for a ride, and same problem again. With the fastman, now the idle fluctuates a bit but wont come down until I shut it off and restart it once it the idle sticks. Both sensors have been replaced in the TB. I even swapped out the old TPS for the new one today to see if that fixed it ..... and it didnt.
I just dont understand whats going on now. I have tried doing a hard reset and a TPS sensor relearn. If I drive the truck short distances with normal driving (no driving like I stole it) nothing happens. The second I put it in park and rev the engine to see if the idle is fixed or not, the problem is back.
What do I do now? Just drive it and hope it relearns the extra air flow eventually? Is it even possible that a preexisting fault somewhere on the truck only is noticable with the bigger TB? This issue goes away compeltly with the stock TB. Im getting ready to sell the fastman and just forget about the bored out throttle body idea but I have already spent a lot of money trying to get this to work. Any ideas guys? If this truck was a horse, I would probably shoot it right now.

 

I could try it out on mine to see it it's specific to your truck....

 

Thanks for the comments guys. I actually sold the old modified TB to another member and am waiting to see if he has any problems with it.

I wish I had a smoke machine ..... then finding a vacuum leak would be a dream. I just dont understand how it never affects the truck with the factory throttle body.

 

You can test for vacuum leak with brake cleen, to see if the motor stumbles when it is introduced.

 

I tried spraying brakleen and using propane to find a leak, no luck. Im heading to the auto shop today to see if they have a smoke machine that they could test the truck with. I just hope its not a manifold gasket or something expensive.

 

Lol. I probably could do it myself. I called the shop and they said they would do a smoke test on it, but they are thinking its the throttle bodys air flow thats creating the problem. Im going to try and take some brakleen today and spray around the manifold to see if I can get anything. Otherwise I will drive it for 1000 miles and if it still does it, Ill take if off and try to sell it.