I bought an Accufab upper intake plenum along with a 75mm throttle body. I connect everything like the stock peice, but now the rpms hover at about 2500rpm for about 5 secs then drop to normal about 750rpm. What could do causing this problem, has it happened to anyone else before.

There was an inlet on the Accufab unit that was much smaller so I thought that was the reason. Mabye they gave me one for a 99 because they have a smaller vaccum line. So I drilled it out and put the stock tube in and now the rpms hover a little higher and longer... Help!!!!

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This is a very common problem with the swap of plenums. Disconnect the battery over night and let it reset. It may take a couple weeks to fix itself. This happened to me when I installed a larger TB. Trust me, it will go away.

 

Thanks for the advice, I have the negative cable disconected. I am going to let it sit like that all night and see what happens in the morning... I hope it works!!

 

It wont happen over night. You have to let it get used to the extra air its taking in. SO it may take up to a wek or two.

 

Why is it that some people experience this problem and others don't? It very frustrating. I can't figure out whats causing it, and what a couple weeks will do. I would think that the computer would respond no problem to this simple bolt on... But I guessed wrong.

 

had the same issue with my 2002 GT.... lasted two days, the second day i turned it on and off like 5 times then let it sit in idle for like ten minutes and walked away and it never did it again....who knows

 

dont think i ever had that prob when i installed mine. let us kno how u like the performance gains. i installed mine with my s/cer so i have no idea how it performs alone.

 

I did notice a difference in power. But Since I drilled out that whole to the bigger size, my rpms at idle are 1200rpm... So it was like that for a reason. F*ck... Im just not going to use it, and put the stock upper plenum on. I tryed letting it idle for like half an hour, I now have a check engine light on. But disconnecting the battery will fix that. Thanks for your help though guys..

 

dont chuck it bc of a check engine light. see how i goes for a few weeks then decide.

 

I had this same problem, and it went away after a week or so. When I rebuilt my motor is started doing it again, what I did that time was tighten the throttle spring, which fixed it.