Just installed the fast 90/90. I got the TB off a guy second hand and he said it stuck slightly on return. I ran it last night and had some pretty bad idle issues. Stuck at around 3K when off the gas. Today I grabbed a return spring and installed it on the car. Upon firing the engine up, it stammered and the shot to 4K, hung there for a sec and dropped to about 2K. Killed the car, checked all my sensors and visible stuff and noticed the TPS wasnt plugged up from some fooling around after I drove last night. Plugged it up and started the car again. Shot straight to about 5K. Didnt know how high it would end up going so I killed the engine. Went back into the bay and looked to make sure every vacume line is hooked up, was fine as far as I could see. Checked the intake bolts to make sure nothing was loose or out of wack. Found 2 bolts that seemed to have backed out a tad, tightened them and started the car again. Car acted funny and I gave it a bit of gas and it shot up to 4k and then dropped alittle. Killed it again, removed the TPS to make sure it wasnt screwed and reinstalled. Started the car, let is shoot up and drop to about a 2K idle, then unplugged the TPS sensor, idle dropped to 700 or so and didnt shoot back up. Drove the car around the block like that and it hung some, but not horrible. Pulled over, plugged the TPS back in, and it went ******* crazy. Had to pull back over and unplug. Now I am sorry this post is so long, but WTF. I cant find a vacume leak, mechanically it doesnt make sense, and dont know what to do next. When I put the two shells of the intake back together I made sure the seals where straight as they came. Ideas?

Brandon

 

Ideas?

 

Severely out of whats IAC effective area table? Did you try unplugging the IAC motor?

 

Nope, I was kinda short on time last night. I am going to go ahead and get a new TPS today and fiddle with it some more tonight. I just doesnt make sense.

Brandon

 

I think the IAC might have more to do with the strange RPM increases and decreases than the TPS, but then again you said it improved while unplugged. Cant hurt to try.

 

It's probably the TB itself. I tried fixing my FAST 90mm TB to no avail (you probably have an early batch unit- they stuck like crazy). I ended up getting a TPIS 90mm TB and the car ran fine.
FAST did tell me to send it in for repair, so at least they were willing to fix it. Give them a call.

 

externa engine and pcm sections might get you more responses.

Before you go and throw a bunch of money at it, i would verify your tune is set up correctly to handle the larger TB (IAC Effective Area Table), and veryify that you are not having a mechanical issue.

IIRC, if the TPS or IAC sensors were faulty I belive you would be getting an SES light.

 

I do have an ses light, but havent pulled the code yet. Talked to TSP about the retune and he said to make sure the IAC is sealing right. Apparently the O-ring seldom fits right. That would make sense from the symptoms.

Brandon

 

there have been many threads on this...do a search..

mine was a 90mm TPIS shaft problem...
https://ls1tech.com/forums/showthrea...cking+throttle

 

Let us know what the codes are when you get it scanned. Autozone will do it for free.