[Novanutcase]

I''ve noticed that there are a lot of guys that have done the Aftermarket TB/Plenum swap and are having problems with hanging idle/low idle issues!

I just got done installing a Trickflow Plenum/75mm TB swap and am having the same issues. I''ve been doing some investigating and have a few questions/observations for you pros that may help others also.

1. I installed a new TPS on the TB so I don''t think I have any issues with the TPS itself although I''m not sure if there is a specific position that the TB blade guide to TPS needs to be in other than closed and you just put the TPS on as is? I assumed that the ECU will self position so there was no need to install it in any particular position.

2. I took off the IAC and cleaned out all the gunk with some WD-40 but am still having the same issues. At this point, I''m going to bite the bullet and just buy a new one and see if that fixes the problem.

3. I have heard that many of the aftermarket TB manufacturers sometimes get TB''s with the TB blade off round. In turn, when you open and close the blade sometimes it may hang on the ID of the TB and stay slightly open which may be causing part of the hanging idle. Have any of you heard of this? I am also suspect of this issues since a friend of mine that installed a Trickflow plenum/Accufab 75mm TB had the same problem and said he had wrestled with it for a few weeks and couldn''t get it to work. He finally gave up and just drove it that way and said that after a couple hundred miles it jsut fixed itself! Do you think that maybe the blade was out of round and that after a couple hundred miles it just self seated?
In my case, in the morning when the car is not to operating temp yet, the hanging idle problem is not as pronounced as when the car gets to op temp(the hang isn''t as long when it''s cold). Do you think that the off round blade issue gets worse as the TB heats up and the metal expands making the blade against the ID of the TB hang problem worse and therefore hang longer?

Sorry if some of this seems completely off but I''m trying to make heads or tails of this problem since, as I stated earlier, it seems like a lot of guys and gals are running into this problem! I''ve already gotten other offerings of solutions to the problem but I''ve tried most of them and they haven''t worked. When my friend told me about his experience it seemed to make sense with what I was told about the out of round TB blades!


John

[~C~]

Check this out. You may want to do this. I had a similar problem but the hang is the same as it was when I had my stock IP on. Looking this thread and scroll down to "How To: IAC Rev Mod (Fixing hanging RPMS)"

[Novanutcase]

Thanks for the reply! I saw that before but thought that if the problem was airflow through the IAC why would the hang be less when the engine is cold and more when it reaches op temp? That 's not to say that it isn't the solution so that is on my list of things to do.

John

[MATT02GT]

Have you checked the gasket area for leaks? Or tried to adjust the throttle screw?

[~C~]

I dont think the hang would be caused by the throttle stop screw though do you? I didnt do the hang mod because I didnt think my hang was enough to warrant it. It didnt really change to much from the stock plenum, so i didnt bother. Unless it starts bothering me badly, I will do it. Just a dumb idea, but make sure everything is nice and clean and smooth in there. you can spray the cables to make sure it isnt in the cable.

[sjr56]

Just installed new TB/Plenum and my idle would hang over 1200rpm. Tried disconnecting battery to reset memory and it did nothing. I thought the computer controls idle speed not the screw. Anyway it turned out the stock throttle cable bracket needed slightly bent to allow the throttle blade to close(guess the mounting holes were slightly further away).

Great link to the IAC mod. I had already fabbed an aluminum restrictor/spacer for my IAC. The mod helped with quicker rev downs.

[~C~]

Originally Posted by sjr56 Just installed new TB/Plenum and my idle would hang over 1200rpm. Tried disconnecting battery to reset memory and it did nothing. I thought the computer controls idle speed not the screw. Anyway it turned out the stock throttle cable bracket needed slightly bent to allow the throttle blade to close(guess the mounting holes were slightly further away). Great link to the IAC mod. I had already fabbed an aluminum restrictor/spacer for my IAC. The mod helped with quicker rev downs.

So you bent it out a bit? I may have to look at this just to see. It may be the manufacturer each of us went with.

[MATT02GT]

Pull of the intake pipe and see if the throttle blade is closing all the way. If its not, check the cable to make sure its not pulling on it somehow and check the trhottle screw...maybe its screwed too far in causing the blade to stay open

[sjr56]

I was under the hood reving and it would hang. I popped the cable off and it would drop. Didn't take much tweeking at all, just enough to get freeplay.

+1 on checking the throttle screw.

[~C~]

Well of course if the throttle screw is in to far then yea it will hang....however, usually they are set from the manufacturer to the correct setting. You need to look inside like matt said. Also, check to make sure your cable isnt catching on something. mine was at first and i rerouted it to make sure it was free.

[Novanutcase]

Checked throttle cable - free play all the way through
Changed IAC - Same shit!

Any suggestions?

John

[Novanutcase]

*****UPDATE*****

I was checking all the fittings to make sure I didn't have any leaks and I found the lower screw on the IAC was loose and it wouldn't tighten anymore. I pulled the plenum off to give it a thorough inspection and found that when Trickflow had machined the threading into that bolt hole it wasn't done right and the threading was all screwed up. It looked fine by just looking at it but when you put the supplied screw in the hole it wiggled around like it was too small. I checked the screw against the top IAC screw and they are identical so it wasn't a wrong screw that was provided me in the kit.
I sent the plenum back to Trickflow and they are swapping out another plenum for me.

NOW.......I put the stock plenum back on with the 75mm TB since it would take them a week to get me the new plenum. I had left the battery disconnected for a couple days as I didn't have time to get to the car before I installed the stock plenum. I started the car with the IAC plug off and the car started fine but idled at around 1100 - 1500 rpms. I let it idle without touching the gas for around 1/2 an hour and it settled around 1100 rpms. I plugged the IAC cable back in and there was no difference in idle. I drove the car the first day and it idled around 1100 - 1300 rpms and would hang at around 2000 rpms at decel. I figured I could live with it until I got the new plenum and after I installed it I would get a custom tune done to take care of the idle issue. The second day I drove it the idle dropped to around 700 - 900 rpms and it hangs for a second at around 1100 rpms but it's barely noticeable. I guess it takes the computer a few days to relearn depending on how much you drive. I expect the hang to eventually go away as the computer keeps learning but if it doesn't I may get a hand tuner and try and tune it out. Probably running a little lean with the LT's.

John

[Trick Tuners]

If your idle is too high this is because the TB is open too much and letting too much air in. I bet if you dataloged the IAC, it would be closed all the way. If you have the hanging idle, back out the set screw on the TB blade. If its backed out all the way and you still have a high/ hanging idle, this is due to a POS TB leaking too much air around the blade.