Im having trouble with my ls1. I installed a ported fast 90/90 (tb). Ever since I installed it, its been idleing high and when I press in the clutch it revs up then idle takes forever to drop (im thinking the throttle is getting stuck open but ive already check throttle cable , check for leaks around tb, and made sure intake bolts were tight. I have no clue at this point what it is. Another thing also im getting a p327 code "saying knock sensor bank 1". I already replace the rear sensor Im not sure which one that one was but it was the one towards the fire wall and also replaced the harness. So im stuck.. Any knowledgable ls1 expert help please..

 

search "hanging idle"
Also, what TB did you install with the intake? I had the same problem when I had a FAST TB, so I switched to a Nick Williams, and the problem went away. I'm guessing it could be your TB blade isn't adjusted to let enough air through for the IAC at idle. You can either drill a hole in it, or attempt to adjust the blade. IMHO, it is WAY easier to just drill the damn hole in the blade. Just my $.02 though

 

the map sensor in back could be loose and causing a vacuum leak.I glued my map sensor in with silicone.

 

Vacuum leak, misadjusted TB blade, tuning. Do not drill a hole in the blade. That is pretty much a bandaid and looked down upon. Tuning would help on a 90 install when your going from a 78mm to a 90mm the throttle scaling could prolly use some work.

 

I bought Tb from a guy on ls1tech i forget the brand just has initals on top of the tb. So Im going to look into the blade of the tb because its like if it is open because the car is acting like im giving it throttle..

 

Sounds like a vacuum leak to me. a trick that our techs used is to idle the car and spray brake clean in the area of the intake. that will screw with your idle if it starts pulling it in.

 

You just need a tune. I bought a ported ls6 intake and a ported and polished stock throttle body and I had the same issues.. I tried EVERYTHING. looked for leaks, put my AIR system back on, and finally some local guys said I needed to get it tuned and it would stop... I'm reluctant to admit, he was right

And don't drill into your throtte blade!

 

i'm leaning towards vacuum leak also . . . are you tuned yet for your intake?

 

The brake clean trick is easy and fast. After that I would look at getting a tune. You are getting alot more air in the engine now and the tables are not setup for it.

 

Well lol check this out... I looked at my old ported TB because I bought the car with it already on it and it already had a little hole in the blade of the tb (not the fast 90 tb). I was like so it probly had this problem before I had switch the intake out but it wasd hiding it all this time.. As far as tune goes well my car was tuned when it had stock 853 heads no crank pulley and on the ls6 setup. I changed it to the 241s posted in my sign also add a crank pulley and the ported fast 90/90.. You really think thats why the idle is crazy because it needs a tune or because vacume leak was their but previous owner didnt fix the problem???

 

Constantly searches for idle, when you throw it in neutral it hangs at around 2k rpms until you stop, give it a tiny rev and it hangs at around 1.5k for a few seconds.. that's what mine was doing and the tune took care of it.

 

You changed the valley pan bolts when you did the intake right? If not, the intake will not mount correctly and you could have possibly cracked the bottom of it when tightening the intake bolts. If you DID change the valley pan bolts, then it's safe to assume you can start hunting first for vacuum leaks and then if you've determined there are none... get it tuned. Any time you change air flow into the motor (camshaft, heads, intake) it's pretty much a necessity to get it tuned. Check the map sensor, check the tiny hose that connects to the back of the intake, double check the bolts, including the ones holding on the throttle body. Make sure the throttle body gasket is good. Did you use new rubber intake gaskets when you did the intake? If not, you made sure the ones you used were good, yes? Just trying to cover all the bases here. You can also try a TPS reset:

Unplug tps, turn key on (do not start motor) for 30 seconds.
turn key off, plug tps back in
turn key on (do not start motor) for 30 seconds.
turn key off.

This should set the tps % back to zero. If you adjust the throttle adjustment screw, be careful not to go too far or you'll set a code for too high of TPS voltage, and this will have an effect on wide open throttle tables, and all sorts of other **** in the tune. Remember after adjusting the screw, you have to do a tps reset, or the computer will not compensate for the change you made. That is a mechanical change, so if the tps % is 0 and you adjust the screw... it will effect that percentage as if you were pressing on the gas... thus confusing the computer. Hopefully that makes sense.

Lastly, I am BY NO MEANS an expert on this stuff, so if someone knows better than I... please correct me.

Keep us posted on what you find out. Good luck.

 

Thanks Brad Im going to try those things and If it dosnt work than ill retune but this time a dynotune. My brother kept telling me he thinks the blade is getting stuck but I dont see how?? I will keep you all posted to see If I can fix the problem..

 

With the engine off, it's easy to check if the blade is getting stuck... pull everything off of the front of the throtte body (MAF, bellow, lid, etc.) Or at least move the stuff so you can see the blade... then simply open and close the throttle to see if it's getting stuck somewhere. If you have a buddy that can help, have him or her sit in the driver seat and have them press on the gas... fully open and fully closed. See what the blade is doing while they're doing that. Ruling out the blade shouldn't take more than a few minutes. Keep us posted.

 

if its a Fast tb you can almost guarantee its hanging...mine did and it only did it when bolted on, take it off and it works perfect

I had to grind and sand carefully for about an hour to fix it

sounds like either that, your tune, or a vacuum leak caused by the knock sensor wiring holding up the intake

get some starting fluid or wd40 and spray around everything...intake, tb, hoses, map sensor, ect...brake cleaner will strip paint off anything it touches, starting fluid should not

DO NOT DRILL THE TB

someone drilled mine before I got it and I had to plug the hole with a bolt just to get the car to idle below 2k rpm

 

Well I found out TB blade is getting stuck open thats why my throttle is so high. Going to replace knock sensor also (bank1). What are some Idea to eliminate the problem with the tb blade getting stuck?

 

You were right.. Thanks

 

Damn glad to hear that you found out the problem. My car is doing the same thing, i should be changing lids here soon i'll have to check this out and see if mine is sticking.

 

if its a fast throttle body thats your problem had to take the blade off and clean up some spots wher it was rubbin

 

Its a 90 tb but not a fast. Ill upload a pic ...