Yesterday and today, I installed the FAST manifold and a Nick Williams 90 throttle body. Everything went pretty smooth. Cut the **** out of my arms though. What was GM thinking when they put those clips in the cowl? Anyway, started the car and the idle just went from 2000 to 3000. Drove the car to the gas station to get gas and it's idleing still at 3000 to 3500. Come to a stop and it stays there. So I come home and adjust the idle screw all the way out, no change. I pull the throttle wire off and the throttle closes another, oh, 1/4". So I start adjusting the bracket holding the throttle cable. I finally get it to where if your going down the road and push in on the clutch, it idles at 2000, come to a dead stop and it drops to 1000 to 1100. So,I got to thinking if it could be a vacum leak and the only place where I can think a vacum leak could be would be on the map sensor in the back of the manifold. Everything else is on there the way it's supposed to be. The reason I say the map sensor is it just sticks in a hole back there kinda flopping around in the hole. Is this supposed to be this way? That's the way it was on the old manifold also. Could this be the problem or is there something else I need to be looking for?

Oh and I forgot to add, I pulled all of the air crap off also. I do have the SES light on right now, I just haven't had time to look at the codes, but I assume that is due to the air not being attached. I'm going to have the car tuned, hopefully this week or next week so if it is the air codes, they can do away with those codes, right? But this wouldn't have anything to do with this high idle issue would it?

 

The AIR wouldn't affect the idle. I thought the idle was PCM controlled though? What screw were you adjusting? It might be all fudged up due to the larger throttle body, the intake shouldn't have anything to do with it. I just chimed in to let you know AIR won't do it.

 

On the front of the NW throttle body is an idle set screw, right now it's not even touching I've got it turned out so far. As for the air, I didn't know what could be screwed up. I didn't think the air would have any effect but I thought I would give all the facts so as to get some advise.
THanks

 

I just went out and got the codes that are causing the SES light,

PO121 Throttle Position Sensor Performance
PO410 Air System
PO412 Air Solenoid Relay Control Circuit.

I expected the PO410 and PO412, but what causes the PO121?

 

Anyone help me out on this?

 

Did you install the o-ring around the IAC motor on the new TB? Either that or you have a vacuum leak somewhere. I have heard of people leaving the washers stuck to the bottom of the intake after removing the bolts that FAST ships them with. They sometimes stick to the bottom after you remove the bolts to install the intake.

Or you have the throttle cable in the wrong hole. What year is your car and what hole are you using?

Check you PM's

Nick

 

Nick, yes the o-ring is installed on the IAC motor, I checked and all washers that came off the bolts that came on the manifold from FAST are accounted for. I have a 2001 SS and really the throttle cable will only fit one way as there is a round tab that fits in a hold to prevent it from coming out of the bracket. The absolutely only thing I can think of is that MAP sensor. Although it is in the hole it's not very tight and I can see a vacum leak there. I've checked the little vacum line on the passenger side and the brake canister vacum line and they are both on there. Even the MAP sensor is in the hole. How would I check along the plane where the manifold sits on the heads and the block to tell if there is possibly a vacum leak there. Like I said in my first post, I turned the set screw to where it is not even touching. THe car now drives and I don't even have to touch the gas, it will go along at 2000 rpm, push in on the clutch and it will jump to 2300 rpm. Come to a dead stop, and not one second before, and it will drop to 1100 rpm. Thanks for your help.

Bill Estes

 

What TPS % does your car read when the TB is closed. Make sure you do not need to reset the TPS position.

 

I think that his throttle cable needed to be adjusted. It was holding it open a little.

Nick

 

Nick, I think you were right, I did adjust the cable and it did bring the idle down. However, still when your going down the road and you push in on the clutch, you begin idleing at 2000 rpm it will come down to about 1800 rpm until you come to a dead stop and then it drops to 1000 rpm. It did this ever since I put the cam in the car. Its just agravating as hell that when you let off the gas your idle won't drop to where it's suppose to be. I've seen a lot of this on this board and nobody seems to be able to fix it, at least not from what I've seen.

 

How do you reset the TPS position?

 

I am having the EXACT same problem, although I have the FAST 90mm TB. I can't figure it out either. Maybe we can work this out together. It's so embarassing to come to a light looking like John Force.

 

Boy do I know how that feels. Do you think Nick could chime in on this? Or really anybody.

 

If you have some form of tuning software, have you checked the Idle Air in Gear?

 

Does it make a difference that I have a 6 speed?

 

Yes, you still have Idle Air tables

 

E-mail me a copy of your tune. nickw_61@yahoo.com.

Do you have a scan tool?

 

Are the tps screws adjustable? turning tps may adjust parameters that pcm sees tps is at. A vacuum leak would make to car run horrible, lack of acceleration and bad idle.
also you would hear to vacuum leak. Also check throttle cable binding.

 

Nick, I just have autotap. I presume your thinking I something like LS1 edit or HP tuners, right. No I don't have either of those. Thought about getting one or the other, just haven't done it yet. I was taking the car over to Kirk at AP Engineering before all that happened. I will say this, the car runs great when driving it, but when driving tonight with my wife in the car, going through 25 mph speed zones or 35 mph speed zones, the car is is idleing at 2000 rpm and 45 mph. not good. Push in on the clutch jumps to 2500 rpm, once it jumped to 3000 rpm. Now also I noticed something else, she had the a/c on when it was doing that. Turn the a/c off and it's back to where it was, 2000 rpm idle, push in on clutch drops to about 1800 until a dead stop then 1000-1100 rpm. All you have to do is touch the gas and the rpms jump to 2000 until it realizes "hey, I'm not moving" and then drops down to 1000-1100. Biggest problem is trying to maintain the 25-35 mph speed limit with the car idling at 2000 and wanting to go 45 mph. Let me know what else I could get you to diagnose this problem.

Bill

 

I don't think the tps screws are adjustable. I don't think there is a vacum leak, and actually, the car runs good, doesn't really have a bad idle (when it does idle) except when your driving and the speed limit is 25 or 35 mph and the car with no foot on the gas is going 45 mph.