I have a b16 with a type r intake manifold. Whenever I unplug the ECU or a check engine light comes on the car will start to idle rough usually between 700-1400 rpms. The check engine light only comes on when I drive the car hard. I noticed today when i was sitting in my garage with the car fully warmed up the VAFC showed the throttle position was between .05 and .08% the pedal was completely disengaged and it was still idling rough. I did some searching and some people have said that this might either be a Intake Air Control or a Fast idle thermo valve
These are both located on the throttle body i believe. Can someone please tell me if they ever had this kind of problem and how they got it resolved. I hate just sitting there and the engine reving all on its own
Thanks

 

It sounds like a vaccum leak or possibly a bad IAC. Take your air intake away from your throttle body and block the hole insode of the throttle body with you finger and see if that fixes it. If it does, this indicates a bad IAC, you can either look for a new one, or take off the IAC and make a gasket that will cover the holes between it and the throttle body and bolt it on, and your problem should be gone. If this does not fix it, you probably have a vaccum leak or a bad gasket between the intake manifold and throttle body, or the intake and the head.

 

Anyone Else have any ideas or suggestions??

 

So heres what happened I took of the intake and plugged the hole in the throttle body up with my thumb. NOTHING. The car still kept on idling hard, so i kept on looking and i notices a hissing sound, i thought it was just the intake manifold taking in the air so i put the intake back on and it was still hissing. I narrowed downt the sound to right by the MAP sensor and the connection between the throttle body and the intake manifold. I blocked other sounds of with my hands and it was directly coming from this area. I dont think it is the map sensor. Is there supposed to be somekind of gasket or anything between the map sensor and the throttle body. Is there supposed to be any kind of vacumm sound coming from these parts of the engine if there isnt well then i think its the gasten between the throttle body and the intake manifold. If anyone has had this kind of experience in the past i would greatly appreciate some help.

 

get some carb cleaner
and spray it on the TB gasket (where the TB and IM meet)
if it changes the idle you found your leak.


[Modified by Kamin, 7:52 PM 2/12/2003]

 

I showed my problem to some of my friends and they also said its a vacuum leak but we couldnt tell exactly where it was coming from. So after looking at it for like 10 min we noticed that there was a screw missing from the throttle body and thats where the hissing noise was coming from. I have a 95 LS throttle body and its missing that one screw. I couldnt find an exact picture of the throttle body but i found a similar one from a GSR its almost identical but mine is missing the gold screw that is at the top of the throttle body next to the MAP sensor. Could someone tell me what this screw does? I have to get a new one from the dealer as soon as they open in the morning. I hope this solves my problems Thanks.

 

Anyone??

 

That gold screw? thats your idle adjusting screw

 

What code is stored?

 

I brought it to the mechanic and they said that the check engine light has to be on all the time. I shut the car off and turn it back on and the light is off. I ordered the screw it was 6$ I hope it solved my problem.

 

The check engine light shouldn't be on all the time. Knowing what code is stored will narrow down your problem. Or you can poke and hope and keep throwing parts at it.

 

all i can say is that screw is VERY IMPORTANT...