Idle is high
Thread Starter
Joined: May 2006
Posts: 3,974
Likes: 2
From: Spring Hill, FL
Idle is high I tried searching and searching and searching for a thread I had read about aftermarket throttle bodies and high idles. I can't find it again so here it goes.
Throttle body is a Summit 58mm. In the thread I saw it mentioned drilling a small hole, in the throttle body blades maybe? I don't know, I can't find it again.
Car will hold an idle just fine when it comes back down but usually it will idle up around 2k RPMs for an extended period of time before coming back down to the commanded idle. 5 seconds or so?
Here is a shot of the throttle body, I've currently got the water pump off the car so if I want to be pulling this thing to drill some holes, now is the time.
Throttle body is a Summit 58mm. In the thread I saw it mentioned drilling a small hole, in the throttle body blades maybe? I don't know, I can't find it again.
Car will hold an idle just fine when it comes back down but usually it will idle up around 2k RPMs for an extended period of time before coming back down to the commanded idle. 5 seconds or so?
Here is a shot of the throttle body, I've currently got the water pump off the car so if I want to be pulling this thing to drill some holes, now is the time.
TECH Veteran
Joined: Apr 2008
Posts: 4,985
Likes: 112
^^^^
OP, typically aftermarket TB's result in low idle/stall. Unless the stop screw has been messed with.
first confirm you have no vacuum leaks. more common source of high idle
did you push/compress the IAC valve when you swapped it over to the larger TB?? (you killed it if you did)
get a scan tool and read your IAC counts at idle, fully warmed up. They should be 30-35 (32). You can check TPS volts with a DVM or scan tool. They should be .67VDC closed and 4.5 vdc full open. you can adjust the TB stop screw to adjust the TPS vdc should it be off
about drilling the TB....that hole is drilled in the lower center of the TB between blades (where it is on your stock TB....BUT DO NOT BLINDLY DRILL A HOLE UNTIL YOU SCAN FOR WTF YOUR IAC COUNTS ARE. But again that is done to resolve low idle/stalling where the IAC is maxed out to 160ish counts and can't open any more
OP, typically aftermarket TB's result in low idle/stall. Unless the stop screw has been messed with.
first confirm you have no vacuum leaks. more common source of high idle
did you push/compress the IAC valve when you swapped it over to the larger TB?? (you killed it if you did)
get a scan tool and read your IAC counts at idle, fully warmed up. They should be 30-35 (32). You can check TPS volts with a DVM or scan tool. They should be .67VDC closed and 4.5 vdc full open. you can adjust the TB stop screw to adjust the TPS vdc should it be off
about drilling the TB....that hole is drilled in the lower center of the TB between blades (where it is on your stock TB....BUT DO NOT BLINDLY DRILL A HOLE UNTIL YOU SCAN FOR WTF YOUR IAC COUNTS ARE. But again that is done to resolve low idle/stalling where the IAC is maxed out to 160ish counts and can't open any more
On The Tree
Joined: Mar 2006
Posts: 122
Likes: 10
My BBK 58 used to cause high idle once in a while after driving it and it was because it wasn't always closing back down all the way when I let off the gas. I ended up putting a second spring on it, which is a good idea anyway, and it hasn't had the high idle problem ever again. Not saying that is your problem, but it is an easy thing to try.
Thread Starter
Joined: May 2006
Posts: 3,974
Likes: 2
From: Spring Hill, FL
Thanks everyone, when I put the car back together I'll hook up EFI Live and go do some datalogging. Then I will report back with some figures. Have a good Thanksgiving!
what i found with mine was there was no port for the iac to feed air when the blades were closed which would cause the engine to stumble and sometimes stall when the pcm had been reset. it woould act this way until the pcm learned to compensate. after drilling the port that stock tb's have, idle quality was good.
