75 mm bbk T bodys

Thunder Flee

Registered User
Has anyone on here had any Idle problems from the 75 mm Throttle body's from BBK/ Edelbrock? I have tried everything from relearning the idle to changing Idle air motors and checking for vacuum leaks and it stilll has a high idle. When I first start it up it Idles great and whether it is warm or cold as soon as I hit the gas or put it into gear to go down the road it sticks at 1900 rpms. It even stays at 1900 in neutral rolling down the road. But when I come to a stop after about 15 seconds or so it drops back down to normal. Wierd Huh? I would appreciate any suggestions. Thanks PJ
 
It sounds like the IAC (Idle Air Control) valve is sticking. It's the valve that's mounted horizontaly on the throttle body.

David
 
Hey P J, glad to see you got the throttle body on. It's Jerry from Shockwave. You need to check the TPS sensor to see what the voltage is at closed throttle. I have the emission/diagnosis book in front of me and it says it should be .8 volts. That is 8/10ths of a volt. The computer expects .9-1.0 volts to be around 1500 rpm according to the chart. So too much voltage at idle may give the EEC problems.

I have heard that some people have to tweak the position of the TPS sensor on these BBK TBs to work right. You might have to slot the holes on the TPS sensor to give you some adjustment.

You need the throttle plate closed, but not so tight that you get binding. I would think that if you have the TPS voltage within range and then a idle of around 550-600 with IAC unplugged, that should be perfect. The car should idle below 700-800 rpm with IAC unplugged or the IAC wont be able to fully contro the idle.

If you want to look at my Emission/Diagnosis book let me know and I'll bring it to Shockwave with me and you can drop by. I have done the voltage check on my TPS if you want me to help you.

I still haven't got to look at your car since all the new mods.

Jerry
 
It could also be a sticking IAC valve, like David Neibert said. You can try cleaning it out with brake parts cleaner. When mine went bad on my old Cougar it started to idle at 3000 rpms. The diaphram was cracked inside, these things get real brittle over time. Don't touch the inside plastic diaphram as it will most likely crack. Just flush it out with Brake parts cleaner while it's off the car. If you think it may be bad you'll just have to buy Ford one. Aftermarket like Wells wont mount up on a SC. Although I have seen these metal style IACs work on a N/A 3.8 V6 with a wiring extension.
 
I found it !

I was looking at the stocker and the BBK side by side and looked at it some more and I noticed that the throttle plate on the BBK was on backwards. The shaft it bolts on to was turned around backwards and this caused it to idle way high. I guess the guy I bought it off of online messed around with it and probaly had the same problem. I put all back together right and problem solved. Thanks for the input though guys. Dave when are we all going to get together again. Tell Kurt I did not mean to invite myself, I just got a little excited like we all do. Hey Jerry I got the exhaust on and stopped by Shockwave tonight but you weren't there. Vic was and he likes! I'll stop by again tomorrow eve. PJ
 
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