yorkie

there is only 2 screws that hold it not 3 There are three that hold the opti the the engine???

turbo_Z

if you want a lower IAC count then what you could do is drill out the IAC bypass hole in the TB to about double its current size. by enlarging the IAC bypass, you have no loss in idle quality and the IAC motor doesnt need to work as hard to keep up with the air demand at idle. the bypass hole is already there so all you would be doing is modifying it like you have modified everything else in and on the motor. id also like to point out that 30-40 seems like a decent value but that is only on stock cars.. whos to say what is ideal for a heads/cam stroker car? and whats the downside to having counts in the 10s?.. nothing. btw this mod only applies to stock TBs though... i wouldnt drill into a $400 aftermarket unit.

yorkie

help, its a 383 so it is ingesting more air each stroke.

Mtrhds94Z

Opened it for inspection, found the 3 screws that hold the optical sensor mounting plate had SHEARED OFF.
besides a poor ground, it was all over the place and rubbing, etc.

See above...
The sensor 'mounting plate'[the whole black plastic plate with the plug part, etc] is held to the inside of the opti aluminum housing with 3 screws[not talking about the 2 sensor screws?]
All 3 were sheared and showed evidence of rust indicating it had been a while, or they were partially sheared for a while.. not fresh looking..
First time I ever heard of that..

yorkie

screws? It has 4 screws???? So 3 were sheared?

Mtrhds94Z

If you want I can send a pic?
It was the optical sensor MOUNTING plate....
the part that screws to the actual aluminum housing with 3! yes 3 screws... [it's the flat plastic part that also has the OPTI PLUG going to it, thru the housing]
then the sensor has 2 screws that goes onto that...
Then the tin EMF shield on that
Then the bakolite 'seperater']
Then the rotor
Then the cap

Have you ever disassembled an early[93-4] opti?

yorkie

ttt

Mtrhds94Z

Dist cap has 4 screws for both.
Once again the PLASTIC PLATE inside the opti has 3 and they all sheared..

yorkie

sensor has two, cap has four, bearing piece has 2 rotor has 2??

Blk94Z28LT1

drill out the idle passage hole like turbo said. It is originally 5/32. I drilled mine out to 7/32, made a big difference in idle with the hotcam. IAC counts before drilling 160 (max i think) after drilling 20-25 in park, 40-55 in drive.

Mtrhds94Z

[Right, and the plastic plate the sensor screws to with 2 screws has 3 that attach it to the housing.
Is your early or late? Late may differ [I never opened one.]

yorkie

ttt

Dan K

First off 35mph in 4th gear with an A4! What kind of rpms is that at? No wonder it's studdering. Could it be that when the converter locks in 4th gear at 35mph the engine rpm is so low that the car starts to chug/studder? Then when you slowly apply the gas you reach the TPS value that unlocks the converter and the studder goes away?

Have you drilled the hole in the tb as others have suggested?

I was just tuning a car with a stock bottom end and a 236/242 cam and in park at idle I got the IAC counts to around 30-32 and the in gear idle counts to around 60. Are you sure the IAC is still good? Have you tried a new/different one?

Have you tried opening the throttle blades even more to get the park IAC counts lower so that the in gear IAC counts drop also? Bigger cams may need the tb blades open farther to get more air in.

People are giving you ideas, but we don't know if you're trying them and what they're doing or what. Help us and we'll help you.

yorkie

I will post what the outcome is, been busy.

Dan K

Before you go drilling anything...
Are you sure that IAC you have on the car is still good? I could turn the minimum air gap screw all I wanted and my IAC counts wouldn't change. New IAC fixed that real quick.

I would hold of on the drilling until the other things I mentioned are not helping...