When I jumper my initial set plug my idle goes way down. Is that normal? Also, when jumpered, I don't seem to have too much control using the idle adjust on the plenum. What's up?????

 

Idle changes due to jumpering the initial set connector are normal.

How did you manage to get the idle down in the first place? last I remember you were having idle problems.

Jarrett

 

Yes, normal. Jumping the ISC tells the ECU to stop sending signal to the BAC valve, so when you make a change to idle, your BAC does not try to compensate for the change to keep it constant.

I never have much luck with the plenum screws. Just screw it all the way in, clean your TB, make sure you have a good working thermowax, and then set your idle with the secondary throttle plate stop screw and 8mm jamnut (may be covered with factory jbweld, but easy to chip out.)

Then check your timing, set your TPS, and pull out the ISC jumper. Idle should not change when you pull out the jumper.

 

scathcart, do you know of any pics I could reference to see which screw to adjust to change idle? curently my bac valve is compensating it up about 200rpm, which I think may be the cause of a mild stumble...
the factory manual doesn't talk about that adjustment, does it?? I assume not because you say it's possibly blocked up...

 

Question: If the ISC tells the ECU to stop using the BAC to compensate the idle condition, what would happen if I didn't have a BAC? Would I not need to use the ISC to make changes?

 

I was under the impression it stopped the ECU from making idle compensation. I wasnt aware it stopped the BAC cold.

 

Check the operation of the BAC when you jumper it.

You also need to jumper the ISC when you set the timing. It is a good idea to jumper the ISC even if you don't have a BAC.

 

Oh, I am not doubting you. Just didnt know that. Some good "gee whiz" info.

Jarrett

 

"Golly, now thar's somethin' you don't har ever' day!

 

Not quite sure what to say about that...