"Surges when idling after it warms up".....

[jerometene]

Hey guys, I've got a 92 LX (Trickflow stage 1, redone heads, and 255 fuel pump) that when it warms up, it surges when it idles. The rpm goes up and down and I don't why. ...Oh yeah, I have a MSD box (BTM unit) I installed on it also. I know its for a supercharger and thats what I brought it for but decided to wait til I could afford better heads.

Thanks guys

 

[HISSIN50]

Welcome to the boards!

Any codes?

Is this a new issue or has it done it since the last batch of mods?

Where is your idle set?

 

[jerometene]

It set for about 6 months but no, it didn't do it before. I think my idle might be set too low but would that do it?... Could it be my MSD?

"Thanks for your help guy"

 

[HISSIN50]

Since it sat, I'd look for a vac leak.

A low idle setting could do it. If it's a ways above or below the commanded idle, the EEC can get confused.

You could try setting it at about 800 RPM hot (no load) idle with the IAC disconnected. When you plug the IAC back in, the duty cycle will be low or nill.

If you do this, be sure to put a reference notch on the idle screw and record your adjustments so you can always get back to where you started.

Good luck.

 

[7upstang91]

Hey guys, I've got a 92 LX (Trickflow stage 1, redone heads, and 255 fuel pump) that when it warms up, it surges when it idles. The rpm goes up and down and I don't why. ...Oh yeah, I have a MSD box (BTM unit) I installed on it also. I know its for a supercharger and thats what I brought it for but decided to wait til I could afford better heads.

Thanks guys

Check the codes, as stated. Then pull a couple spark plugs to see how they look.