Adjusting throttle position sensor

[nicktheviking]

I'm following Brad Artigue's throttle position sensor adjustment instructions and he doesn't specify whether to have the car on or off. I'd assume off, as the throttle position circuit is supposed to be closed?

[rlux4]

I'm going to suggest the off position, mainly because on our FI cars you'd be taking a chance if you work on anything electrical without first disconnecting the battery. There is constant 12V (unfused),going to the dual relay, and a spike can go through the battery and potentially fry it. I had a mechanic do it to mine. That's when I decided to educate myself in Bosch L-Jetronic Fuel Injection 101! Unless your trying to get a set point on the closed position by listening for the fuel pump to come on, then it would have to be on, just use caution.
Ron

[So Cal Mark]

the tps on a Spider doesn't control the fuel pump. You can adjust it with the engine off, since you're listening for the audible click as the switch opens and closes

[rlux4]

My bad! I read TPS and thunk AFM.
Ron

[bradartigue]

Engine off for testing OHMs on the FI components. It might not matter but why work on a hot engine when don't have to? You also don't want to risk an arc in that low voltage FI stuff.

[So Cal Mark]

having the key on or engine on to adjust the tps wouldn't be any different from driving the car and depressing the throttle. The old L-j system doesn't use a 5v reference like current FI systems. It's easier to hear the tps click with the engine off though

[launieg]

My caution is that the two mounting/adjustment screws can be easily snapped, especially if they are tight and haven't been removed in a while. Be forewarned! The trouble with metal screws in an aluminum throttle body I guess.

[nicktheviking]

Thanks to Brad, I now have a smooth idle! Wahoo.

[kristoj]

My caution is that the two mounting/adjustment screws can be easily snapped, especially if they are tight and haven't been removed in a while. Be forewarned! The trouble with metal screws in an aluminum throttle body I guess.

Both of my screws broke. Luckily the aluminum housing is easy to drill out and retap.