I cleaned up a TB and installed new gaskets. The aluminum screws the mount the TPS were locked up and broke when I removed them. I had to step up the holes in the TB to 10/32 and I used cad plated steel aircraft screw to mount the TPS. I got thinking maybe there is a reason why GM used aluminum screws to mount the TPS. My question is, could the steel screw affect the TPS readings? I have not installed it since I did the work to it. Thx. in advance.

 

The TPS works like a variable linear reostat. Divides voltage by sweeping a contact across a linear resistive surface. Similar to volume controls on radios, only made from longer lasting materials. The only way for screw to affect the TPS is by being miss adjusted. .54 volts at closed and 4.5 volts or greater at WOT.

 

Just wondering why GM would use more expensive aluminum screws then cheaper steel screws. They seem to use the cheaper parts everywhere else.

 

Man, you aren't the only one puzzled by that! It was a pretty retarded idea to use those weak azz aluminum screws. I snapped both of them off on my TBI car a few years ago. I ended up paying a machine shop about $50 to get them out since they were broke off flush, and I didn't want to risk screwing up the holes. The crazy part was the machinist told me the original threads were French Metric. I've never heard of such a thing. Whether that was true or not, he said he'd have to special order new bolts and an expensive, special-order tap if I wanted to keep the same thread size. I said the hell with that, went to the local bolt and nut supply, and bought 2, 10/32 stainless steel, allen headed screws, a couple of lockwashers, and a 10/32 tap for like 5 bucks. I tapped the holes out and put in the ss screws, and it's worked perfect ever since. So to answer your question, I don't think there's really any particular reason for them using aluminum screws. Knowing GM, they probably did it so you'd end up breaking them if you attempt to mess with the TPS.

 

I'm a underpaid aircraft sheetmetal mechanic so drilling those out is just 2nd nature for me. I do think that GM does somethings on purpose so its good enough to make it thru warranty time lines and then rack you over the coals for replacement parts or repairs. Pat, the steel screw didn't have any effect on the TPS?

 

Yeah, it didn't seem to affect the readings. I've checked the voltage a couple of times with a digital meter since I used the steel screws, and everything appeared to be normal.

 

Thx. Pat for your time and input.

 

On aircraft they use aluminum, stainless steel screws or titanium (non-magnetic) when they are near sensitive avionics equipment. Thats what made me think about the TPS aluminum screws and all the other screws are steel in the TB.