Should I replace the FULL THROTTLE switch?

[Warren N.CA]

1990 325is. During trouble shooting the bad idle, discovered that the full throttle switch has a resistance of 25 to 100 Ohms when closed. It should be close to zero Ohms (The idle switch is close to zero.). 100 Ohms is surely a lot less than infinity (open switch), but I don't know if it is low enough for the DME to reliably interpret it and provide the appropriate mixture enrichment. I can't notice any obvious problems under full throttle operation. It seems fast and smooth, with no stumbling upon acceleration.

Should I change this switch?

[winfred]

it won't hurt the running being bad but if it works it may help power

[Bellicose Right Winger]

Reomve off the cover and clean the contacts w/ 320 grit emery cloth.

Paul Shovestul



1990 325is. During trouble shooting the bad idle, discovered that the full throttle switch has a resistance of 25 to 100 Ohms when closed. It should be close to zero Ohms (The idle switch is close to zero.). 100 Ohms is surely a lot less than infinity (open switch), but I don't know if it is low enough for the DME to reliably interpret it and provide the appropriate mixture enrichment. I can't notice any obvious problems under full throttle operation. It seems fast and smooth, with no stumbling upon acceleration.

Should I change this switch?

[Warren N.CA]

with sandpaper and the like. This will cause pitting, arcing, and failure within a short time. If I go to the trouble to take it apart, I will put in a new switch.


Reomve off the cover and clean the contacts w/ 320 grit emery cloth.

Paul Shovestul

[Bellicose Right Winger]

Never? Nonsense. As someone who has done this successfully on numerous occasions, I completely disagree. Furthermore, since it's likely your contacts HAVE already failed, you can't possibly make them any worse. Emery cloth and sand paper are completely different animals.

Paul Shovestul



with sandpaper and the like. This will cause pitting, arcing, and failure within a short time. If I go to the trouble to take it apart, I will put in a new switch.

[winfred]

it's usually just oil that's screwing with them on the tps wot switch

[Bill R.]

of mist from the crankcase and gets sucked into the manifold will settle out some and it ends up in the tps gumming up the works... frequently if you take it apart and clean it up with some contact cleaner it will work fine.. And since its a low amperage contact point they usually aren't burnt... And all electrical contact point manufacturers state not to file or sand their contact points for the reasons that Warren stated.. On large amp carrying contactors its the kiss of death but you can usually get away with it on something like these switches that don't carry any current.. and if i was in a bind i would file or sand them anyway just to get me out of the bind...such as a 115F day and my home ac compressor has kicked out on overload cause one set of contacts have arced out and its trying to run on one phase of power.... That said i wouldn't hesitate to clean them up with some emery cloth if the overall condition of the switch looked pretty good.







it's usually just oil that's screwing with them on the tps wot switch

[Jeff N.]

...and not fubaring the switch. When I opened up my old TPS for this picture, I don't think it would have been possible to put humpty-dumpty back together again. I recall the cover came off in several piece's even though I was trying to be careful as I pryed it apart.

http://home.comcast.net/~jsnord/pics/tps.jpg

[Warren N.CA]

of mist from the crankcase and gets sucked into the manifold will settle out some and it ends up in the tps gumming up the works... frequently if you take it apart and clean it up with some contact cleaner it will work fine.. And since its a low amperage contact point they usually aren't burnt... And all electrical contact point manufacturers state not to file or sand their contact points for the reasons that Warren stated.. On large amp carrying contactors its the kiss of death but you can usually get away with it on something like these switches that don't carry any current.. and if i was in a bind i would file or sand them anyway just to get me out of the bind...such as a 115F day and my home ac compressor has kicked out on overload cause one set of contacts have arced out and its trying to run on one phase of power.... That said i wouldn't hesitate to clean them up with some emery cloth if the overall condition of the switch looked pretty good.

[Bill R.]

...and not fubaring the switch. When I opened up my old TPS for this picture, I don't think it would have been possible to put humpty-dumpty back together again. I recall the cover came off in several piece's even though I was trying to be careful as I pryed it apart.

http://home.comcast.net/%7Ejsnord/pics/tps.jpg

[Warren N.CA]

Well if it's just oil, I'll try cleaning them.

[Jeff N.]

yabut...how do you get the cover off in the first place? I seem to recall mine came off in about 3 twisted pieces. Maybe this is the difference 'tween you pro's and us shadetrees? Or...maybe that Tuscon heat makes that plastic come apart nice and easy? :D

[Bill R.]

the plastic cover on the afm come off by itself here... and most of the plastic under hood is so brittle that you have no problem taking it apart...thats the price we pay for no rust... rubber moldings , weatherstripping , plastic and rubber suspension bushings seem to have a short life in the desert...
I would venture to guess that if i worked on cars that spent most of their time in seattle I'd have the same problem getting the cover off...although i have worked on my new next door neighbors 67 malibu convertible and the rubber on it doesn't look so good : ) and its from seattle...






yabut...how do you get the cover off in the first place? I seem to recall mine came off in about 3 twisted pieces. Maybe this is the difference 'tween you pro's and us shadetrees? Or...maybe that Tuscon heat makes that plastic come apart nice and easy? :D

[Warren N.CA]

model airplane glue.



the plastic cover on the afm come off by itself here... and most of the plastic under hood is so brittle that you have no problem taking it apart...thats the price we pay for no rust... rubber moldings , weatherstripping , plastic and rubber suspension bushings seem to have a short life in the desert...
I would venture to guess that if i worked on cars that spent most of their time in seattle I'd have the same problem getting the cover off...although i have worked on my new next door neighbors 67 malibu convertible and the rubber on it doesn't look so good : ) and its from seattle...

[winfred]

you can get it off with a knife, i had to change the polarity of the idle switch for a turbo 240 volvo project i did a few years back