Throttle valve switch woes..., little to no idle... Options

[stateofidleness]

to precede.... i have an idle issue where the car either has VERY low idle (like 200, or 100) or no idle at all (tach won't even move). also, once i drive the car for a few minutes, whenever i have to go back into first, it just dies.. does not return to idle..

with that said, i've been directed to check the TPS or Throttle valve switch..

finally found the switch, and using the Pelican tech article ive gotten to the point where i connect common to common (middle prong) and positive to "idle" prong.

..and... shouldn't it give me a reading?? i have it set to audible (the ohm meter) and i hear nothing once the two connections are made.. i even tried either side of the common prong to make sure it was on the right one...

does this mean dead TPS? i know they're NLA and i don't really want to fork out the $$ to fix it as the car is for sale.. is there a way to keep my idle normal and still keep it drivable? dying at every stop sign or intersection takes all the fun out of 914 ownership as you can imagine..

[Rand]

The idle adjust (air bypass on throttle body) won't bring it up?

[stateofidleness]

no.. when i adjusted that idle adjustment screw, seemed to have no effect whatsoever...

[jesiv]

What year and engine?

[JeffBowlsby]

The TPS idle contacts are the two on one end, not the middle contact. Check the calibration diagram.

[stateofidleness]

'73 1.7L

the middle is ground, which i had correct
then i check the prong on BOTH sides of the middle and neither gave me a reading... one of the two was the idle prong and neither gave a reading so...

i went by the switch diagram on the pelican article.. is there a better one?

[Rand]

no.. when i adjusted that idle adjustment screw, seemed to have no effect whatsoever...

Something's fishy. That screw changes the airflow past the butterfly (if working properly) which MUST affect idle.

I don't know if this is your problem, but the fact that it does nothing certainly makes me wonder why.

[stateofidleness]

dumb question, but i should adjust the idle screw while the car is on right?

what i did was set the TPS in the "middle" and put it all back together.. then with the car idling (which was up at like 2k!) i adjusted the screw which seemed to help.. got it to around 1k 1100 range. the tach seems to "jump" around though... sometimes it'll flick up to like 1300 for a sec or dip below 1k..

not sure if this is related.. but if im at a stop sign, and go into 3rd by mistake, instead of 1st and try to take off.. the car dies.. wouldn't it just rev high instead of dying?

also, the hose that plugs directly into the U-shaped plastice intake tube seems pretty loose... has like a metal tapered end on it.. anyway to tighten that up?

[Rand]

Idle air bypass screw: Yes, adjust that while the car is running. It should immediately respond.

TPS: Perhaps you should disconnect it, drive it, and report the differences you experience.

Third vs First: Ok, are you serious? I'm going to risk the joke being on me by answering this. Maybe you just have your understanding of high vs low gear behavior backwards. High gears = high speed. Low gears = low speed. If you are at a stop and put the car in third by mistake (expecting first) then of course it will rather bog and die instead of rev high. If you are down-shifting and hit a lower gear than expected, it will rev high. If you are up-shifting and hit a higher gear than expected, it will bog. From a stop, you take off with lower gears. The higher the gear, the more likely it will die.

[roadster fan]

You say you set the TPS in the "midde". Not really sure what that means but the Clymer manual gives a specific procedure for adjusting the TPS: it involves the Throttle valve being completely closed, adjusting the switch till it closes (reads 0 ohms across pins 14 and 17) then rotating the switch counterclockwise one major graduation on the scales next to the slotted holes (2 degrees). Tighten the screws up and put it all back together.

Since it is all apart, I would remove the four screws holding the TPS switch cover on and make sure all is clean inside and that the switch hasn't worn a grove completely thru the contacts in the switch. The downside to the location of the TPS on a 1.7 is you cannot adjust it with the throttle body mounted in the car.

Hope this helps. The hunting idle is usually a symptom of vacuum leaks. I am going to go back and look at your symptoms again not sure the TPS is your problem.

Jim

[stateofidleness]

thanks rand, makes sense.. so i guess when it dies it 3rd it is to be expected

Jim, i will (ughh) disassemble the thing again tonight and check the actual board inside.

I wasnt getting a reading on the ohm meter when testing the pins so i really didnt know how to rotate it "until it reached 0" because it stayed at 0... so that is why i just set it in the middle, being the middle of the grooves.. not skewed to one side or the other.

i will also double check vacuum leaks again (best way to do this?)

[roadster fan]

Here is another idea. I burned up a set of points awhile back when I was doing a bunch of electrical cleanup under the dash by leaving the key in on position while checking my work. I forgot to disconnect the coil/points (IMG:style_emoticons/default/headbang.gif) . My car ran like crap, wouldn't idle, and drove me nuts because I didnt think to look at the points as they only had about 200 miles on them.

Finally thought to look there, looked like toast, put in a new set......... (IMG:style_emoticons/default/burnout.gif)

Jim