TPS Adjustment

[Shade133]

sorry to revive a 3 year old post. but i have a question about this subject, and thought id ask it here instead of starting a new thread.

as stated the idle point should disconnect at any throttle movement above idle.

now my question is when should the WOT point connect? should it connect litterally only when the trottle is slammed to the floor? or should it connect a little before then? or should it connect the second the tps moves into stage 3? (1 being idle 2 being coast and 3 being anything above that)

[sblake01]

The full throttle contacts should be set to close only when the throttle valve is at full throttle. I think the book says something like more than a 34 degree opening of the throttle valve but that's pretty much the same as 'slammed to the floor' as you put it.

[Shade133]

ok perfect thanks. ive been trying to adjust the points on my tps. as it sat before i messed with it. the idle would stay connected probably until 2500 rpms and then right after it would connect to the WOT contact.

as you might imagine, my car was running like crap.

so thanks for the info!

[sblake01]

Considering the design, that shouldn't happen unless the points are sticking or somehow damaged.

[Shade133]

thats what im trying to figure out.. as of right now it looks like someone went in there and bent them to close together.. so im going to clean them and bend them back to somewhat normal by looking at reletive pictures.. and if i still cant get it to work correctly, ill get a new one for 60 bucks.

[chaseincats]

Sorry to bump a 10 year thread up but I'm a bit confused.  Should I adjust my TPS so that the idle pin disengages from the center pin with pedal movement or at 1400 rpm?

[siteunseen]

Post #8 has what I went by on my '77. I adjusted according to that then went to my mechainic and he bent the vanes by hand. Made me mad at first but it runs great. 

That has been my biggest lesson on the efi cars. There's a lot of small BS parts that aren't that important. Guys that know the cars since the '70s know all the tricks. 

[Captain Obvious]

I took a quick look through some of the docs and there appears to be three methods for setting the switch.

First method is the "measure the angle of the throttle valve at which the switch opens" method. Page EF-56 (of the 75 FSM) says the switch should open when the throttle valve reaches about 7 degrees. (Note that page EF-57 of the 77 FSM says 4 degrees).

Second method is the "measure the gap between the throttle linkage and the throttle stop" on the throttle body method. This method is described on page EF-62 (75 FSM) and EF-63 (77 FSM). They say this is how you adjust the switch if you have the throttle body loose on a bench and are replacing the switch. I don't know why they didn't employ this method all the time? Maybe because it's difficult to do with the throttle body on the car?

Third method is the "raise the RPM to a certain level and set it so that's where the switch opens" method. This method does not seem to appear in any of the FSM's, nor does it appear in the 76 version of the FI manual (the "FI Bible"), but it DOES appear in the later (1980) version of the FI manual. Pages 126-127 of the 1980 FI Bible say to raise the idle to 1400 RPM and set the switch there.

Most notable is that the 1980 FI manual ALSO mentions the "measure the gap" method, but says you should only do that when you can't use the 1400 RPM method. They say the 1400 RPM method is the "preferred" method.

Looks to me like the 1400 RPM method superseded the previous methods? I guess I would use that if I had to?

That's the results from my book report.

Then I went downtown. To look for a job.

[chaseincats]

6 minutes ago, Captain Obvious said:

I took a quick look through some of the docs and there appears to be three methods for setting the switch.

First method is the "measure the angle of the throttle valve at which the switch opens" method. Page EF-56 (of the 75 FSM) says the switch should open when the throttle valve reaches about 7 degrees. (Note that page EF-57 of the 77 FSM says 4 degrees).

Second method is the "measure the gap between the throttle linkage and the throttle stop" on the throttle body method. This method is described on page EF-62 (75 FSM) and EF-63 (77 FSM). They say this is how you adjust the switch if you have the throttle body loose on a bench and are replacing the switch. I don't know why they didn't employ this method all the time? Maybe because it's difficult to do with the throttle body on the car?

Third method is the "raise the RPM to a certain level and set it so that's where the switch opens" method. This method does not seem to appear in any of the FSM's, nor does it appear in the 76 version of the FI manual (the "FI Bible"), but it DOES appear in the later (1980) version of the FI manual. Pages 126-127 of the 1980 FI Bible say to raise the idle to 1400 RPM and set the switch there.

Most notable is that the 1980 FI manual ALSO mentions the "measure the gap" method, but says you should only do that when you can't use the 1400 RPM method. They say the 1400 RPM method is the "preferred" method.

Looks to me like the 1400 RPM method superseded the previous methods? I guess I would use that if I had to?

That's the results from my book report.

Then I went downtown. To look for a job.

Gotcha so it looks like my TPS is set properly then.  Out of curiosity, why isn't TPS set like some folks above noted where the pins separate once you touch the pedal?  That would seem like the way to get better mpg and not throw extra gas in there if the car is already moving, no?

[Patcon]

Guessing...

When starting off from idle, the car is not at idle, more like 1200-1400 rpms when releasing the clutch. Leaving the enrichment,  makes the off idle engagement more stable. Also most people dont lug around in gear near 1400 rpms so it ends up being a narrow section of the power band that stays enriched but really is only used transitionally

[Captain Obvious]

10 hours ago, chaseincats said:

Out of curiosity, why isn't TPS set like some folks above noted where the pins separate once you touch the pedal?

Why isn't the TPS set that way? My guess is that it's not objective enough. All the other methods have something you can measure. "Adjust the TPS so it makes contact at idle, but as soon as you touch the pedal, it opens" isn't something I would trust thousands of tech across the country to get the same.

And to add some detail and to what Patcon alluded to (I think)... There's a big difference between 1400 RPM sitting still with no load and 1400 RPM while driving. Sitting still with no load, it really doesn't take a lot of pedal push to get the RPMs up to 1400. The idle enrichment from the ECU not only boosts the idle fuel, but also provides an additional short bump in the fuel delivery just like an accelerator pump would do when transitioning from idle to cruise. Not sure how effective it is, but the documentation says Dr. Bosch put that in there.

For a data point, I've messed around with the setting of my TPS a bunch (surprised?) and honestly, I didn't notice any difference. I've had it set where there is some pedal travel before the idle contacts open, and I've also had it set where it's a "hair trigger" just barely making contact with your foot off the pedal and would open if you so much as breathed on the linkage.

Didn't really notice any difference in how the car performed. I didn't have an A/F gauge on it though. Might have seen some results if I had that level of diagnostic tool.