Throttle Position Sensor source? Anyone have any ideas?

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Romans8

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Hi all, I'm new here. I recently was able to pick up a 1986 Aspencade that was sitting for a while. I've got it running pretty well and have enjoyed riding it a few hundred miles now. I'm having some issues with lugging/poor acceleration under 3000rpms. After that it pulls great. The Fuel System light is on as well as the code on the CFI for the TPS. I did the ohms test listed in the supplemental manual and don't get the required 4-6k ohms. So, I'm pretty sure i have a bad TPS.

I've read all the forum posts I can on modifying automobile TPS's for this application and might go that direction. I just wanted to check in here and see if anyone had any good new sources for a TPS for an 86 aspy, or new ideas for replacing/repairing the TPS.

Thanks for all the great info on this forum! I think I'm going to be referencing the collective knowledge here quite a bit!
 

Rednaxs60

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Good afternoon. I have played with a few. The aftermarket early model 1985 Honda Civic TPS is the one generally used.

Does your bike have the external alt mod - Poorboy? If so you will have to modify the Civic TPS case to fit. You can modify the aftermarket TPS so that you use the existing TPS bracket to secure the new TPS.

You have to extend the actuating arm of the Civic TPS to connect with the throttle body actuating arm.

If there is an error code as you mention, do not keep riding the bike. A faulty TPS can cause the timing to change and the engine could fire a cylinder rat the wrong time. Not a pleasant experience - experienced this first hand.

You could try to recalibrate the existing TPS for the short term, but you will have to change it out sooner than later.

The TPS is secured with break away bolts. You need to grind a slot into the bolt heads, use a Dremel. Don't be too aggressive, only grind as much as needed.

If you purchase an aftermarket TPS get a couple because a new aftermarket TPS can be faulty as well - once again, experienced this first hand.

Let us know what your intentions are.
 
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Romans8

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Thank you rednaxs60!

My bike does have the poorboy alternator. I guess I'll start by trying to get the old TPS out using a dremel and cutting slots to unscrew it. Then I'll see what kind of aftermarket or civic TPS I can find. I'm definitely not finding any of the actual, correct TPS replacement part.

Do you recommend a site or location to find a good replacement?
 

Rednaxs60

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The poorboy alt mod will challenge your hacksaw skills - use a coping saw. eBay is the best, expensive now, before C-19 could get packs of 5. Check your local parts place as well.

Once you have it out I have some suggestions regarding the mod of the TPS case. You will have to extend the TPS actuating arm. I have been experimenting with a new TPS case mod scenario that has the Civic TPS fit quite well. here's the latest rendition, fits well:

IMG_2106.JPG

You have to modify the heat shield, Dremel tool works good for cutting away excess metal. You will notice I used the original TPS holding bracket. Here is the installed original TPS with the break off bolts slotted, doesn't take a lot of work:
Break Off Bolts slotted with Dremel.jpg
Here's a picture of the original TPS taken apart. Notice the part I call the keeper. I reuse this when I install the aftermarket TPS. This is the reason I mention you have to modify the aftermarket TPS case:
TPS Disassembled.jpg
This is the aftermarket TPS you are looking for:
Aftermarket TPS 1.jpg
Good Luck
 

Rednaxs60

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To use the aftermarket TPS in this location and orientation, you have to relocate the TPS actuating arm. I used 1/8" ABS sheet and cut a small piece to suit. Used JB weld for to glue the small arm, and it gives it a lot of strength. Will be modifying one today. Will take additional pictures.

The reason I mention getting more than one, I mentioned this in my other post, is that even new ones can be faulty. better to have two or three modified to suit and ready to go.

I had this happen on a cross Canada trip. Bought an '85 Limited Edition parts bike in Ontario. Engine started after sitting for 4 or so years in the back 40. Didn't have the heart to strip it. Put it on the road with a new TPS. All sorts of timing issues. Started across Canada, did a lot of work on the way. Finally changed the TPS in Brandon Manitoba, it was a good TPS and all issues went away. Tony from down under kept telling me that the issue(s) with the bike was the TPS. He was right.

Still looking for a better TPS replacement.

Cheers
 
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Romans8

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Thank you sooooo much for all the great info… I got the alternator off after work today, then used a hack saw blade with no handle to notch the bolts. Slow process, but got it off this evening!

Now to getting the new one rigged up
 

Rednaxs60

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While you are at this, I'd recommend splicing three wires into the wiring going from the TPS to the TPS connector under the shelter. These wires would be long enough to tuck up in beside the fuse box. The reason I mention this is that you may have to do this again. Here is a pic of the calibrating wires in by the fuse box, and the TPS installed. I am using a different TPS mod, but everything should be okay.

TPS Installed:
TPS Installed.JPG
TPS Calibrating wires under shelter by the fuse box, the three wires are circled:
TPS Test Wires - 2.jpeg
 
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Romans8

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To use the aftermarket TPS in this location and orientation, you have to relocate the TPS actuating arm. I used 1/8" ABS sheet and cut a small piece to suit. Used JB weld for to glue the small arm, and it gives it a lot of strength. Will be modifying one today. Will take additional pictures.

The reason I mention getting more than one, I mentioned this in my other post, is that even new ones can be faulty. better to have two or three modified to suit and ready to go.

I had this happen on a cross Canada trip. Bought an '85 Limited Edition parts bike in Ontario. Engine started after sitting for 4 or so years in the back 40. Didn't have the heart to strip it. Put it on the road with a new TPS. All sorts of timing issues. Started across Canada, did a lot of work on the way. Finally changed the TPS in Brandon Manitoba, it was a good TPS and all issues went away. Tony from down under kept telling me that the issue(s) with the bike was the TPS. He was right.

Still looking for a better TPS replacement.

Cheers
Rednaxs60, did you get a chance to take pictures of the most recent TPS modification as you mentioned?

I received some of the recommended aftermarket TPS's in the mail and plan to attempt a mod like yours. You mentioned using the original "keeper" housing and trimming the plastic of the new TPS. Do you have any pictures to share?

I'm hoping to begin this process soon, but just want have a better grasp of what's involved and the steps I need to take.
 
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Romans8

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Do you use an o-ring or gasket? Started playing around with an actuating arm and orientation to fit everything in today! Excited to get this thing running smooth and happy
 

Rednaxs60

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Pictures! Used 2 small thin gaskets between the TPS and throttle body - use as many as required to firmly secure the TPS in position after calibration. Used the keeper and star washer on the non-throttle body side:
TPS Disassembled.jpg
To get the keeper and star washer from the original TPS, cut off the rubber protective cover.
 

Rednaxs60

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Here are some pics of a TPS modified that will tuck in nicely where the original is.

You first have to modify the heat shield remove material with a Dremel. There should be no heat shield between the TPS and frame.

I removed the securing bolt hole metal bits so as to not damage the hole saw I used. remove just enough plastic to remove the metal bits:
Aftermarket TPS.jpg
Centre the TPS in a drill press, using a hole saw size 1 3/4" remove rest of TPS base:
Modifying TPS Base.jpg
Remove the plastic from the connector. I use a scroll saw and cut straight down the inside of the tab indicated by the arrow. Cut down until you reach the main TPS body:
Case Mod 2.jpg Case Mod 1.jpg
The exposed contacts are not an issue. Next cut off the three small tabs on the TPS main body:
Case Mod 3.jpg
The keeper and star washer will now fit over and onto the new TPS.

Next thing to do is attach the new actuating arm. This arm should extend out from the TPS the same distance as the original TPS actuating arm:
Original TPS.jpg Case Mod 1.jpg
I positioned the new actuating arm about 90 degrees from the original actuating lever. Don't go quite 90 degrees. Once you have it in place with a small amount of JB Weld, cover the new arm with JB Weld, very strong and will not move or break. Leave the end of the new arm free of JB Weld.
New Actuating Arm JB Weld in place - 1.jpg
Once this work is done, you can install the new TPS and it should look like this. You will notice how much of the heat shield has to be removed. This mod positions the TPS away from the alternator. This pic shows how I protected the TPS contacts:
TPS Installed.JPG
The male connectors to use are the same size as those you will find in the male connector plugs. Once these are attached to the wires, use shrink tube to protect the connector pin. This shrink tube also prevents the connector pins from touching.

Hope these pics and the explanation helps. Cheers
 
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Romans8

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Thanks a ton for the great pics and detailed description!

The replacement TPS that I got came with a green material gasket. Do you use a standard gasket or an O ring like in your previous mod descriptions?
Here are some pics of a TPS modified that will tuck in nicely where the original is.

You first have to modify the heat shield remove material with a Dremel. There should be no heat shield between the TPS and frame.

I removed the securing bolt hole metal bits so as to not damage the hole saw I used. remove just enough plastic to remove the metal bits:
View attachment 48860
Centre the TPS in a drill press, using a hole saw size 1 3/4" remove rest of TPS base:
View attachment 48861
Remove the plastic from the connector. I use a scroll saw and cut straight down the inside of the tab indicated by the arrow. Cut down until you reach the main TPS body:
View attachment 48862 View attachment 48863
The exposed contacts are not an issue. Next cut off the three small tabs on the TPS main body:
View attachment 48864
The keeper and star washer will now fit over and onto the new TPS.

Next thing to do is attach the new actuating arm. This arm should extend out from the TPS the same distance as the original TPS actuating arm:
View attachment 48865 View attachment 48863
I positioned the new actuating arm about 90 degrees from the original actuating lever. Don't go quite 90 degrees. Once you have it in place with a small amount of JB Weld, cover the new arm with JB Weld, very strong and will not move or break. Leave the end of the new arm free of JB Weld.
View attachment 48866
Once this work is done, you can install the new TPS and it should look like this. You will notice how much of the heat shield has to be removed. This mod positions the TPS away from the alternator. This pic shows how I protected the TPS contacts:
View attachment 48867
The male connectors to use are the same size as those you will find in the male connector plugs. Once these are attached to the wires, use shrink tube to protect the connector pin. This shrink tube also prevents the connector pins from touching.

Hope these pics and the explanation helps. Cheers
Thanks a ton for the great pics and detailed description.

The replacement TPS that I got came with a green material gasket. Do you use a standard gasket or an O ring like in your previous mod descriptions?
 

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