1985 LTD TPS Repair-Replacement

My '85 LTD has had a stumble/miss under 3000 RPM and it only just stated a month or so ago. I have been wondering when the FI system sensors would start to give me grief because the bike now has 139,000 Km on it (I've put 24,000 Kms on it in the past 19 months even with the work downtime). 33 year old sensors degrade and are affected by heat.

I read where the PB (pressure barometric) can cause this so I tested them, within spec and tried the system with one detached then the other. The bike will run with only one PB hooked up. Hoping this was the issue but no joy.

Checked the Gr/Gl camshaft sensor as well. Other than the air gap being to wide - quick fix - these are good as well.

Tested the TPS for resistance and it came in at 2.6K instead of between 4K and 6K. This is the one sensor I did not want to have go. I also have the alt mod as well that is going to make this repair more challenging.

I have the bike apart and took the TPS out. I have read the PDF files on replacing the TPS with an automotive TPS or a BEI-Duncan rheostat.

To get to the TPS, I had to remove the lower fairings, take off the rad, and remove the cover plate that provides cover for the upper part of the engine.

Here you can see the TPS with all the interference items removed: The securing bolts have break off heads leaving a rounded head: I used a dremel tool to slot the TPS bolts and got lucky taking them out:

I cut the wires below the fairing and can splice/attach new wires. I did this so I could keep the OEM connector, I had already spliced in some wire taps so I could test the TPS at regular intervals, and I did not want to go through the hassle of routing new wires through the plethora of wires that are present.

Since the TPS is going to be replaced, I decided to take it apart to see what makes it tick. Here is a disassembled TPS: Here is a picture of the rheostat and internal workings of the TPS:

I will be taking the rheostat to my local electrical/electronic shop tomorrow to have a chin wag about a possible replacement.

Good day all round, especially getting the TPS out without too much of a hassle. While I have the engine coolant drained, intend to remove the air valve and clean it as well.

More to follow.

Cheers

Good work, but it is a lot of work.

Love the thread here great work I'm learning a lot....

Checked the resistance since last night, still under 4K - no way around it. Using the dremel tool was not my original idea. A fellow over on Steve Saunder's forum - Pauln - who did the PDF files as well, mentioned that was how he removed his TPS. He did not get as lucky as I, he had to grind one of the bolts off.

Took off the air valve as well, it was on my list and the coolant was drained. Put some liquid plumber in the water side, let it stand for 20 minutes and rinsed with hot water, no crud came out so I'm happy about this.These older machines sure keep you

In doing the air valve, noticed the hoses are cracking at the ends. Another item to add to the list - hoses of all varieties. I'm catching up to Mr. McGovern regarding items to be and are addressed - LOL. :clapping:

These old bikes keep one going.

Cheers

Did you find any numbers on the old TPS?

opcorn: Good work Ernest, LTD,s are beautiful bikes.

[url=https://www.classicgoldwings.com/forum/viewtopic.php?p=193105#p193105:24p6nyiz said:

slabghost » Today, 2:16 am[/url]":24p6nyiz]
Did you find any numbers on the old TPS?

Click to expand...

4913 - looked on line and nothing pops up relating to the TPS.

Checked with a local electronics/electrical shop and they were interested in what I brought in but had no recommendations. Plan B is to remove the one from the bike at my brother's place in northern Ontario. Plan C would be to retrofit an auto TPS. Plan D is to rebuild the original TPS with something (?).

Lots of options.

Cheers

Maybe this could be adapted?
https://www.carparts.com/details/Honda/A ... lsrc=aw.ds

Checked on line at carparts.com and they have a Canadian site. The same sensor shipped in Canada from their affiliate Canada Parts Online is $18.80 USD with a shipping charge of $28.00 USD for a whopping total of approximately $46.00 USD and with the exchange approximately $58.00 CDN.

Talk about the shaft eh what! :rant:

Cheers

Try a Canadian search for Honda Accura or Accord tps.

Did an eBay search and have ordered a set of 5 TPS sensors for Honda Civic/Acura/Prelude for $28.00 CDN shipped out of the east, but for that price I can replace it every year.

Going to prep the shaft to accept the new sensor. Hopefully the alternator will not be an issue.

Cheers

I hope these work out well for you.

I'm hoping that the TPS in the bike in Ontario is good; however, if not, I will be using one of these aftermarket TPS units. I have to review the documentation I have and determine if I can do some up front prep work to shorten the time when these arrive.

Even if the TPS from the bike is still good it is 33 years old and used, the bike has 105,000 Kms on it - up here that is considered a lot. I still remember when we thought in miles.

Cheers

Just back from Ontario and my sister's birthday party. Good time was had by all.

Took some parts off the '85 LTD in Ontario. Brought back the TPS, PB sensors, Gr/Gl camshaft sensors, and a few other parts. Had another look at the bike and have come to the realization that a bike sitting outside for a couple of years will need more time and energy thatn I'm willing to spend on it at this time. It will provide me with lots of spare parts that I know I might need.

Installed the TPS today. Tested the resistance and it was within spec at 4.2 K. Set it up at 0.47 VDC, changed out the refurbished auto injectors for the cleaned, flow tested and balanced original injectors (the refurbished auto injectors will not go to waste I'm sure). Put in about half a jug of anti-freeze then ran out - get more tomorrow; however, had enough that I was able to start the bike to make sure I did everything correctly.

Tomorrow is installing the alternator, finish filling up with coolant, then a road test. I will only be doing one sensor at a time if necessary to ensure I isolate the issue to a specific part.

Will be having my brother send out the exhaust and a few other smaller items that I need to replace on my bike here. Going to be a good redo.

I will be going back for a couple of weeks at Christmas and will be taking more specific items off the bike as well as taking the engine out. When I was back in March I rolled the engine over and it was good. Hopefully that was a good sign.

I have some Honda auto TPS ordered and it would be good to fit one of these on the throttle body for a fix later on.

More to follow. Cheers

I'm really into this work your doing and posting on FI bikes ...thanks great info and how to go through it all...

Have installed the TPS from the bike in Ontario and the stumble is still there. Brought back the PB sensors, Gr/Gl as well and installed them one at a time and still the same issue. The only sensor I did not bring back was the Ns sensor (crankshaft sensor). I will be testing it for resistance today.

The issue I have is there are no error codes on the ECU when cold or at operating temp. This tells me that the sensor that is giving me grief is just good enough that the ECU signals are adequate to operate the bike.

I have a thread somewhere - these get blurred after a while and a fellow commented on the information from the service manual regarding the operation and what each sensor does.

In the service manual it mentions that the Gr/Gl sensors and the Ns sensor send signals to the ECU to do virtually the same thing - control the fuel injection and ignition timing. It was mentioned that the Ns sensor (crankshaft sensor) controls timing whereas the Gr/Gl sensor on the right cylinder head (camshaft sensors) control fuel injection. This makes more sense to me.

The Ns sensor sends a signal that is predicated on where the crankshaft is and where the pistons are and therefore, the ECU knows when to fire each cylinder. The Gr/Gl sensors (camshaft sensor) signal is used in conjunction with the Ns sensor and fires the injectors, allowing fuel into the respective cylinder on the intake stroke.

Always a good experience when learning something. More to follow.

Received the new '85 Aspy/Interstate PG sensors today and have started the install. Noticed that the mounting arrangement is such that when the sensor(s) are installed the air gap is within spec, and no adjustment is necessary. I will be installing both sensors, and only hook up one. The second will be installed and if the one I'm using malfunctions, I will only have to change the connector under the shelter without having to take the front off the bike (again). Will post pictures a bit later. More to follow.

Cheers