I've completed my 1.8 to 2.0 motor swap and have my car running really good, except the TPS is worn right around the partially open throttle position.

I've cleaned the surface and the contacts with 2000 grit sandpaper and then used Deoxit electrial contact cleaner. This helped as it only hesitates/bucks at the barely open throttle position and cleared up the issue at positions further along the path of travel. I imagine that it's worn right at the spot where you're most often running at.

I searched but couldn't find any threads on repairing this. What I want to do is move the circuit board to the right or left, so that the contacts run on a fresh part of the board. Any ideas on how to separate the circuit board from the metal body and how best to reattach it? It looks like it may be soldered at the bottom right corner.

Click to view attachment

Using careful pressure, you can slightly bend the 'fingers' to run on a new area of the circuit board. No need to make it more complicated than that.

Thanks McMark. I did as you suggested and gently pulled the contact arm out a little and got it to run on a new path just outside of the existing path. Put it all back together and reinstalled it, calibrated it and drove it. No more hesitation/bucking. Problem solved.

I think this may have already been mentioned, but Otto is out of the new TPS's.

He instructed me to use a pencil eraser on the switch, which works really really well. The contact strips on mine are bright and shiny now and my bucking is gone.

However judging from the grooves I would venture to guess that I will need a new one eventually.

I was looking into using Eagle CAD to make a schematic and then exploring options for having them manufactured.

Is anyone else doing this? I don't want to jump in on a project that is already being done, nor do I want to compete with anyone.

Is there any interest from the community in having these made?

There's always interest for repro parts. This part is a popular candidate. Of course it will always come down to how much they will co$t.

I fixed mine in about 10 minutes, from start to finish. It should be good for another 50,000 miles or so. That fix might kill the market for this part.

It may kill it for some but for others I suspect that cleaning won't be enough. I just noticed a hestitation or two while driving at lunch 5 minutes ago. Not nearly as drastic as it was before, but still noticeable. It may have something to do with the deceleration fuel cut-off since mine is a '76 . But I'm guessing my TPS is just a little to worn in some spots.

Does anyone know what Otto was selling his units for? If it was somewhere between $150-$200 then it getting these made would be doable depending on the number produced at intial manufacture. SRP any less than that and it would be a loss.

Isnt that gold?
Could gold leafbe applied tofix the groove?
Even silver solder might work?

Rich

I have a board house manufacturing these circuit boards right now. I expect the shipment on 22 June 09.

Awesome!!! Then I will drop the whole idea and buy one from you. Thanks for doing that!!!!!

The the original on my 72 was never as worn as yours, I puleld it for grins & used a jeweler's rouge cloth on it. Of course, you can't remove all of the groove, but it did clean up the groove & made better contact. Seems to work just fine - no bucks, etc.

I have a brand new one on the shelf, so there was so relief in knowing that if I screwed the original I could just slap on the new one.
Pat

Now that's a pretty simple damn solution (SDS get it?)!

Circuit boards arrived. Here's a pic. Testing this week.

More pics of initial board installation in this thread over on the club site.

Posting pictures here is apparently difficult.

Yeah, that's a really good picture on the other site...
It looks just like this.......

"This pic shows how the connector sits slightly higher due to the now-loose fit. (The connector should sit flush with the metal base.)

Attached File(s)
DSCN3982.JPG ( 722.59K ) Number of downloads: 3"

And It won't download....

No, not difficult. Just frustrating. Two sites, same content, same users. It's easier to post a link than to redo the whole thread. Whatever, here ya go...

First, drill out the hole for the factory rivet to 3/32". The rivet hole in the new board is sized for a 3/32" pop rivet, which will be included with the board. For those who have forgotten what a drill-bit looks like, here is a pic:

A business card makes a good ramp for getting the wipers onto the board.

Here's a pic of the board with the business card removed. No rivet yet.

Rivet installed. I would urge you to fend off the temptation to step up to a 1/8" diameter rivet. The larger head will short out the trace on the board. The correct rivet will be included with the board. Use it.

Here is a pic with the connector reinstalled onto the sensor base. I found that the plastic of the connector cracked when I removed it from the base, so now, it isn't held as securely. You'll avoid this possibility if you leave the connector in place when doing the board replacement. It'll be a little more difficult to get the board into place under the connector contacts, but the business-card trick will be helpful.

Yeah, about 1% of the same content and same users.

Thanks for making these Dave...we have been in need for too long.

Can you tell us why you did not select a screw and used a rivet?

Gee Jeff,

The answer to that is obvious....

Concours weenies wouldn't buy them if a screw was used......

Jeff,

I considered a screw. You could make it work, but here's why I didn't:
1. OE hole is roughly 1.5mm diameter. Tiny.
2. You could thread the baseplate, but a few problems are: 1.5mm base thickness means very few threads, most people don't have tiny taps, and tapping is very error-prone (some people would be successful, but probably 50% wouldn't).
3. You could use a screw/nut combination, but only at the risk of the tiny fastener coming loose. Locknuts aren't available in smaller than 3mm, so you'd be drilling out the hole anyway.
4. Those tiny fasteners are fiddly and disproportionately expensive.

So much for the cons, here are the pros:
1. A rivet will hold tight.
2. A rivet won't fail due to engine heat.
3. A rivet is cheap.
4. A rivet is so easy to install, a caveman could do it.

I wish I could have gotten a pop-rivet that matched the factory diameter, but no luck. I don't like having to drill out the baseplate, but I think on balance it's the best choice -- functionality at the expense of a slight deviation from the factory design. I know the tradeoff won't work for Pat Garvey (bless his concours heart), but the rest of us will probably agree it's worthwhile.

That seems well thought out Dave. While a screw could be used, it may loosen up and a rivet can always be drilled and replaced in kind. Kudos too you.

Can you sell these direct or is the only way to get them is through BRAG?

Jeff, either one of us will take your money. $35.00 for the board and the rivet. I'll need a week or so to validate the design on a running car before I'm ready to start shipping.

Subscribed to this thread. This looks awesome. Nice job! I'll purchase one, maybe two, once they're ready to ship.

Thats great! I would be happy to be a 2.0L mule for you if you need one.

Dave,
Outstanding job. I remember doing some small PC boards back in electronics school. We used a photo etching process for them. Wish I had a 914 back then. Ha. I'm in for one when you start shipping. Again really nice work.
Tom

Even though I fixed mine (at least temporarily), I'll be getting one of these once they've been tested.

Question: Is the conductive material on the board as durable as the original?

Cevan, if you look closely at the pics, you can see marks on the board from the wiper contacts. So it's valid to question the durability of the board. A few points of explanation:

1. For some reason, the marks appear more prominent in the pic than they do in person. I guess something to do with the reflective trace material?
2. Having said that, there is definitely a burnished region where the contacts run, just as with the factory design. We've got a spring-steel contact rubbing across a tin-plated copper trace. Witness mark are inevitable. It's definitely not "serious wear" though. (At least not yet -- it will be serious someday, but it will take a while.)
3. I called out a copper thickness roughly twice what the factory used. I also called out a tin plate, which is why these tracks are silver-colored, as opposed to the factory's raw copper. I would expect these new tracks to last at least as long as the factory design, and probably much longer. Sorry, won't last forever, though.

How about JB Weld? Wouldn't that work even better?



Nice job on the board, I'll be interested in the test results.


Warrenoliver

Funny that you mention adhesive, Warren, because that's exactly what the factory used to secure the board on the early 1.7 liter cars. I just learned this today when I opened up a 1.7 liter TPS. Although the boards are similar, they will NOT interchange. And as I mentioned, the early 1.7 liter board is glued in place, rather than riveted.

So for now, I don't have an early 1.7 liter solution. (But when I do, JB Weld might be part of it...)

Meanwhile, I'm still on the hunt for a 2.0 liter validation platform. Stand by.

PS. Thanks to Britain Smith for dissassembling his car for me.

The Cap'n will have yer hide for suggesting that!


Warrenoliver

Everyone, I still haven't found a suitable test platform. I'm looking for a 2.0 liter car, running the stock djet fuel injection in the Portland, OR area. The car should have a bad TPS, but should have no other FI-related problems.

If you have such a car, please let me know. I will install a new TPS board at no expense to you.

Thanks.

dave a ,local shop told me AA has the boards too ? can you confirm ?
yours ? or their own ?

Probably mine. Last week, George expressed interest in purchasing them. When we spoke, he didn't indicate that he had another source.

Glad to hear he's preselling them. Now I just need to get a validation platform...

I've got a late 1.7liter TPS here. It appears to rotate backward from the 2.0liter.

Can anybody verify that the 1.7liter djet throttlebody rotates backward from the 2.0liter throttlebody?

Thanks.

(By the way, although the two boards (late 1.7liter and 2.0liter) are identical in shape, they differ slightly in their copper pattern. Hence, the 1.7 will require a new board.)

I'm wishing my Seattle teener was in Portland to be a guinea pig for you. I'll be looking into whether the TPS is the root of some hesitation issues soon. At least I know where to get one if needed.

Great job making this part available again!

Jeff Bowlsby installed the board on his 2.0liter. His initial report is that the car runs as intended with the replacement board.

I've still got a tentative 2nd validation car lined up in Seattle this week. I'm getting close to releasing these for purchase.

Thanks for helping Mark . Jeff

I have a 76 2.0 that is local. Unfortunately, I still have some issues that I'm trying to work out. It runs, but after it gets warm the idle drops down. If you just want to check function it could work for you.

Just PM me.

Bump! I REALLY want two of these ASAP. Any progress? Taking the 914 from Santa Rosa to San Diego and back in mid-august and I'd love to have at least one before I leave. My other 914 could use one too! Both are 2 liter cars with stock FI.

OK everybody, sorry for the delay. I've completed the testing of the boards. $35.00 each. Ready to ship.

Hooray! How do we order?

You can either send me a Paypal (contact me via PM for address) or you can order through BRAG via the other site.

I ordered two! Who's next?

*bump*

Randy, I sent out your boards today. Thanks for the order.