Reptoid Overlords

TPS moisture

20 posts in this topic

Every few months or so I'm pulling the TPS out of my N/A '80ZX to find tiny amounts of moisture built up inside causing a slight miss at a specific RPM(1600-1800). Once cleaned out it runs like a golden chariot. I live in the rainy pacific NW USA where constant moisture and cold fog dominate most of the year. The car has been daily driven for the past several months while rebuilding my Jeep, so its exposed to the elements.

 

Has anyone found a decent way to seal or otherwise prevent moisture from building up in the TPS while still allowing for future removal?

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ID: 2   Posted (edited)

Don't have that issue but have you considered spraying it down with wd40? It's a water repellent. 

Thinking about it....I had the moisture issue where the harness connects to the tps. That's where I used the wd40. Not sure it'll work inside the tps.

Edited by rcb280z

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I wasn't too sure if that was OK with the electrics inside...but I'll give it a go.

 

I was hesitant to use it in the actual TPS, and it sounds like that isn't what you are suggesting. So I'm not going to do it. I've used some Deoxit D5 on the connector, which stays dry. For now, I will put TPS removal as a regular maintenance item when needed and remember how minute and trite my problem is compared to real problems that others have.

 

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Do you have room to glue a small " Desicant" bag from a bottle of Aspirin under the TPS cover? Or try sealing the TPS cover with RTV? Modern TPS's  are all sealed and that is probably the solution. Very few cars have a removable cover like the 280Z TPS. 

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A silica gel packet? Never thought of that. Thanks. I'll see if I can't get one in there.

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What's the part number? I have a new one for a 280Z...

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A22-602 420

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I'll check it tomorrow but it doesn't sound promising. Someone commented that they aren't the same.

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Thanks. I appreciate it. Not that they are related, but ignition modules from I believe '77-81 are compatible. The one I have is working and adjusted properly. According to the FSM ohmmeter check. It just likes to get wet.

 

It's the one with the rivets that fasten the black plastic cover to the metal base.

 

 

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On 3/20/2017 at 8:25 PM, Chickenman said:

Do you have room to glue a small " Desicant" bag from a bottle of Aspirin under the TPS cover? Or try sealing the TPS cover with RTV? Modern TPS's  are all sealed and that is probably the solution. Very few cars have a removable cover like the 280Z TPS. 

desiccant bags need to be redried from time to time using an oven, so i don't think putting it in there would be any more beneficial than opening it up to clean out moisture from time to time. Also, if there is a moisture leak, then it would be dehumidifying everything, not just the TPS since it's not sealed.

Use a silicon spray instead. You can drill out the two small rivets on the back, and use M5 screws to hold the cover on again after you've opened it (for anyone reading that hasn't opened theirs yet). I've done this to all my Z31 TPS's. You can even use silicon gel/grease if that's all you have.

The silicon spray will coat everything that doesn't need to short, and the finger-follower will just wipe silicon off of where they ride and make contact. 

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Thank you. That's very helpful, and I will do just that.

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ID: 12   Posted (edited)

if it makes it run like poop, you could always spray the bajeezus out of it with brake clean and try something else, but i don't think you'll ever open it up again.

put some silicon lube in the connector housing too. its a dielectric grease.

in fact, put it on every connector that doesn't have a weather seal or at least whatever you can reach. you'll instantly know if the pins on a connector need to be looked at because every male/prong pin should wipe or scrape away enough silicon from its socket/female pin in order to make contact. if you're losing contact after applying silicon grease, that means it wasn't making a great connection to begin with and the socket terminals need to be de-pinned from the connector housing and deformed just enough so that it makes good contact again with the male pin.

i bought this kit for de-pinning after trying to use various needles, and screwdrivers and round steel tubes to get some connectors out of their housing for all sorts of cars. i don't use it often, but when i need to use it, its most often the difference between doing it now or doing it another day:

EQP-004-Electrical-Terminal-Release-Kit-

but thankfully, most nissan connectors can be de-pinned with a small hair pin or sewing needle.

this is getting a little off topic- but if you end up needing to do some connector work, i can post more info or pm me and i can lead you in the right direction regarding your concerns or issues.

 

Edited by Careless

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I've replaced the fuel injector/CHT/Thermo connectors and fusable links. I was thinking of testing and cleaning the voltage drop resistor next. I had an intermittent stall that ended up being a faulty alternator hold down bolt, causing the belt to loosen. Replacing the bolt and re-tightnening the belt fixed it. Any advice or heads up about troubles regarding the voltage drop resistor would be appreciated.

 

It'll be the last electrical connection that I'm aware of that hasn't been tended to. The pocket calculator under the drivers side kick panel has been tested per FSM along with a good deoxit treatment. Ignition module appears to be functioning as intended.

 

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ID: 14   Posted (edited)

I'm not familiar with the particular part you're referring to. is it an Injector impedance box with 7 pins? one input power wire and 6 outputs to the individual injectors? some injection systems are squirted in batches or pairs, so it might only have one input wire and 2 or 3 outputs.

if so, its most likely just a cluster of resistors in there. somewhere in the FSM or online there should be an impedance measurement and pinout you can use to test if the resistors aren't blow or shorted or degrading.

Edited by Careless

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The dropping resistor, as its called, are indeed 6 resistors that reduce voltage to the injector for protection. Looks like they started using them in 280z's EFI systems. I have no cause for concern that mine is bad, but it needs to be cleaned up and tested just to make myself feel better. I was just curious if you had run into any problems with them.

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On 3/19/2017 at 11:20 AM, Reptoid Overlords said:

Every few months or so I'm pulling the TPS out of my N/A '80ZX to find tiny amounts of moisture built up inside causing a slight miss at a specific RPM(1600-1800).

That's an odd solution to the problem since the TPS (more correctly called a TVS) only changes state right off idle if adjusted correctly and again at full throttle.  Shouldn't be in the picture at all at 1600-1800 RPM.  Red herring?  Or maybe it's misadjusted.

1980 TVS.PNG

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I should've updated as I think I've diluted the thread a bit. There was moisture in my TVS, but my rpm related problem was due to the alternator hold down bolt coming loose, causing the belt to slip preventing smooth voltage distribution to wherever it needed it. I guess that rpm was just the right spot to make it run weird. Thanks for your reply.

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ID: 18   Posted (edited)

22 hours ago, Zed Head said:

That's an odd solution to the problem since the TPS (more correctly called a TVS) only changes state right off idle if adjusted correctly and again at full throttle.  Shouldn't be in the picture at all at 1600-1800 RPM.  Red herring?  Or maybe it's misadjusted.

It should be noted that Nissan TPS/TVS are known for poor contact buttons and finger-follower deformation which can change its range of response where the open/close circuit will function- mainly due to the center conductor/pin binding up when you jab the throttle sharply instead of easing into full throttle. it's only brief, but by design- over time, it can deform the contacts within the unit because of how the plastic trench that the center pin rides on is designed. the area of the trench that moves it to the open position is a short and sharp zig-zag. 

if it were misadjusted + had misaligned contacts, it might hit that RPM. can't say i've actually tested various units and recorded the number. I just prefer to just adjust them and get them working.

Nissan partially fixed the issue on the Z31 model by adding a linear potentiometer within the TVS, essentially turning the Z31 unit into a TPS, as you've mentioned- there is a difference. Though for some reason, the fix was only adopted on the automatic ECUs, even though all the TPS units had the additional 3 pin sumitomo connector hanging out the bottom/side.

Edited by Careless

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8 hours ago, Careless said:

It should be noted that Nissan TPS/TVS are known for poor contact buttons and finger-follower deformation which can change its range of response where the open/close circuit will function- mainly due to the center conductor/pin binding up when you jab the throttle sharply instead of easing into full throttle

I've never heard of this problem.  Usually they're just corroded from sitting inactive.  Never read of such a detailed flaw in the design.  Where did you get your info?

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ID: 20   Posted (edited)

I didn't "get" my info anywhere, I discovered it on my own through trial and broken parts. I have taken apart many of these TPS units. One of the first used ones I tried to diagnose issues with had a slightly deformed centre contact- the one with the button that rides the trench in the nylon base. I literally chased harness gremlins for months because I had already changed and adjusted the TPS thinking it had to be the issue with why my car was idling weird all the time- it seemed to fix the issue... or so i thought. I was wrong. I just gave up messing with it at one point until I installed Nistune and logged drives on my way to work.

After fitting my 60mm turbo, I was dicking around and seeing how fast it spools by conducting repeated closed-to-wot throttle jabs. I must have done at least 10 to 15 in succession, one after anoter. When I parked the car, it would not idle correctly. I used nistune to check TPS logs and found that it was not closing... I opened both previous units that had seemed to fail, and the one I had just taken off had a noticeable kink in the blade. The one which that one replaced the first time around was deformed, but not kinked. The blade was definitely bowed more than normal. Almost as if the nylon piece pushed it further than it could possibly move in the trench.

I have 3 or 4 more TPS units in storage because I've seen two show erratic behaviour due to the same issue, and because they're inexpensive at junkyard expeditions. 

It's a common mod to intentionally bend the 280zx blades to adjust the function of the TVS, but these were sealed Z31 or other VG30E/T units, so I ruled that out.

It's also possible that the reason they bent is that the grey stick that is what swings the nylon pieces around possibly deformed a bit causing the center pin to bottom out on the end of the trench, but I do know that they were bent before I opened them- I did not modify them. 

If you spray silicon lube on the nylon piece, they move noticeably smoother too. Maybe that says something. In any case, I'm not saying they're all doomed to fail. Manufacturing tolerances probably have a lot to do with it, and that's why they made replacements. It's still a nice and compact design.

Edited by Careless

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