CUTLASS Replace TPS or Carb?

Eddie Cutlass

Eddie Cutlass

Not-quite-so-new-guy
May 3, 2020
46
18
San Diego
Hey guys, wondering if y’all could give me a few pros and cons on either replacing the TPS or replacing the whole carb? I’m pulling a code 21 (faulty TPS). Car is a 1985 Cutlass supreme 307 Olds V8. Thanks in advance!
 
jiho

jiho

G-Body Guru
Jul 26, 2013
658
43
Are you sure the TPS itself is the problem? Could it be wiring? You should be so lucky.

If it really is the TPS ....

1. Replace the carb. You're looking at "remanufactured" (aka "reman"). But the thing is so complicated, and has so many complicated adjustments that need to be done and done right, that upon receipt it must be taken apart and all done from scratch. Because you cannot assume that whoever did it was properly trained, got out of bed the right way on that particular day, properly supervised, etc. I'm looking at one right now, and know whereof I speak. Several special purpose tools are required, which these days are hunted down on Ebay. And of course you need a rebuild kit, in addition to the always lovable shop manual.

Oh and I forgot -- Even if your reman were somehow perfect, once installed you have to adjust the idle mixture screws. This requires a dwell meter, yet another special purpose tool (at least this one is easy to find), and a time-consuming tedious procedure all its own.

Another point I forgot -- Your reman comes with the TPS adjustment hole conveniently plugged. On that, see the following ....

2. Replace the TPS. Is the TPS adjustment hole plugged? It was from the factory. There's a ridiculous procedure where you drill a tiny hole just so far without destroying anything, insert a small screw and pry on the head to pull the plug out. There's a cute hand drawing of the drilling step in the shop manual. Once past that, with the new TPS installed and the air horn back on, the new TPS must be adjusted. This requires a long-snout 2.5 mm hex socket that will fit in the hole. Once adjusted a new plug goes in the hole, or the adjustment will creep. The alternative is to use Loctite, but I don't know how well that works. A replacement plug comes in the rebuild kit.

It's your choice. I won't say "good luck" because I've been there, and your luck is already bad. :mrgreen:
 
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Clone TIE Pilot

Clone TIE Pilot

Royal Smart Person
Aug 14, 2011
2,232
113
Galaxy far far away
There is reman, then there is rebuilt. Reman means the carb is remanufacturered to new specs the reman company invented for best profit margins. Rebuild means the carb is restored to factory specs or built to specs that matches your engine specs. Replacing the carb or just the TPS will both require adjusting the sensor. If you do replace just thd TPS, you will need a putty knife to keep the accel pump and TPS plungers depressed as you reinstall the airhorn. In a pinch, you can use a plastic pen cap to adjust the TPS, though its not a bad idea to buy the special tool as it includes a jet socket.
 
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Eddie Cutlass

Eddie Cutlass

Not-quite-so-new-guy
May 3, 2020
46
18
San Diego
Are you sure the TPS itself is the problem? Could it be wiring? You should be so lucky.

If it really is the TPS ....

1. Replace the carb. You're looking at "remanufactured" (aka "reman"). But the thing is so complicated, and has so many complicated adjustments that need to be done and done right, that upon receipt it must be taken apart and all done from scratch. Because you cannot assume that whoever did it was properly trained, got out of bed the right way on that particular day, properly supervised, etc. I'm looking at one right now, and know whereof I speak. Several special purpose tools are required, which these days are hunted down on Ebay. And of course you need a rebuild kit, in addition to the always lovable shop manual.

Oh and I forgot -- Even if your reman were somehow perfect, once installed you have to adjust the idle mixture screws. This requires a dwell meter, yet another special purpose tool (at least this one is easy to find), and a time-consuming tedious procedure all its own.

Another point I forgot -- Your reman comes with the TPS adjustment hole conveniently plugged. On that, see the following ....

2. Replace the TPS. Is the TPS adjustment hole plugged? It was from the factory. There's a ridiculous procedure where you drill a tiny hole just so far without destroying anything, insert a small screw and pry on the head to pull the plug out. There's a cute hand drawing of the drilling step in the shop manual. Once past that, with the new TPS installed and the air horn back on, the new TPS must be adjusted. This requires a long-snout 2.5 mm hex socket that will fit in the hole. Once adjusted a new plug goes in the hole, or the adjustment will creep. The alternative is to use Loctite, but I don't know how well that works. A replacement plug comes in the rebuild kit.

It's your choice. I won't say "good luck" because I've been there, and your luck is already bad. :mrgreen:
Never had much luck...guess I picked the right car. 😂
Appreciate the detailed info. I’m leaning towards a new carb (reman) unless I find a carburetor guru out here in San Diego to rebuild this carb.
 
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jiho

jiho

G-Body Guru
Jul 26, 2013
658
43
Code 21 is "open TPS circuit or misadjusted." It could mean the TPS is worn out, they are a bit flimsy inside. But to me it sounds more like a wiring problem. Anyway, I'd definitely want to check it with a voltmeter first. How are you with a voltmeter?
 
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jiho

jiho

G-Body Guru
Jul 26, 2013
658
43
I’m leaning towards a new carb (reman) unless I find a carburetor guru out here in San Diego to rebuild this carb.
Others on this board may be able to recommend a good mail-in rebuilder if you don't have one there. Not a bad plan.

Even so, just be aware it would need to be tuned after installation.
 
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69hurstolds

69hurstolds

Comic Book Super Hero
Supporting Member
Jan 2, 2006
3,879
113
Your carburetor number for an 85 VIN Y 307 V8 should be 17085282.

If you need a new TPS, buy a GM/ACDelco one p/n 17078448. It's what came in it, and the one you have is probably original. If it is, 35 years in action isn't what I'd classify as flimsy IMO. I strongly advise on two parts for your G-body Olds you should never deviate from always using ACDelco brand if possible and that's the TPS and the O2 sensors. (O2 sensor--> AFS-16P, AFS-20). Bosch may make good stuff for other cars and such, but not sensors for an Olds G-body.

The only other brand of TPS I might trust is Borg Warner, aka BWD, and that's under p/n EC1014. I have reason to suspect those guys made the part for GM. But nobody I know of that's used a BWD sensor has said they've had an issue with it. However, I still would be standing pat on the Delco O2 sensors.

And, if you are running a genuine GM TPS in your carb, I will disagree that it is flimsy. It's probably the most robust brand of TPS you can find. A lot of them are still running on the factory part.

If you are not mechanically and/or electrically handy, then it's best to get the carb rebuilt correctly. I would stay away from remanufactured garbage sold in the box stores. You're going to pay a lot and get some generic chunk of aluminum that probably isn't adjusted at all close to what you have right at the moment.

For that kind of money, and if you don't have to have the car for a bit, I'd remove it, drain it of all gas and contact Everyday Performance and let them know what you got and what you need done and follow their instructions for shipping the carb to them. They can go through the carb and make it good as new again, and best of all, it's SPECIFICALLY for YOUR CAR! It's pretty much a bolt it on and go after he gets done with it. Plus, ensure to ask about upgrading to alcohol resistant rubber bits for inside the carb if you run ethanol infused gasoline.
 
jiho

jiho

G-Body Guru
Jul 26, 2013
658
43
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jiho

jiho

G-Body Guru
Jul 26, 2013
658
43
It's pretty much a bolt it on and go after he gets done with it.
It can't be. It must be tuned on-vehicle. At least idle mixture, and probably idle speed. Otherwise he'll have a hard time passing smog in San Diego.

It's even possible (ironically enough) that the TPS may need to be adjusted on-vehicle. I'd certainly want to at least check it, even after a top quality rebuild.
 
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