[scooter111]

1983 Seville, 4.1
I posted last month about an issue with her almost stalling and having to "bounce" on the gas pedal to keep her running while waiting for a construction crew to clear the road on my way back from a battery purchase. (Details in previous post) After checking codes, fuel pressure etc. I decided to replace the TPS and ISC motor as a precautionary measure. Well, let the fun begin! First of all, the idiot who installed the TPS over torqued one of the attachment screws and it broke flush with the base housing. So he glued it in! Everything has to come off the intake to remove the base so it can be drilled out and retapped. After 36 years the bolts for the attached parts are gaulded to the intake as are the various pipes etc attached to the fuel intake base. And trying to get to the mounting bolts and connecting tubing requires removing other sensors, also gaulded, along with the distributor. A real nightmare, I don't look forward to removing the intake manifold to drill out all of the twisted off bolts so in a flash of possibly unsophisticated thought, I am thinking to just fugetaboutit and remove the TPS and ISC motor completely. After all I can adjust the idle up or down with the throttle screw. Don't think it would be a big deal to do that, might set a code or two, but so what? The TPS and ISC are only idle control functions and seem, at least to me, to be add-on electronic gizmos that add nothing to the run-ability of the engine, just being idle control.

I am probably missing something in my reasoning, (trying to save a lot of additional work and aggravation) and would appreciate any input from anyone who has been faced with a similar situation. And,as an addendum, NO, the base cannot be drilled out while still in position on the car.

 

[smokuspollutus]

Whoa. One step at a time, it's a pain right now but not impossible.

You can in theory operate without the ISC-it will make cold starting difficult and warm running wasteful, but it can run without it by adjusting the minimum air screw as you mention. But you're throwing the baby out with the bathwater by doing that.

However, It will not run worth a damn at any engine speed without the TPS installed. Without it moving in correspondence to the throttle the car will have no idea how much fuel to flow, advance to give, when to open the EGR, etc. etc. as you drive.

To remove the throttle body the only pieces of any concern are wrecking the fuel supply and return. Possibly the metal vacuum line which is also attached similarly. A set of line wrenches really pay for themselves with stuff like this and I suspect with a little penetrating oil you'll be good to go. Once they get loose you have the 3 (13mm?) bolts holding the assembly to the manifold. You may need a deep socket. I have NEVER come into one that was difficult to remove however. Then the two probably fossilized rubber hoses at the front and back of the throttle body and the whole assembly can be removed from the car and the repair made.

 

[Ranger]

First of all, the idiot who installed the TPS over torqued one of the attachment screws and it broke flush with the base housing.

It most likely was not over torqued. Steel screws in aluminum threads will eventually corrode due to galvanic action, much like a steel bolt rusted in place. Too late now, but next time, give the screw head a good whack with a hammer. That will likely break the corrosion and allow the screw to be easily removed.

 

[scottelderado]

Scooter, I can tell you driving without a working ISC is no fun. But it is possible.
My ISC was on the fritz so I disconnected it temporarily. Lots of stalls after cold starts, some stalls even after warm starts. I couldn't use AC because the car would stall at a stop, mid drive (insufficient RPMs). I'd have to rev the engine in Neutral to keep it running before putting it in gear, which, of course, caused a jolt when you put the car in gear. That requires some running room to do safely. One time I took out a wooden fence overdoing it in reverse.

Can't be re-tapped, a little bigger?

 

[scooter111]

Scooter, I can tell you driving without a working ISC is no fun. But it is possible.
My ISC was on the fritz so I disconnected it temporarily. Lots of stalls after cold starts, some stalls even after warm starts. I couldn't use AC because the car would stall at a stop, mid drive (insufficient RPMs). I'd have to rev the engine in Neutral to keep it running before putting it in gear, which, of course, caused a jolt when you put the car in gear. That requires some running room to do safely. One time I took out a wooden fence overdoing it in reverse.

Can't be re-tapped, a little bigger?

Scott... You are right on target! At first, I tried driving her with both TPS and ISC disconnected but mounted in position. Same result as you described but without the fence. Then I installed the new TPS (using only one screw to hold it in place) and ISC units just to see what would happen while the PB Blaster was working its magic on the fittings. Both are now connected electrically and she doesn't run worth crap: as you indicated, constantly stalling, etc. I am now thinking there is another problem because with both new units connected, the running problem should have been solved. But, of course, there is something else wrong. My current hypothesis is the computer is on the fritz as it is supposedly the controlling influence although I can't trace the wiring schematics from 'puter to either TPS or ISC. Guess I'll just have to bite the bullet and try that next after I drill out the broken screw piece. Just the wonderful world of Cadillac overdoing the electronics when it could have been done much more simply. Anyway, I keep trying to loosen the fittings on the base plate without destroying the piping, hope I'm successful with that.

As a side note, the FSM says there is no idle throttle adjustment that can be made: Au' Contraire, mon ami. Note to Cadillac engineers: there is an adjustment screw hidden just in front of the ISC motor which is fully capable of doing just that. Granted no fuel/air mixture available on the DFI but you can increase/decrease the idle throttle speed at your convenience. So why is the ISC needed? Rhetorical question.

AND, I could probably write a novel about the horrors pertaining to the original automatic antenna regarding the design, removal, repair and placement of said unit !! But I still love the car. What did I expect from a female.

 

[scottelderado]

I have a fix for the antenna. Cut the mast off carefully with a hacksaw blade and tape over the hole That's what I did.

You're probably aware, but if you don't calibrate the ISC and TPS perfectly and at the same time, it'll never work right. It's real hard and the steps in the FSM must be followed. Even pro mechanics will screw it up because they approach it like a modern car and wrongly see no need to follow the steps in the FSM. There are no shortcuts for that calibration.

Smokus will probably chime in again soon... do what he says. He knows this stuff.

 

[scottelderado]

p.s. I'm just a parts changer, but in your situation I'd consider screwing in the TPS screws again, using the existing holes, but with Loctite. Seems possible that might hold, even if stripped. I would not, however, use anything permanent or stronger than thread locker.

 

[scottelderado]

p.p.s. Reread your first post: Oh, the mechanic broke the screw head off, so the screw shaft is stuck in there, with no head? Yikes.

 

[Mr Earl]

Maybe you should rename her. Christine was a Plymouth, the Eldorado is probably not happy with that name.

 

[scottelderado]

Apparently Christine is a Seville, which checks out. My EldoradO is clearly male.

 

[Mr Earl]

My mistake didn't read for comprehension. I would suggest a new name, I am putting forth... Carmen. The opera of that name takes place in Seville.

 

[scooter111]

Maybe you should rename her. Christine was a Plymouth, the Eldorado is probably not happy with that name.

Mr. Earl... Took the liberty to name her "Christine" because of the jealous way she reacted to being in the same proximity to the manly 1999 Eldo. Seems she decided to hoard all the attention to her so I would not pay attention to the Eldo. Now keep them separated on opposite sides of the garage. Seems to work.

 

[scottelderado]

Related: I once met a woman named "Eldorada," named after her dad's favorite car. (She said: "Hi there, I'm named after your car...").
I greatly appreciated the attention to gender/suffix naming convention.

 

[scooter111]

I have a fix for the antenna. Cut the mast off carefully with a hacksaw blade and tape over the hole That's what I did.

You're probably aware, but if you don't calibrate the ISC and TPS perfectly and at the same time, it'll never work right. It's real hard and the steps in the FSM must be followed. Even pro mechanics will screw it up because they approach it like a modern car and wrongly see no need to follow the steps in the FSM. There are no shortcuts for that calibration.

Smokus will probably chime in again soon... do what he says. He knows this stuff.

Scott... Being a dumb red-neck from WV, I removed the antenna: Popped the hood and took the hinge off to access the antenna through the fender opening, removed it sent it to Texas for repair (THREE times), finally trashed it and bought a universal unit to replace it. Now that one stopped working. Here we go again. I sometimes wish I wasn't so anal.

Followed the FSM as much as I understood it when installing the TPS and ISC. What a PITA. As I said, GM could have done it another way and achieved possibly better functionality. Too much electronic wizardry to accomplish such a simple task.

 

[scottelderado]

At first, I started down that fender-removal route, hoping to save the mast. But stopped halfway, then never got around to finishing removal, then needed a car cover... so simply cut it off. I really wanted to make it work, just because, and if I still had the mast I'd probably try to rebuild it using steel cored weedwhacker line and Gorilla epoxy. But that antenna ship has sailed for me. New mast is like $140.

The ISC/TPS calibration is a well-known PITA in the HT4100. People here say it's actually achievable by a layman. If mine requires recalibration again, I'll give it a go, but last time I gave up and paid a garage to do it. (By the way, that garage screwed it up the first time and I had to insist they do it again, correctly, following the FSM).

 

[scottelderado]

... surely there are dozens of "how to calibrate the ISC/TPS" threads on here. Poke around.

 

[scottelderado]

Consider something like this?: https://www.amazon.com/Alden-4507P-Grabit-Broken-Extractor/dp/B000Q60UOO

Advertised as good for as small as 3mm (a 3mm screw head, that is. But I figure the screw shaft in your case may be about 3mm. Do I know what I'm talking about? No).

 

[scooter111]

Consider something like this?: https://www.amazon.com/Alden-4507P-Grabit-Broken-Extractor/dp/B000Q60UOO

Advertised as good for as small as 3mm (a 3mm screw head, that is. But I figure the screw shaft in your case may be about 3mm. Do I know what I'm talking about? No).

Scott... Checked it out on Amazon. These things have been advertised for years, once in a while on TV, "but wait we will double the offer if you ..blah,blah,blah". They are designed for use when you have a rounded out screw head, won't work on snapped off bolts. Generally they are not effective as the tips break, poor steel. You are better off with an easy-out after drilling if you can even get the drill in line with the affected bolt. Might work on some mild steel but its like anything else, mostly advertising crap. But thanks for the thought, appreciate it.

 

[scooter111]

Has anyone ever heard of Murphy"s Law? I think I must be a relative of his. Just thought I would follow up on my TPS/ISC repair issue on "Christine" and convey my thanks for the insight I received from your many comments.

I finally got the new TPS/ISC units installed with the following tribulations: Maybe my EGR valve is different than what others have encountered with their car, but the one vacuum fitting right under it cannot be loosened with anything short of using a hammer and chisel on the EGR bolt to get it loose enough to raise it so the line wrench can get on the line. What a hassle! Then, when everything was unbolted and the throttle body came loose I could not remove it without cutting the wires to the injectors so I had to drill out the broken/glued, (yes, it was glued in) TPS screw remnant while it was on the car. But wait! The new TPS came with new screws, but instead of the original 8-32 screws, the new unit had 10-32 screws which necessitated drilling and tapping both screw holes. Of course the broken off piece in the throttle body could not be drilled exactly because of the broken edge, so the new bolt was too tight and the TPS could not be turned for the adjustment it needed. So the TPS elongated slots had to be drilled also to accommodate the new fatter screws. But I got it together, bolted up and she actually runs with no left over parts. My attempts to set the proper parameters for the TPS and ISC were limited although I followed the FSM to the letter as best I could. I have decided to let my repair buddy with his $1,000 diagnostic reader do the final adjustments for me to assure accuracy. Wise solution.

As an aside, I traced the wiring from the computer through the system. Why the TPS and ISC are interconnected with so many other sensors is absolutely amazing and a nightmare of overly aggressive complexity known only to the engineer who came up with why the (example) radio relay might play a part in the fuel control system is beyond my comprehension. Absolute overkill and we wonder about the electronic complications inherent in the new vehicles produced today. They are nothing compared to this old girl.

 

[Mr Earl]

Welcome to Canbus I think. A network system not unlike the internet that I first encountered on a missile defense project involving hydraulic actuators. A very industry standard control system.