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new TPS


epssax

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New here, so be gentle!  I bought a 1990 Convertible in July, 2017.  Love the car and it has 62K on the odo.  I had several Corvair convertibles and they were hot, noisy, and not very comfortable for long trips.  The Reatta is smooth, quiet, responsive, rare, and gets a lot of attention.

 

Car had idle problems from the get go.  Had an old retired tech put a new idle control motor on it and after a few heat cycles the erratic idle speeds came back.  A friend and I bought a new tps sensor and pigtail.  The old pigtail was in bad shape.  We installed those and the car ran good because it was still warm.  Got it home and the next start the idle was 2000 rpm.  Re-started it and idle was 1500, then 1000, then back to 2000!  On cold start sometimes it wouldn't idle without feathering the gas pedal.

 

Got to reading and testing the new and old TPS sensor and discovered the new pigtail was wired different than the original!  Three wires on this TPS circuit, Grey, Blue, and Black.  Went back to the store and showed them my old original pigtail and he looked it up on his computer and said it was wrong!  He went to DelcoRemy site and showed me a picture of the new pigtail and it was different wiring from the original.  The grey and the black wires were reversed.  Said someone must have spliced in an incorrect pigtail.  

 

I go back home and look and no, the connector was an original one!  So, I rewired the terminal and plugged it in and instant steady, correct idle!  Now, we have to set the TPS sensor so that it read approx. .5 volts at idle(has a CEL on when idling and showing code 22).

 

I learned:  On my Reatta the pigtail is different from a standard GM TPS connector.  Don't trust an original GM part.  How to read codes with just a paperclip!  

 

Thanks for reading my journey through a little mystery.

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Welcome aboard. Thanks for posting you experience with the TPS. Why did you have to install a new TPS connector. Seems like an odd part to go bad.

 

Are you reading codes with a paperclip? You know that the Reatta has a great on-board diagnostic system that displays codes and a lot more don't you?

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Welcome aboard. Thanks for posting you experience with the TPS. Why did you have to install a new TPS connector. Seems like an odd part to go bad.

 

Are you reading codes with a paperclip? You know that the Reatta has a great on-board diagnostic system that displays codes and a lot more don't you?

 

The connector was broken in as much as the plastic 'tubes' were cracked or broken off.  Just better to have new plastic around the heat and oil.

My 1990 has a digital dash and not the CRT display.  I think that makes a difference?  Maybe not?

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You can use the temperature control to read through the Instrument Cluster. Directions are in the "HOW To" section on the top of the web site page.

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You can use the temperature control to read through the Instrument Cluster. Directions are in the "HOW To" section on the top of the web site page.

 

Thanks, I didn't know that!  I'll look for it.

 

Took it driving today for 3.5 hours, stopping, starting, interstate, city, mixed.  Here are my results on idle speed:

 

start-up around 1500

 

During a 5 mile road to interstate, it wanted to idle at 1800 when in neutral.  I shut it off and restarted and it went down to 1500.  Shut it off and restarted and it went to about 1000 rpm 

 

Drove 15 miles of interstate and when I pulled off it wanted to idle at 2000 in neutral

 

Parked it and came out and it idled at 750 in neutral.  

 

Drove a couple of miles no change.  Parked it for an hour and came out and it idled at about 700 in nuetral.

 

Drove it home 20 miles and it was idling at about 1000 rpm in neutral.  

 

PUZZLED.

 

Next I'll check the output voltage of the TPS sensor with the key on.   My friend bought me a new TEMP sensor if needed.  Oh, the check engine light comes on when I take my foot off accelerator.  Figured we didn't get the TPS in the right place.

 

Its an adventure!

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Check the TPS via the onboard diagnostics as suggested above. What the ECM sees is most important and if it is indeed indicating about .5v, it is a little high. Probably not the problem, but down closer to .42 v @ closed throttle would be better. The diagnostics will also let you observe the Idle Air Control command (counts) from the ECM and see if it is hunting around. It will move around some to try to maintain a steady idle but I suspect you may have a vacuum leak. Not uncommon for the small vacuum hoses to get brittle at this age as well as the PCV valve buried on the intake manifold behind the power steering pump. One last thing is to observe the MAF signal to see if that is stable at idle. You can tap gently on the plastic sensor housing while idling to see if it changes the idle characteristics.

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I forgot to mention I have seen the different wiring for the TPS. When I bought a little item, called a TPS enhancer, from a vendor that specialized in items for the Grand Nationals, that he mentioned there were two different ground positions used, at least that is what he used as the key to determine the difference. I don't know where the two different schemes were used, but the vin 3 engine was still being used in some GM products in 1990 as well as the vin C and vin L (in the Regal only), all 3.8 liter Buick designs.

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I would make sure the Idle Air Control is clean. That also can make the idle "dance"...

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I would make sure the Idle Air Control is clean. That also can make the idle "dance"...

 

It has a new IAC motor.  I also cleaned out a little filmy stuff in the throttle butterfly area.

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Did you the clean area inside the hole where the pintle of the IAC motor seats? It is important that the seating surface is clean.

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Did you the clean area inside the hole where the pintle of the IAC motor seats? It is important that the seating surface is clean.

 

No, didn't know about that.  I'll see if I can get that done.

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Thanks, I didn't know that!  I'll look for it.

 

Took it driving today for 3.5 hours, stopping, starting, interstate, city, mixed.  Here are my results on idle speed:

 

start-up around 1500

 

During a 5 mile road to interstate, it wanted to idle at 1800 when in neutral.  I shut it off and restarted and it went down to 1500.  Shut it off and restarted and it went to about 1000 rpm 

 

Drove 15 miles of interstate and when I pulled off it wanted to idle at 2000 in neutral

 

Parked it and came out and it idled at 750 in neutral.  

 

Drove a couple of miles no change.  Parked it for an hour and came out and it idled at about 700 in nuetral.

 

Drove it home 20 miles and it was idling at about 1000 rpm in neutral.  

 

PUZZLED.

 

Next I'll check the output voltage of the TPS sensor with the key on.   My friend bought me a new TEMP sensor if needed.  Oh, the check engine light comes on when I take my foot off accelerator.  Figured we didn't get the TPS in the right place.

 

Its an adventure!

Don't know if you fixed your problem or not but thought you could use this information. On the TPS is a blue wire using a digital volt meter set on 12V probe the blue wire with the poss. lead and ground the neg. lead get in the car a put the accelerator to the floor with the key in the run position and the meter should read 4.5v if it is less then that go under the hood (key still on) and turn the throttle valve to wide open throttle if it now reads 4.5v shorten the accelerator cable and reread from inside the car. If the reading is the same inside or out and it is less then 4.5v then just loosen the TPS enough to turn, hold the throttle valve wide open and turn until it reads 4.5v on wide open throttle.

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  • 1 year later...

After going thru replacing a lot of parts, the Buick Roadster is now very solid and running like new.  Answer was the main computer was going bad.  Once the Computer was replaced,  my Buick Reatta Convertible started to act like any modern fuel-injected car.  Good idle, good acceleration, increase in MPG, good hot and cold starts!  Now that it is once again in tip-top shape its turns COLD!  Thanks for all your help and tips.  

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