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Old 03-31-2015, 03:03 PM   #1
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Default 1994 Olds 88 stalling issue

Good afternoon, my first post here. I am an avid poster on Ford Truck Enthusiasts so hopefully I will not be too much a newbie.

The car is an 1994 Olds 88 with a 3.8L. It is my daughter'* car and is a bit of beater, so we don't want to spend too much money on the car.

The car stalls intermittently when decelerating. It will set CEL. We had the codes read and mechanic said it was the TPS (They didn't give me the code). The mechanic claimed he replaced the CEL and the problem went away for several months and then came back. Took it back to the same shop and they claimed they couldn't fix the problem because of the throttle body?

The TPS didn't look new to me, so I used a DVM to test the it. The reference voltage was 5 volts as it should be, but the sensor out put was about 0.2 volts and it did not vary much with throttle position. I believe it should be close to 5 volts at WOT?

My questions:

1) I assume based on the voltage readings, the TPS is bad and I was going to replace it.
2) I would like to read the codes, but I am a little uncertain on how to do this. I understand that 1994 was a transition year from OBD1 to OBD2. I found a 16 pin female connector under the steering column under the dashboard. Does this make it an OBD2?
3) If it is OBD2, can I read codes with a standard code reader? I have the Auto Ingenuity PC software, an SCT tuner and a DashDaq for my truck, but I assume I can't use these.

Thank you in advance for your help!
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Old 03-31-2015, 06:29 PM   #2
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Welcome to the forums!
Here is some test info on the TPS;
https://www.gmforum.com/trouble-shoo...sensor-279319/
I am sure other members may chime in on this as well.
In DE-accellerating stall, the EGR comes to mind too.
https://www.gmforum.com/trouble-shoo...0/#post1490248
Two rows of 8 pins sure sounds like an OBDII to me, try to see if a regular reader plugs in to read the codes.
Hope this helps.
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Old 03-31-2015, 07:50 PM   #3
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1994 should be OBD 1.5, which is essentially an OBD 2 port, leading to a slightly enhanced OBD 1 computer. You will need a scanner that specifically states it is compatible with this system. Usually the place to start looking is the units that scan both OBD 1 and OBD 2.
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Old 03-31-2015, 10:15 PM   #4
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Thank you Soft Ride and Randal for the help.

I tried the TPS test procedure and this is the results:


The resistance seemed smooth, but increased as you reached WOT. Is this correct? I thought TPS voltage should increase (therefore resistance decreases) as you approach WOT?

This is the test I used Saturday:

http://easyautodiagnostics.com/gm/3.8L/how-to-test-the-throttle-position-sensor-2

IIRC the TPS should put out 0.2 - 4.8 Volts and it failed the test. It only put out about 0.1 0.2 volts no matter the throttle position.

I tried the EGR test while the EGR was mounted on the engine and I didn't hear any movement. The EGR is rusted in their pretty good, so the nuts/bolts get a soak of PB Blaster for the evening.

As far as the being able to do the scan goes, I found this post on the site:

https://www.gmforum.com/1992-1999-91...-odbii-246722/

The post used terms like "you have the dreaded hybrid year" It sounds like chances of reading codes myself is not likely.

I am thinking I will just replace the TPS ($40 ebay OEM) and see if it works. Otherwise, I will need to find someone who can work on the old girl.

Any suggestions?

Thanks again,
Don
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Old 03-31-2015, 10:38 PM   #5
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One of the big concerns is the scanner being used, which if you don't have, then you won't be able to pull codes. I have reservations about whether or not the shop can even pull these codes, especially with the oldest OBD 2 vehicle approaching 20 years old, and the likelyhood they would plan for the GM OBD 1.5 contingency is on the decline.

Another TPS may be worth a shot, but it also has me wondering why the shop said they replaced it, and it didn't appear replaced, yet the issue went away. Also I am puzzled why the shop can't do anything because of the 'throttle body'.

Lately I have just been shoved (my own choice I suppose) in to the OBD 1.5 pool, so I have been paying extra close attention lately whenever it comes up.
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Old 03-31-2015, 11:03 PM   #6
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What do you recommend for a scanner?

The shop is an "old school" shop in the Atlanta area, with good reputation on Google and lots of "senior" GM cars to work on. I think they know what they are doing - when they want to. But I think they just didn't have time to chase down the difficult stuff for $100.

When I picked up the car last time, the CEL light was off for about 2 minutes and then came back on. I told the owner and he said, the throttle body was worn and needed to be shimmed which makes no sense. He said the only way to fix it, was to replace the throttle body. This doesn't make sense and I think he was trying to get rid of me.
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Old 04-01-2015, 08:32 PM   #7
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I have a 1994 Buick Le Sabre with the same 16 pin connector with the OBD1 system. I can tell you from my experience that the Actron CP9145 scanner will connect and read trouble codes and operating info. It requires the OBDII cable, which usually comes with this scanner, and nothing more.
I would hold off buying a new TPS until a scanner can be located. This can be checked with the scanner for proper operation, and also for adjustment if needed.

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Old 04-01-2015, 10:15 PM   #8
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Quote:
Originally Posted by joeld View Post
I have a 1994 Buick Le Sabre with the same 16 pin connector with the OBD1 system. I can tell you from my experience that the Actron CP9145 scanner will connect and read trouble codes and operating info. It requires the OBDII cable, which usually comes with this scanner, and nothing more. I would hold off buying a new TPS until a scanner can be located. This can be checked with the scanner for proper operation, and also for adjustment if needed. Joel
Joel,

Thank you for your help.

I bought an OEM TPS this morning for $40. I'll see it works out and post my results. I wish I could just rent a scanner. I hate to buy an expensive scanner knowing my daughter will probably sell this car sometime this year.

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Old 04-01-2015, 10:41 PM   #9
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FYI....I test the TPS slightly differently.......With key on, engine not running, Disconnect TPS harness, use voltmeter to measure input voltage and ground....should be 5.0 volts....re-attach the harness and pierce the output signal wire(DK blue?) about 6-7 inches way from the harness...measure that voltage to a good ground.....should be around 0.46 volts closed throttle and increase linearly to 4.7 volts at wide open throttle....the reason why I say to pierce the wire 6-7 inches awayb, is because wires tend to break within 2 inches of the end of the harness...
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Old 04-01-2015, 10:50 PM   #10
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Quote:
Originally Posted by Tech II View Post
FYI....I test the TPS slightly differently.......With key on, engine not running, Disconnect TPS harness, use voltmeter to measure input voltage and ground....should be 5.0 volts....re-attach the harness and pierce the output signal wire(DK blue?) about 6-7 inches way from the harness...measure that voltage to a good ground.....should be around 0.46 volts closed throttle and increase linearly to 4.7 volts at wide open throttle....the reason why I say to pierce the wire 6-7 inches awayb, is because wires tend to break within 2 inches of the end of the harness...
Thank you sir.

That is exactly what I did when I tested the TPS the first time. I did get 5 volts input, but I only got 0.1 - 0.2 volts output no matter the throttle position. I did pierce the wire several inches from the TPS.

I hate to throw parts at it, but I am hoping the TPS is the problem.
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