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Hey all.. I have a 1994 Olds Ninety Eight with a... well a 3800 of course! It's naturally aspirated, not lucky enough to get my hands on a S/C one.. well time to get to the point I guess..

The symptoms: itnermittently, the check engine light will come on, I've found this is generally at operating temp, ad the engine seems to be at a loss for power. I have found more recently, in fact, that the transmission is shifting prematurely, so much so that I'll be in 3rd gear before I reach 25 or 40 mph. It doesn't matter then how hard I try to accelerate, it doesn't downshift, just slowly putts along until 3rd gear can finally pull it. A couple times it acted in the exact oposite manner, however. It pulled so hard that I reached 30 mph withhout even touching the accelerator. I checked for vaccum leaks, fixed a couple and the problem still persisted. Intermittently, of course. Once the check engine light comes on, it will stay on, but the symptoms never persist through an entire drive cycle. On the highway the car hiccups but goes right back to normal. It seems to be a phantom electrical problem.

I have an intermittent P0122 code: Throttle Position Sensor Circuit voltage low. So I went through the troubleshooting, checked supply and return voltage on the tps.. Everything checked out fine. (5.01v, supply voltage. Return voltage was at 5.01v open, .46v closed) so from my research, everything is in range. Please correct me if I'm wrong though. Anyway, I ended up essentially ended up ruling out the sensor itself. While testing though, I found the connector keeper tab was broken, so I thought maybe the broken tab was causing the connector to back out a little and in turn causing it to jump voltage and make the return voltage read out of range. So I went to the junkyard and got a connector that was in good shape, and spliced it in. To splice, I removed the loom all the way to the main engine wiring harness to inspect the wires all the way for chaffes or cuts. Found nothing. So I connected the harness with solder and heat shrink tubing to ensure a secure connection. Hooked up everything and reran the loom, tested and the check engine light came on again once the engine reached operating temp. So now here I am, perplexed.

Could it be that the TPS is going out and that's why it's reading ok and still acting up at times? Does this sensor go out gradually or just altogether? Thanks in advance of any help or advise you can give me. As of now, I'm at a loss and I can't really afford throwing parts at it.
 

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I think that 5.01v at wot is a tick high. If my memory serves me correctly, it's usually approx 4.5v. Also, you should try measuring the signal return circut for a nice even increase in voltage from idle to wot. When doing this move the tps very slowly so you can catch any glitches if they are there.

Good luck, Jake L.

ps.... It may be possible for this code to set from the early shift/no down shift condition. Like moderate throttle at 35 mph when it's in high gear an no down shift. Can you access the trans data???
 

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I've seen sensors stick and do flakey things.

If the pcm see's intermittent, then likely it was playing cat and mouse while you tested it and it's heat related so maybe it only acts up when up to temp and heatsoaked.

I'd swap it and most likely it's the only issue.
 

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Discussion Starter #4
Yeah I got a couple TPS' from the junkyard. I'm going to try them tonight and see if we can't get this thing licked. The gas milage is killing me and Im driving 100+ miles to go floating tomorrow so it has to be right. I'll let you guys know how it turns out. Thanks for the help.
 

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Discussion Starter #5
I don't have access to any reader to pull trans data but that's what it's doing isearly shift/no downshift. If that's the case, what do you think in the trans would be the culprit?
 
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