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Confusing TPS Problems
Topic Started: Apr 17 2011, 11:08 PM (3,478 Views)
Wobblybob


It's fixed! Idle at about 900 rpm. ISC installed and working. Just like it's supposed to.

As usual, mwebb was right. So was Johnny Mullet. And others too.

I just had to get all the pieces of the puzzle and mull them over for a while.

More later . Have to run right now but thanks again to all,
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Johnny Mullet
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Fear the Mullet

Sweet! Let us know what it was.
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Johnny Mullet
Apr 22 2011, 11:54 AM
Sweet! Let us know what it was.
^o) :thumb :coffee
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Wobblybob


Not so fast Bob!

I spoke too soon. I still don't have any DFCO. I'm trying to figure that out but I'm visiting family for the holiday weekend and can't find the time to think it through.

I was able to reinstall the ISC motor and it appears to be working fine. I realized that the cycling idle problem started when I first used the .14" feeler gauges to set the TPS (on the improperly adjusted idle set screw). That's how it was set when I took the car to JM's (with the ISC motor disconnected).

I haven't reasoned this thru completely but it occurred to me that the .14" setting demands that the ISC open the throttle from the idle stop screw to achieve the 1.0 volt signal that the PCM is looking for. But the engine was idling fine with the throttle against the stop. Maybe one signal (the TPS) is, in effect, telling the ISC to advance the throttle and once it does some other sensor (?) is telling the ISC to retard the throttle. In any event, I reasoned that the TPS voltage should be 1.0 volts when the engine is idling (like mwebb says). So I checked it yesterday morning and it was 0.46 volts! So I reset the TPS to 1.0 volts, no feeler gauge, key on, engine off. Then, just to satisfy my curiosity I checked it again with engine running (no change from engine off).

Then I plugged in the ISC and no cycling. I thought all was good but on my way to Pittsburgh I realized that the DFCO was not working. Looking through my notes I see that the DFCO has never worked when I used mwebb's method for setting the TPS.

So it's not back to square one by any means, but we haven't crossed the finish line either.

More later after the weekend.

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Wobblybob


Good news, bad news.

Good news is I made some TPS and idle stop screw changes and the car is running just like it should. Idles between 800 & 1000, ISC seems to be doing it's job and I have DFCO every time!

Bad news is I really don't understand why it's working now and wouldn't work at JM's the other night.

The TPS is set 1/16" clockwise of where it was and the idle stop screw is less than 1/4 turn from where it was. Runs fine now and cycled endlessly between 1100 and 2000 the other night.

Also, the TPS is set where it started 6 days ago. The only thing changed since then is the idle stop screw. Now it idles fine and DFCO works every time - six days ago it idled at 1100 to 1200 and DFCO only worked occasionally.

I would really like to make sense out of this so I know what to do if it happens again. The lower idle and reliable DFCO have to make a big difference in mpg's, especially in stop and go situations.

If anyone can offer any theories or insight to what happened here, please speak up.

Thanks.
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