XJAnvil99

After reading a few more threads, it seemed that the normal signal from the TPS at idle is about 13-15 %. Mine was at about 10.5, which was just above 9.8 %, the lowest reading I could get with the idle stop screw backed all the way out. With the engine running, I adjusted it to about 13.5%, shut it off, and disconnected the battery to reset the computer again while I double checked all of the fuses.

When I reconnected the battery and tried to start it, there was no fuel pump, no spark, no start. I checked the input voltage for the CPS and Cam Sync Module, and both were getting just over 5 volts. The output pulses of the CPS seemed low (under 2 volts) but were definitely there , while the Cam Sync Module pulses were much stronger, nearly the same as the input voltage.

Double checking all of the fuses, it turns out I put the fuse for the fuel pump, computer, etc., in the wrong slot. With all of the fuses back in the right place, it fired right up, and settled into a decent idle as it warmed up. Once I got it all the way to above 200*, I disconnected the battery one more time to reset the computer.

This time, it idled steady at about 750rpm. After two minutes, I turned the a/c on to max for two minutes, and it still idled right at 750. Putting in drive made no change to the idle speed, and after two more minutes, I drove it for about 30 minutes without any problems.

I let it cool for an hour or so, and it started right up, but idles a little erratically, varying about 200-300rpm, but never dropping below 700rpm or so. Putting it in drive, it immediately settled into a steady 750rpm idle, with the a/c making no change. After that, it idled
normally in park with the a/c off.

It seems ok now, but will see how it does in the morning, since it’s still 108* outside right now. It might want a little more base throttle signal
at idle, but it seems pretty freaking close now.

Eric

Dave51

That's probably OK depending on how you measured it. If you used a plain old DVM, since the signal alternates between 0 and 5.0 volts so rapidly the DVM gives an average. You could either go really slow or use a DVA, but it's probably fine.

XJAnvil99

Which is why I just bumped the engine over several times to watch the voltages as the signal ring goes by the sensor. I did that plenty of times to see peak voltages vs. low voltages. The Cam Sync Sensor was much easier, since it's half on/half off every rotation of the distributor, which turns at half of the crankshaft speed. I have both a digital multimeter, which doesn't seem very old school to me, and an analog multimeter, which definitely DOES seem old school to me. My digital multimeter also has peak hold, so reading the highs and lows is actually quite easy. I apologize for giving you the impression that I didn't know how to use a multimeter, even though I never mentioned anything about that.

Eric

Dave51

In that case, you have a problem.

There's a somewhat more involved way to confirm proper operation (including sync) of CPS/CKS. If problem turns out to still be there have to consider that.

XJAnvil99

Yep, since the peak voltages I saw on the CPS seemed quite low at just below 2 volts, and it still doesn’t run well when cold, and only runs well intermittently when it’s warm, it looks like a failing CPS. I just really hate throwing parts at it, and there is no use in fixing any of the other issues this thing has until it runs properly and reliably. And it has some issues!

XJAnvil99

I replaced the CPS last week, and it helped, but didn't solve the issue. Since I had replaced the TPS before, and it's only been a few thousand miles since then, I was reluctant to replace it again. I decided to look at the CPS signal while driving, since it looked good in the garage, and it was bouncing up and down all over the place. I replaced it again with a "premium" sensor from NAPA (the old one was an "economy" sensor from O'Reilly's), and it read 16.8% with the throttle stop backed all the way out, and about 17.2% with it adjusted to just barely open it from fully closed. After another computer reset, and several trips of 20-30 each, it runs just about flawlessly, starting quick and idling smooth, hot or cold.

Thanks for all the comments and suggestions.

Eric

Roler

Replaced the CPS or TPS again?