Odd 3SFE Electrical Problem

[lionheart03]

Have a recently overhauled 91 Camry with a 3SFE. If you refer to my old posts, you'll read that I had a burnt valve, which is now fixed. I have another problem that has been a PITA to fix.

Here is what happens. While driving the car, when the transmission downshifts to speed up, if the engine RPM's are high enough, the temp gauge begins to jump up, not slowly, but a fast jump that moves with revving the motor. When it does this, the car begins to miss badly, and will die if you don't give it gas until the thing seems to even back out, that is the motor begins running smoothly again.

I don't have a tach, but this is what I observed at idle. Revving the motor, maybe around 3K RPM, the temp gauge rises and falls a bit, at normal running temp. When I do this the motor starts to miss, so I have to give it a little gas, or it will die. When the motor does die, it will not fire when you crank it. Starting fluid gets it going and running fine again, with the temp gauge back to normal. When it started to miss at idle, I gave it quite a bit of gas, and the temp gauge kept rising up almost to max, but when I let off the gas, it falls back down.

A simple check on the motor verifies that all plugs and connectors are making good connections.

If the car sits for a while, it will start normally again. I disconnected the battery, in case it may be a CPU issue. Any other ideas?

Thanks for any and all help!

[Doctor J]

The temperature sender and injector control transistors in ECU are sharing common ground point [bolt] on the underside of intake manifold.I have not investigated the issue if the gauge can show overheating if the ground brown wire is disconnected from the sender [it may indicate "cold" instead but I would suggest to check the wires at this ground point to make sure they are not twisted or torn or dirty
{Provided that engine IS NOT overheating!!}

[lionheart03]

Doc J, once again you have shown your great wisdom! I said I had checked every connection and cable. Well, all of them but the one causing the problems. Felt behind the intake manifold, and there is was. I must have missed this when I was putting everything back together.

Connected the ground, and the problems are all gone, car running perfectly fine.

Once again, thank you!

[Doctor J]

I wish I would find easy solution for my jumping tach!!