Hi there ...

My 1984 Recaro TA is just idling really bad. I have the 3rd carburetor now installed, second one was cheap aftermarket, didn't work at all. Now I got an overhauled original Rochester wich is doing good, but not great. Nearly no cold idle, hot idle is very rough. Guess the ECU is giving wrong values to the carb. Also is my Check Engine on, saying some tempsensor. Replaced them all. No change

Now, even though I wanted to keep the car original, I'm coming more an more to the point, where I'm asking myself if swapping the E-Rochester with a normal Edelbrock, no electronics will sove my issue. Conmpression test done, al cylinders between 150-170psi

Thanks for any advice.

Regards,

Ernest

 

The only temp sensor that the ECM knows anything about, is the one in the water outlet, where the upper radiator hose connects.

It expects that no matter what temp is sees when the engine is first started, after a few minutes the temp will come up to some reasonable value; say, 60°C within 10 minutes, or something like that, I don't recall the exact numbers. If it doesn't see the temp do that, then it assumes there's a sensor problem. The sensor being unplugged for example, will make the ECM see -40°C all the time, which is clearly wrong; it'll give you a code for that. Likewise, if the sensor itself is shorted or the wires are touching each other, it thinks the temp is like 175°C or some such, which is equally clearly wrong, at an initial startup. The ECM doesn't have any way of knowing "the sensor is bad"; just, it's a physical thing reacting to physical conditions in the physical world, which act in predictable physical ways, and if it sees the world acting impossibly stupid somehow through the only "eyes" it has, which is that sensor, then it assumes that there must be a sensor problem, and lights the light & sets a code.

Your car came originally with a sort of round coaxial looking connector on that sensor, that was wrapped in some kind of gummy black tape. The connector is total GARBAGE, and the gooey glop in the tape EATS the insulation off the wires. They ALWAYS fail. The wires can touch each other and give the extreme high temp failure, and the connector is crappy and doesn't make a good connection, so sometimes it is essentially unplugged and the ECM sees Antarctica. Sometimes both happen at the same time and it changes from one to the other when you hit a bump as you drive along. Very confusing to 70s electronics no doubt.

Replace that sensor. It has a yellow and a black wire. Replacement ones have an oval connector with 2 wires. Many of them come with a new pigtail in the box. https://www.rockauto.com/en/moreinfo...Lf4%2FpA%3D%3D for example. Get one like that, cut back the old wire with the insulation that's crumbled to dust far enough to get to undamaged wire, and splice the new in with solder and heat shrink tubing. DO NOT use those blue Scotchlock connectors that come with it.

Forget "Edelbrock". Repair what you have.

 

Someone else recently posted about this. https://www.thirdgen.org/forums/cool...ng-sensor.html Same as yours.

 

I replaced that sensor. Had to change the wiring, because it got ground on the engine block. The new ons as 2 wires. One for the signal and the second for ground.

 

It's supposed to have 2 wires, like the pic from the other post. Wiring it wrong may be the problem with it.