Printable Version of Topic

Click here to view this topic in its original format

914World.com _ 914World Garage _ CHT? Car runs great until warm

Posted by: hi4head Jul 2 2006, 04:42 PM

Hi folks,

My '73 2.0 starts and runs fine until it is warm. Then it really starts running rough. If I kick up the rpm's, it seems to help some, but not much.

I've pulled a couple of plugs and they are somewhat sooty.

I've disconnected the Temp Sensor II (CHT). When I connect my multimeter to the connector and touch ground, I get zero ohms. From what I've read, I was thinking that this should read 2000 - 3000 ohms when cold (albeit it is around 80 degrees in my garage). The sensor's connecting wire does not appear to be touching anything.

If the sensor is bad, would this contribute to the car running rich?

Thanks,

Chris

Posted by: brownaar Jul 2 2006, 04:48 PM

Mine did the same thing. My problem was the CHT had worked loose in the head, so it either didn't heat up appropriately or had a bad ground by being loose. Car ran fine cold, like crap when heated up. Was your CHT snug?

Posted by: Brad Roberts Jul 2 2006, 04:50 PM

Do you have the 270ohm resister in place?

B

Posted by: hi4head Jul 2 2006, 07:40 PM

I'll have to check on both points.

I managed to get a deep socket down past the tin and had the connecting wire snake out through the hole. It felt tight, but with only using my fingers in the tight quarters I'm not sure.

As far as the resistor, is that visible? Is it located in-line with the connecting wire, or down at the sensor itself?

Chris

Posted by: Qarl Jul 2 2006, 07:48 PM

Runs great when cold... poorly when warm....

Did you install it backwards?

Just kidding!

Posted by: Brad Roberts Jul 2 2006, 08:20 PM

The resistor is easily visible inline with the harness and head temp sensor.

This typically adds fuel to the system. Basically it fools the system into thinking the engine is cold.

B

Posted by: hi4head Jul 3 2006, 09:10 PM

Since I really don't know fully what I'm doing, I figured that I'd take a picture.

The sensor feels like it is seated tightly. I continue to measure zero ohms when testing from the lead's connector to ground. And when I disconnect the wires shown in the photo while the car is running, the engine stops dead.

First, am I connected to the correct wire? It is in the harness just after fuel injectors #3 and #4.

Thanks,

Chris
Attached Image

Posted by: jk76.914 Jul 3 2006, 09:23 PM

I don't see the 270 ohm resistor. It's supposed to be the first thing that the wire from the CHT sensor plugs into, and then the other end of the resistor plugs into the harness. It looks like your CHT is plugged directly into the harness. The resistor is cylindrical, about 2 inches long. Mine is green, with 270 ohm printed on it in white. Sorry no pictures.....