redindian

I put my 89 on my Snap on mt 2500 scanner and when fully warm in 89*

freeway traffic the scanner reads 145*f - 168*f. at the ECT.

The dash gauge shows 185 - 210*f when ECT value is at 168*f at the most.

I know the dash guage sender is at the back of the head where temps. are greater and the ECT sensor is on the block on radiator inlet side I think.

Will the lower temp. readings richen up the fuel?

Or does the ECU just use the MAT sensor data after engine reaches full operating temp.?

salad

Lower temp could be a result of running rich. Sounds suspicious. Likely that one of the two 25 year old sensors have failed. Have you verified the actual temperature with an IR thermometer?

cruiser54

On my DRB, the CTS reading mimics the dash gauge reading.

The ground circuit for the CTS, IAT, MAP is notorious for being poor.

Ever refreshed your grounds?

Here's how to test the sensor ground circuit:

Cruiser’s Renix Sensor Ground Test
　
This sensor ground circuit affects the CTS, TPS, IAT, MAP, ECU and diagnostic connector grounds. It’s very important and not something to overlook in diagnosing your Renix Jeep as it is common for the harnesses to have poor crimps causing poor grounds. If any or all of the sensors do not have a good ground, the signal the ECU receives from these sensors is inaccurate.
Set your meter to measure Ohms. Be sure the key is in the OFF position. Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS . The letters are embossed on the connector itself.
Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too.
You want to see as close to 0 ohms of resistance as possible. And when wiggling the harnesses/connectors the resistance value should stay low. If there is a variance in the values when wiggling the wires, you have a poor crimp/connection in the wiring harness or a poor ground at the engine dipstick tube stud. On 87 and 88 models, you could have a poor connection at the C101 connector as well.
Revised 06/12/2012

Batman33165

I run probably 180... its a lil lower than half way... and that's streets and highway...