No, I haven't tested the CTS yet. I just unplugged it on a hunch, which caused the jeep to run better. What I don't understand is this. It's about 30 here in KC. Pretty cold. The jeep is running rich which means my CTS has to read cold *if bad* Can you run a cold engine too rich?

 

Good question. Remember RCBRC?

 

Already took a fresh thing of sand paper out there to re touch up all of my grounds :-).

 

Check out the CTS connector. Pig-rich reaks of MAP sensor problems also. No holes, kinks, melted spots, cracks in MAP hose?

 

Nope. I even pulled the vacuum line at the back of the manifold. Added a t and ran a new vacuum line to the map with the same result.

 

Try unplugging just the IAT and see what happens.

 

Like I said in the earlier post I had the exact same conditions as you. I ohmed out and checked every sensor on the engine. I also ohmed out all the wires to the ecm. The engine would run but was extremely rich and when I reved it up it would rev but never stop at idle and just stall. I pulled the connector off the map sensor also and it would run better for a couple of seconds and then stall. I finnaly decided it had to be a bad map sensor so I disconnected it at the firewall and pulled the vacuum hose out of the throttle body. As I was walking in the garage I flipped the map sensor over and saw a very small hole in the vacuum line where it connects to the map sensor. I did a u turn and put the map back in, repaired the hose, cranked it up and it ran like new.

 

Good possibility you're on to something. Worth looking into.

 

Alright. I pulled the IAT, and the idle dropped. Seemed to be some very slight popping sounds at the muffler too. I mean very slight. The Jeep runs great with the CTS unplugged. Plugged in, it misses bad and shoots out black smoke *pig rich*. The map is brand new, and the vacuum hose is in great shape. I did as Akita said and gave her a good look around. I'm going to hook up the good old volt meter to the CTS tomorrow when it's warmer out. Another point of interest. CTS plugged in and a cold start yields a horrible idle. CTS plugged in and a hot start yields a no start condition. Unplugged, the Jeep will start all day. On the hot no start, you can smell fuel under the hood *no fuel leaks at all*

 

Is it an 87 or an 88?

Oh, just thinking. Running rich and not the Map....

http://www.naxja.org/forum/showthrea...ht=sensor+test


I plan to test my O2 as I'm working to get from 15-16 MPG back to the 18 ish I once had.

Couple odds and ends here too https://www.cherokeeforum.com/f51/he...ix-links-1397/

 

Did more testing this morning. It's 31 here in KC. I ohmed the CTS and IAT both were about 9000 before I started up the jeep. Around 9000 at 31 degrees seems normal. Hooked everything up and started the Jeep. Bad bad idle, and missing. Disconnect the CTS, good idle. Connect the CTS and disconnect the IAT sensor, even worse idle to the point of dying. I take the vacuum hose off the map and give it a good look around *about 5 min worth* No holes. Then *since part of the line is rubber hose* I take some pliers and clamp off the Map hose while the jeep is running. The Jeep wants to die. The jeep is now up to 140 give or take a few temp wise. I shut the jeep off. My IAT reads about 1600, and the CTS reads about 700. Granted I know air cools off quicker than liquid. I then probe the connector that plugs into the CTS. Turn the key to on and I get about 4.8 volts. Should I go out and buy a new CTS? I'm kind of sketchy on if it's bad or not.

 

if it seems to be the only anomaly in the system and all roads go there change it. do you have anyone you could get one off of to check yours against theirs. Up outside of cameron there is an old amc renault dealership on the south side of town. He has got about 20 old renix and maybe 15 more going to 99 mods. parts are cheap. if you ever find your way up there its worth checking out.

 

Resistance chart for both Coolant Temperature Sensor
-and-
Manifold Air Temperature
Coolant Temperature and Manifold Air Temperature Sensor Resistance Values
Approximate resistance your meter should show at the temperature shown in the chart.
NO resistance indicates a 'short' to ground - can be the sensor but will usually be a wire where the insulation has been abraded.
INFINITE resistance indicates an 'open / broken circuit. Can either be a broken wire or a bad sensor.
Degrees Fahrenheit Degrees Celcius Resistance in Ohms
-40 -40 100,700
0 -18 25,000
20 -7 13,500
40 4 7,500
70 20 3,400
100 38 1,600
160 70 450
212 100 185

Wonder if anyone ever rigged up an old O2 plug to a variable resistor/pot.

 

Well, to bring up an old thread. I just replaced the coolant temp sensor. The jeep runs fantastic now. I had no idea a cts * that was testing out fine* could cause it to run pig rich. Learn something new everyday.

 

Fantastic! Thanks much for getting back. Too many posters just walk away! You said it just suddenly went out over night, and that the replacement (presumably) test's the same as the original. I hope if it was just something getting bumped while you installed it, it got bumped really good. Once again, hat's off to Cruiser.