Date: Wed, 11 Feb 1998 22:30:31 -1000 (HST) From: Alan H S Chung Subject: Re: Still stalling... Heya bob and all Well here are some of your numbers. Do you have a good multimeter? you'll need to at least measure voltage and OHMs here. Not ohm, but OHMS. yeha that funny looking horse shaped thing...ah well...here goes, right from the service manual Usually all the sensors you need to check, you'll have to stick the voltmeter probes in the back of it or break the back of it while they are still hooked up. That is pretty easy, but thin leads will help.
Coolant sensor.Depending on temp, it should range from 100,700 (100.7K) Ohms at -40 degree F to 185 Ohms at 212 degree F. 100 degree F will be 1600 ohm and 160 degree F will be 450 ohm. It's worth checking this because the CPS and Coolant sensor must work in conjunction to make the 4.0L run.
MAP sensor testA is ground, B is output voltage and C is 5 volts. With ign swicth on, engine off, A+B should equal 4-5 volts. Start engine and run till warm/hot. The voltage should drop to 1.5-2.1 volts with hot neutral idle. Also test A+C, should be 5 volts +/- .5 Volts.
Crank position sensor test...With engine off, A+B should equal 200 +/- 75 ohms with hot engine. also when measuring voltage, volts should spike when engine is cranked or is running. If no reading, CPS is bad. Oops, disconnect sensor when doing ohm test...
O2 sensor test...Disconnect and measure A+B. should be betwen 5 and 7 ohms. if infinity reading, replace sensor.
Mass Temp sensor test...disconnect harness and measure two wires resistance. should be less than 1000 ohms with warm engine. Also there is maybe two other checks...make sure the knock sensor is snug and all the wiring is intact. Also checking the ignition module, the plug farthest forward...Front to rear they are C tach signal, B ground, and A ignition. A bad ground here can cause your problem you describe. There is even a saying of it in the diagnosis, bad voltage here can result in low speed miss. Also check the stator and all the distributor parts. Well, hope this helps some and no you can search. BTW, ABC are labelled on the back of the all the connectors, so you don't mix them up. Bob, let me know if you have any other questions. Sometimes if you can't get a good voltage reading TO the sensor, there may be a break in the wiring form the engine computer, whci is even more headaches. Anything else? Well, good luck and ttyl Mahalo Alan Chung 90 Cherokee Limited Honolulu, HI ------------------------------ to john's how to install the Crank Position Sensor
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