LSxaaron8800

I checked the tps sensor for resistance and i was getting 4.2 ohms.

I tore the harness apart and it already had the sensor connections clipped and soldered together???

also the battery ground is ran to the dipstick tube stud..

edit: 1989 cherokee 4.0

cruiser54

Did you do this?

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.

Refreshing of the dipstick tube connection is covered in Tip #1, and the sensor ground upgrade is covered in Tip #6.

On 87 and 88 models, you could have a poor connection at the C101 connector as well. See Tip #2 and Tip # 27.

Revised 11/01/2014

LSxaaron8800

Yup, cleaned everything. When i tore the loom apart all the brown and white wires were soldered together already...

Jeep stalls when you put the trans in gear and just gently touch the throttle, it sputters and dies.. if you mash the pedal it takes off like normal (spinning wheels)

blows black smoke when you rev engine.

adjusted tps
vac was 16 in.
fuel press 31 and 39 with vacuum line off

map sensor?
02 sensor?
Temp sensor?

cruiser54

But you've got 4 ohms of resistance in the TPS ground circuit using my test?

Did you adjust the TPS using the Engine or trans side? And which method did you use?

Black smoke indicates a possible vacuum issue to the MAP.

LSxaaron8800

i rechecked it with a different multimeter and it was at .3 ohm at the TPS. so thats good


When i adjusted the TPS i took (inputx17%) = (.83volts)

cruiser54

On the flat 3 wire connector, right?

LSxaaron8800

yup.

cruiser54

What elevation are you at?

What do the spark plugs look like?

LSxaaron8800

400ft

they are fouled

cruiser54

MAP sensor and/or it's vacuum supply are highly suspect.

What brand plugs?

How are the cap, rotor, and wires?

LSxaaron8800

new cap was installed when i first got the jeep with a no start condition.

i think the plugs were autolites.

i try to run ngk in everything i have. what do you recommend

plugs wires look fine from a visual inspection

cruiser54

I love NGKs.

Keep in mind that plugs, cap and rotor were to be replaced every 30,000 miles.

Wires were every 60,000.

At the dealership, we just did wires also at 30,000 because we found out they failed before 60,000 quite frequently. High underhood temps in Arizona? Who knows?

LSxaaron8800

I will check vacuum at the map sensor and replace the map

ill get plugs and wires and go from there.

**** I looked on oreillys website and it shows two different vacuum setups. which one is the right one?

cruiser54

The tube from the throttle body to MAP sensor is no longer available.

You have to get creative.

LSxaaron8800

could old gas be causing this? when i bought it the jeep had been sitting for about a year or longer.. i have only put about two half tanks thru it. i dont let it get too empty because the gauge doesn't work right