HunterRivett

Hello. I recently purchased a 1998 XJ, 4x4, Automatic, 4.0 I6 with 160000 miles. There is no catalytic converter on it, and only the upstream o2 sensor is on. I am using Autolite plugs. It rarely starts, when it does it starts after the key has come back a little. It idles really rough, and on acceleration, backfires rapidly at 2000 rpms. I have checked power on all gauges, and they all read NO POWER. PCM? I need help in my fixing process. I have ordered a catalytic converter and o2 sensor. I will put them on in a week. After that, what should I check and replace. THANK YOU SO MUCH.

Fred/N0AZZ

Once you have those installed those see what codes your getting then. In the mean time clean all electrical connections from steering column to the PCM along with all sensor connections. Disconnect clean use dielectric grease then reconnect without bending pins but seated solidly.

If you have not done a "complete" tune-up since purchase it might be a good time to consider that also to rule those out.

Crazy 8s

CCKen

Do Not use dielectric grease on any ground connection or in a connector.

Use only on exterior light bulb sockets and spark plug boots.,

CCKen

What do you mean by gauges all read NO POWER?

Fuse #9 in the Junction Block (passenger footwell fuse panel) powers the instrument cluster, fuse #16 in the Power Distribution Center (engine bay) also provides power to the instrument cluster. Fuse #16 is the IOD fuse, identified on the PDC cover.

HunterRivett

When checking sensors, not gauges, sorry.

XJwonders

out of curiosity, how come?

CCKen

Sensors? Like the TPS, MAP, CPS?

You should have 5 volts +/- .5 volts at the connector Orange wire on each of these sensors with the ignition switch to RUN/ON position (without crankng the engne).

HunterRivett

One gauge, the TPS, said 0.4, all others said 0-0.1. No power.

Fred/N0AZZ

Ken I have always used the Dielectric Grease on any connections where water can come into contact with. I'm ashamed to say I have had a few 4x4's in the water up to the dash/over the engine several times in the past that were not greased and they really gave me problems later. Have always used on exterior lighting on about everything I own from the boat trailer to the Diesel Pusher Motor Home.

What problems have I caused by using it on the connectors for everything on my XJ? Have I went too far with a good thing, out thinking myself and ended up shooting myself in the foot

Wouldn't be the first time for sure lol.

SteveMongr

Dielectric grease is non-conductive, it will prevent current flow. When used in an electrical connection such as a multi-pin, it can prevent pin contact unless all of grease on pins is pushed aside upon connecting.

XJwonders

makes sense now

SteveMongr

Conductive grease has the opposite effect and can cause big trouble as well.
If used on a multi-pin, it is done in tiny amounts directly on the pin. The grease can cause current to jump pins if too much is applied.

CCKen

Dielectric grease is an insulator. Used in connectors that have marginal pin/cavity contact the dielectric grease will only serve to agrivate the situation. Same with ground connections; it will insulate the connection. There are conductive products that are specifically used for ground connections, like NOALOX and OX-GARD, but are not to be used in pin connectors.

If you check each connector on your Jeep you will not find dielectric grease in them, nor on the ground connections. You will find it being used on external lamps, like headlights and tail lights on just about all vehcles.

EDIT: As a side bar, a foum member PM'd me to tell me he had read one of my posts about not using dielectric grease on pin connectors. He stated that he had problems with his CPS so he removed the grease and it fixed his problem. Proof of the pudding mates.

CCKen

Hope you are using the 20 VDC scale on your digital voltmeter, and have the ignition switch to the ON/run position.

Generally, if you see low voltage readings on all the 5 volt supply voltage (Orange) sensor wires (like you are seeing) it means the PCM is bad. On the other hand, if you see voltages above the 5 volt +/- .5 volt spec it means the clockspring is bad.