New member needs mechanics help

[Jboden615]

1998 XJ 4.0 automatic. Keeps throwing codes at me p0204,p0205 can play with injectors the codes will stop and it will run good but after 5-10 miles codes come back. Not always the same have gotten p0201 and p0203 as well normally not more than 2 codes at a time. So far I replaced all fuel injectors, new tps, had new plugs and wires on it. Also tried replacing the computer from another XJ same year and all but still got the codes. I don’t mind buying parts but this XJ needs a lot so I only want to buy parts I need until its running good. After that I plan to continue to buy and replace parts for reliability. Goal is to have it reliable for my son to drive daily, however I know he likes mud. Any help is greatly appreciate

[downsy]

Check and double check all your grounds, even if they look good take them off clean them then reinstall. Really you could probably benifit from a full battery cable and ground replacement.

Then you need to start troubleshooting the injector harness. Get a multimeter if you dont have one set it to continuity mode and start shooting wires between the injector connections to the PCM, you may need to wiggle parts of the harness while doing this to see if you can replicate a wire break.

Those codes are specifically related to the injector circuit so nothing on the ignition side should be an issue.

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[4.3LXJ]

I agree. Since you have replaced the injectors, it is in that circuit. One other thing, there is a product called OxGuard that really improves the conductivity of all the plug connections. Use it sparingly, apply with a tooth pic since it will bridge the spades if slopped on. It contains grit in it, so plug and unplug several times and will renew the surfaces of the plug

[Jboden615]

Ok did a little testing with volt meter from neutral on battery to each green / orange injector wire with engine running and get 13.9 on all wires. Also used a basic test light with engine running and test light is on and bright to each g/o wire. When I use test light on the other wire I get a dim light that flickers or blinks. I would assume that is firing. Not sure how to do test on the pcm or where and what that is.

[Jboden615]

How would that change with engine off. Can I check continuity with wires and battery?

[4.3LXJ]

Do you actually feel a miss when this happens?

[Jboden615]

Not 100% sure if I could hear it but can feel a difference while driving then check engine light goes on. Got new connectors for the fuel injectors today ( thanks amazon) so I will butt splice them in tonight I hope. Don’t know if that will help or not.

[4.3LXJ]

We had a similar problem with a TJ 4.0. It didn't really affect the drivability, but did throw a CEL. Put a tank of premium gas in it and got rid of the problem as long as we ran it. Passed inspection and then went back to regular and a light

[Jboden615]

It has fresh gas as I just bought it and came empty. When I drive it I can feel a problem like a misfire lack of power and rough.

[4.3LXJ]

Any problems with coolant loss?

[Jboden615]

Not leaking but really have not but any miles on since I bought it. To busy replacing parts to drive it. I have had it less than a month and have installed fuel injectors, full rear brakes with hardware cables and lines, front brakes with new calipers, brake master cylinder, both transmission cooling lines, radiator hoses, tps sensor, new radio and speakers. Tonight cleaning all the different grounds and it looks like the two close to block passengers side will need replacing tomorrow. My plan is to butt splice new #8 wire to some spot on existing wire and add new ring connectors. Think I over payed for this XJ now because it was not rusted but it’s needing more mechanical work than I thought.

[Jboden615]

Also see about 1/2-3/4 of a each of bare copper wires coming out of the ignition coil harness connector. Not sure how to replace the connector or just get some good electrical tape between the wires and then tape them up.

[4.3LXJ]

Next question which I probably know the answer to. How long has the O2 sensor been in there? No one ever changes them until it is too late

[Jboden615]

I have not changed either o2 sensor yet but did repair wiring to the one on drivers side towards front of engine. Should I be replacing them both? How would that help me.

[Jboden615]

With o2 sensor does brand matter local auto zone has Bosch at $52-$62 each but I see other brands on line less than half the price?

[4.3LXJ]

Not sure on brand, but yes you should replace both. They wear out over time and affect the fuel/air mixture. You could be just on the border of being too lean which would cause that miss. One indication would be if you don't have that miss when first started up but it appears after the engine gets warm.

[downsy]

NTK (NGK) manufactured the OEM O2 sensors. General consensus on various forums is to go with them.

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[Jboden615]

Just wanted to say thanks as my cel are off. Not 100% sure how but after replacing the fuel injector connectors and about 8 inches of new wire, cleaning all the grounds.

[downsy]

Good deal electrically gremlins can be a pain

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