Strange and horrible sounding '87 Renix 4.0 I6

[matt0106]

I'm going to test the coil and ICM to see if they're good or not. Then I think, the fuel pressure regulator and vacuum lines are next to be checked.

All that sound good to ANYONE on the forum?

[4.3LXJ]

I was thinking you should check the fuel pressure too. Do you have a gauge?

[4.3LXJ]

If it stays at 40 psi, then you don't need to check the regulator. It is fine

[matt0106]

Ok. So what else could be causing my jeep to start but not run for very long? The only things I can think of are related to fuel and spark.

My step dad mentioned an intake manifold leak. Is that possible?

[4.3LXJ]

Get that O2 sensor nailed down yet. If you put one in out of a non running vehicle, I would be suspect of that. Here is how it works. The first few minutes the computer provides a rich mixture. Once the heated O2 sensor is supposedly heated up, then it begins relying on that. It it is not working, then it will not run.

[matt0106]

No, I don't think anyone mentioned checking the O2 sensor. The current one in there is probably pretty old, so it could be bad. Would an exhaust leak cause one to go bad quicker?

[4.3LXJ]

No, but typically it will cause the mixture to become too rich from fresh air getting sucked into the exhaust

[matt0106]

Ok. Is there a way to test the O2 sensor? Or do I just have to flat out replace it?

And I was thinking, that maybe background info as to how this may have happened, might help people understand what's wrong.

[4.3LXJ]

If it hasn't been replaced in a long time, replace it. They wear out and the sensing function cannot be tested

[matt0106]

Ok. Is there a brand I should stay away from? Where should I get it?

Also, thank you for helping me out. The Cherokee veterans over at Cherokee forum are giving me crap for asking suggestions.

[4.3LXJ]

OEM I think is probably the best. I have had good luck with Bosch, but others haven't.

[matt0106]

So if I got a Bosch one at AutoZone, I could return it if I need to?

[4.3LXJ]

I don't think you can do that once installed. Besides, you need to put antisieze on the treads that should come with it. I understand the cost issue, but they really need to be changed every 50K anyway to maintain your fuel economy

[matt0106]

Ok. Because I never replaced it and it can't hurt to replace it. Thanks.

[XJ Wheeler]

A suggestion... I just searched around for my O2 sensor and found Rock Auto to be the cheapest. No, you can't walk in to return/warranty it but the warranties suck anyways and the savings made up for it in my opinion.