Trouble passing smog test!

[MJRemi]

My 88 4.0 5spd 2wd can't seem to pass smog. The tech says he replaced the O2 sensor and now it's running super rich. He tested the temp sensor and it's fine. I replaced the MAP about 2 weeks ago. He says he thinks it's going to be a bad computer. Since he has my truck for at least another day, can you guys think of any other causes for the rich fuel? Is the computer something I can pull from a JY or should I buy a new one? This is getting frustrating and expensive.

[Mongo]

can't say for sure, but usually a rich fuel mixture is due to a temperature sensor, but not sure that our computer monitors that. I will have to dig in the factory manual later on this evening to see. Other thing to check fuel pressure for a leaking fuel injector. I will see if there is anything when I get done with my honeydo and post up.

[alleydog]

Maybe the fuel pressure regulator is leaking. pull the vacuum hose off it an see if theres fuel in it.

[shelbyluvv]

Check the EGR valve too. If it is sticking it will make it run like crap.

[MJRemi]

Hopefully I will get my truck back from the shop on Thursday. The owner/mechanic seems to know what to test but i don't think the MJ is a priority for him. I really need to learn how to do this work for myself. The labor and mark-up costs are killing me. I'll be glad to get this smogged so I can move on to the transmission swap.