Ok, newbie here seeking wisdom from the jeep crowd.

1995 Cherokee Sport, 4.0L. Started with low idle issues, no codes. During troubleshooting, I noticed the MAP vacuum line was broke (I mighta done it!). At some point I started to get the 13 & 14 codes for the MAP. Now, when I start the jeep, it runs rough but idles at about 750 for a minute, then the idle drops, engine light comes on (13 & 14), and it dies. Driving it, I get some backfire when accelerating.

I replaced the IAC & MAP, as well as the broken vacuum line - no change. Also fuel filter, just to make sure it wasn't an issue. Disconnected battery for a bit, too.

I've tested voltage, ground, and variance on the MAP, all's good. Could find no other vacuum issues.

My next thought is fuel pump... any thoughts?

 

Yeah. Test your fuel pressure.

 

No tester available in town, so I went ahead and replaced the fuel pump. New pump, same old issues and codes.

First day delivering rural mail is Saturday, I might have to break down and find a mechanic that'll make a house call.

 

No codes for fuel pump issues.

Check this out:

http://www.allpar.com/fix/codes/faults/code13.html

 

True, no fuel pump codes. The only thing left in the list you linked is fuel pressure regulator, all else tests good or has been replaced. I'll check it out, thanks.

 

Replaced the regulator and checked its vacuum line. There was a slight fuel smell in the vac line, so I was hopeful. Even did the 20 minute drive that people suggest to let the ecm get to know all the new parts (though I've never had that actually make a difference in real life).

But, only a minor change -- MAP sensor codes seem to be a little slower to throw, but still dies when foot's off the gas when I slow below about 10mph, or when idling. Drives smooth at highway speeds, though lacks a little bit of power.

Might be able to limp through Saturday, but my route's 130 miles and 360 mail boxes... not a challenge I would choose.

 

Forgot to mention above, only throwing the 13 code after changing the fuel pressure regulator.

Pulled the exhaust to rule out the catalytic converter -- no change, though the straight 6 didn't sound too bad with straight pipes! Dropping it off at the shop in the morning, hopefully they'll get a chance to look at it before I run the route again Tuesday -- Saturday did NOT go well, 360 stops nursing the gas pedal, and trying to rush the 1/2 mike stretches was painful!

O, and I also ethered around the intake, throttle body, and vacuum lines/outlets to check for a bad seal. No change in rpm, so thats probably not an issue.

 

The shop says broken valve springs. We'll see in a couple days when they do the work. I'll post when I get it back, hopefully without a long list of add-ons.
In the meantime, short-cab S-10's console is removed so I can drive from the right, guess I'll practice on my route tomorrow.

 

That sounds suspicious to me.....

 

Sure does....

 

It is possible they are correct but I would perform a compression and leakdown test myself to verify.

Let us know how it goes.

 

Yeah, I've considered the possibility that they'll show me some broken springs from another job, change a fouled plug and charge me for doing the springs. But, they have a good reputation, have been recommended by others including another shop, and i just don't stinkin' have the time to deal with it myself at this point.

I really appreciate the input. Mechanics and chiropractors -- always be careful to trust them, but if you find a good one they can make your life good.

 

Final verdict: 10 of the 12 valve springs were broken. One was broken in two places, which was the cylinder without compression. They agreed that this is unheard of, maybe a manufacturer defect in the previous batch? -- head was pulled a few months ago, if the springs were replaced then that would mean they didn't have too many miles on them.
It ran great when I got it a month ago, running even better now.

 

Yay. Problem found and an honest shop.

 

X2 and thanks for letting us know.