Hi i have an 88 Renix 4.0 with 267k. Lately the exhaust smells very rich, also i have a misfire or bucking at a certain throttle level. If i floor it the bucking stops if i let off a little the bucking stops but it seems to buck the most at the throttle level needed to maintain current speed. It does it in all gears no matter what speed im going but i can turn the jeep off and it will sometimes start running perfect again. Also sometimes it worse than other times anyone ever had this problem?

 

Welcome. Please fill out your info. I still haven't nailed that one down. Does it cough, pop back out the intake when you gas it, but go fine if you floor it?

Past 70/80% throttle Renix will ignore a bunch of sensors and just go.
Clean up some basics first. Plugs Gaped to .o35? (and not platinum or something goofy)The dizzy cap is clean inside and out?

Here's Crusiers Tips. Where me, the 2 minute CPS test would be #1, but you could start on 1 through 5. For sure you want to at least clean that C101 connecter, and the grounds. > https://www.cherokeeforum.com/f51/cru...x-tips-153657/

Fuel pressure should be about 39# with the vacuum off the regulator, (front on fuel rail), and about 10 less with the line on. It's free to borrow the tester. You defenantly want to do that.

 

Make sure you check the vacuum line going to the MAP sensor. If it is cracked, loose or damaged you will run rich.



(Image officially stolen from Cruiser54)

 

As well as above mentioned info, Get your multi meter out and test the O2 sensor.

 

Great suggestions here.

 

Brain fart here Pete. Just a couple of months ago, exact thing, (and I had it to with my bad routing)(shield short). Some guy nailed it.What was it? Wanna say fuel pressure, but...couldn't the CTS tell it to run lean, (thinking it's hot hot), until the throttle past 70% tells the ECU to ignore the temp sensor? If it were fuel pressure you'd think it would still mess up at WOT.

Bugs me this keeps coming up and I can't nail it. I DID lay bare the shorting wires on "Brown" and try to duplicate it, couldn't get it to do it grounding a number of suspect wires.