89 2.5 4 speed TBI injected MJ wierd problems

OK here it is gang, I just got my MJ back from my sis inlaw and the battery was cold dead, took about 30 minutes to jump it. I drove it around a tad. Then onthe 210 mile jont back home with it it started acting strange

It would not idle, die each time I let off the accelerator and whne it ran it surged and bucked like staved for fuel. After about 50 miles of this I pulled over a played with it a bit. un hooked the vac line for the MAP sensor and it ran much better! still lacked power.

I got it home last night and this morning put in a new MAP sensor, fired it up and ran fine till it warmed up then it died, unhooked the vac line restarted and it runs ok..........any clue?

How's the oxygen sensor?

Any time I hear "It runs fine until it warms up" I get suspicious. Remember, especially on the Renix (which the TBI system is), open-loop mode bypasses sensor input and runs on a predetermined air/fuel/ignition map (not MAP, map -- as in program). The ECU switches over to closed loop mode when the temperature reaches around 165, at the sensor located in the side of the block.

So if it runs all nicey-nice in open loop mode and screws up in closed loop mode, start looking at sensors. You've tried the MAP sensor and that didn't do it, so perhaps the O2 sensor is next.

Eagle said:

How's the oxygen sensor?

Any time I hear "It runs fine until it warms up" I get suspicious. Remember, especially on the Renix (which the TBI system is), open-loop mode bypasses sensor input and runs on a predetermined air/fuel/ignition map (not MAP, map -- as in program). The ECU switches over to closed loop mode when the temperature reaches around 165, at the sensor located in the side of the block.

So if it runs all nicey-nice in open loop mode and screws up in closed loop mode, start looking at sensors. You've tried the MAP sensor and that didn't do it, so perhaps the O2 sensor is next.

Click to expand...

gotta love the renix over all, Ive got a 4.0 87XJ here which uses the same part # for teh o2 senser, maybe pull it tomorrow and try round 2

Yeah, hurry up and get that thing fixed! :laugh3:

Done yet?? :laugh3:

BillR said:

Done yet?? :laugh3:

Click to expand...

Go sit on your hands somewhere, most impatient person I know..............:laugh3:

BillR said:

Done yet?? :laugh3:

Click to expand...

nope been drawing house plans ....till 3 am last night...still drawing this morning....need more coffee......3 pages to go....... :speepin:

BillR said:

Done yet?? :laugh3:

Click to expand...

Well the 4.0 and 2.5 o2 sensors are different...........no one in northern az even carries them........not even jeep...go figure...........o2 on order...will be here tomorrow......maybe LOL