Alright so i have a nice long list of symptoms for you guys. First off 1997 Jeep cherokee, 4.0 HO, aw4, np231, 151,000mi.

So for the past few months, ive been battling what i think is heat soak. So far i have
replaced cracked header
installed hood vents
703 dodge neon injectors
relocated air temp sensor
aux fan switch
plugs, wires, cap and button are 5 months old

So all of the things i have done have helped my heat soak, but havent cured it. Heres everything that it does.

1. If i drive for any reasonable length of time, shut it off, come back in 5-10 min and start it, i get the typical heat soak rough idle. Usually smooths out after a few min or if i rev it good a few times. 3 or 4 times it has stalled and wouldent start. I let it sit with the hood up for 10 or so min, and then fires up with no problem.

2. While im wheeling and not moving alot, it will idle rough. And if im on an obstacle or whatever and try to give it gas, it will missfire and backfire. Usually i can put it in neutral, rev it to 2,500rpm for 5-10 seconds, and everything is fine untill i get off the obstacle and it idles for a min or so. And it is much worse when i have the ac on.

3. If i pin the throddle, it missfires and backfires for a 4-5 seconds and then smooths out but still doesent give me all the power. If i let off the gas a little, the power kicks in and accelerates like it should.

I think i have heat soak, but i think something else is going on also. Im open to any opinions and options. Im sick of dealing with this and want to figure out what it is.

 

Double check that plugs, wires, cap, rotor are correct parts for the vehicle(champion copper plugs) and installed and routed correctly.

Check fuel pressure and volume.

It sounds to me like you may have something in the exhaust causing a restriction at certain times that revving or bumping.around fixes for a while.

Double check your basics first. It doesnt sound like a heat soak issue, that is predominately 00-up 4.0l's.

 

I am currently having almost the exact same issues with my 96. One thing that helped a little for me was replacing my upstream02 sensor. But there still more to be done

 

The o2 sensor has been replaced too. Forgot to mention that one.

The plugs are the champion coppers. I dont believe its related to the plugs, wires cap or button because it has progressevly gotten worse and dident start after i replaced all of those.


Ill check the pressure and volume next.


And i know theres nothing in the exhaust restricting it. Cat has been replaced and i have a after market muffler that is almost a strait pipe.

 

Do BOTH o2's at the same time! Always worth it! If one was bad, the others probably close behind. What about this- is airbag light on and/or does your horn work? Sometime the issue can be traced to the clock spring. It is a grounding point for the TPS.
I suggest this because it looks like you've run the list of standard fixes- plugs/wires, cap/rotor, etc..

 

Without any knowledge, or want to discuss this , maybe check your cat.

 

The down stream o2 doesn't effect fuel trims though. It only serves to monitor the cats efficiency.

And no airbag light and horn works.

 

Didn't know that about bank2 sensor being for cat.. Thanks!

 

No problem. Anyone else got some ideas?

 

Bank 2 is not for cat, its for fuel trims. Sensor 2 is for cats.

Pre-99 dont have a bank 2 sensor, Only 2 sensors. B1S1 & B1S2

Post-99 have bank 2, a total of 4 sensors. B1S1, B1S2, B2S1, & B2S2

 

Thanks man! No sense in questioning your wisdom. I'm gonna do what I can to remember all this..

 

To the top!

 

Feel better?

 

Hmmm...load related backfiring and loss of power.. any vacuum leaks? Agreed on checking fuel pressure ASAP.

 

Nom vac leaks last time a checked. Ill go through em again though.

It werid because if i accelerate lightly, it runs fine. But if i try to get after it, it has a b**** fit. lol