Surging. Which Sensors? Or Worse?
CF Veteran
Joined: Nov 2015
Posts: 2,856
Likes: 201
From: syracuse ny
Year: 1997
Model: Grand Cherokee (ZJ)
Engine: 4.0, new lifters valve job with new springs and exhaust valves, preload set with shims
junk yard is great go pull a map, tps, iac, cts, swap em in cheap to see which is your prob. haha
a scan tool would have shown if the tps was changing % at idle.
Actually I am no fan of just changing parts, but if I had to guess, assuming your ignition is good, (and thats assuming a lot) this is a IAC motor problem.
a scan tool would have shown if the tps was changing % at idle.
Actually I am no fan of just changing parts, but if I had to guess, assuming your ignition is good, (and thats assuming a lot) this is a IAC motor problem.
Last edited by 97grand4.0; Feb 25, 2017 at 01:29 PM.
Thread Starter
CF Veteran
Joined: Feb 2016
Posts: 3,683
Likes: 8
From: Northern New Mexico
Year: 1999
Model: Cherokee
Engine: 4.0
So I'm going about this issue REALLY SLOWLY haha. Just don't have the time between school and work. But I did clean the nss as I saw in other threads like this. It wasn't dirty, but had some hard yellow, wax looking stuff in it. Seems to have made the issue better. It only does it intermittentenvy during the initial warmup period of the jeep. Once warmed up, the problem doesn't act up. So idk hahah maybe a bad nss.
Seasoned Member
Joined: Apr 2014
Posts: 494
Likes: 4
From: Ohio
Year: 98
Model: Cherokee(XJ)
Engine: 4.0L
Mine does something similar -
Upon starting the jeep, about half of the time usually within a couple minutes of starting, the motor will start to run roughly, and the idle may drop down to the low 100's, then rev up to about 1000 or so, then slowly sink back down. it does this for about a minute and almost dies, before it revs up a final time and then runs perfectly fine. if you are driving while this happens, its like the motor bogs down and if you give it more gas, it will accelerate after grumbling and backfiring, then slow down, repeat, ect until it is done.
Does this sound somewhat similar to your issues? it seems almost like the mixture it off in the fuel, somewhat corroborated by the one time it threw a code, it was for the o2 sensor heater circuit. this might be my problem, and it might also be causing yours.
Im still going to check the IAC and clean it out though
Upon starting the jeep, about half of the time usually within a couple minutes of starting, the motor will start to run roughly, and the idle may drop down to the low 100's, then rev up to about 1000 or so, then slowly sink back down. it does this for about a minute and almost dies, before it revs up a final time and then runs perfectly fine. if you are driving while this happens, its like the motor bogs down and if you give it more gas, it will accelerate after grumbling and backfiring, then slow down, repeat, ect until it is done.
Does this sound somewhat similar to your issues? it seems almost like the mixture it off in the fuel, somewhat corroborated by the one time it threw a code, it was for the o2 sensor heater circuit. this might be my problem, and it might also be causing yours.
Im still going to check the IAC and clean it out though
Thread Starter
CF Veteran
Joined: Feb 2016
Posts: 3,683
Likes: 8
From: Northern New Mexico
Year: 1999
Model: Cherokee
Engine: 4.0
Mine does something similar -
Upon starting the jeep, about half of the time usually within a couple minutes of starting, the motor will start to run roughly, and the idle may drop down to the low 100's, then rev up to about 1000 or so, then slowly sink back down. it does this for about a minute and almost dies, before it revs up a final time and then runs perfectly fine. if you are driving while this happens, its like the motor bogs down and if you give it more gas, it will accelerate after grumbling and backfiring, then slow down, repeat, ect until it is done.
Does this sound somewhat similar to your issues? it seems almost like the mixture it off in the fuel, somewhat corroborated by the one time it threw a code, it was for the o2 sensor heater circuit. this might be my problem, and it might also be causing yours.
Im still going to check the IAC and clean it out though
Upon starting the jeep, about half of the time usually within a couple minutes of starting, the motor will start to run roughly, and the idle may drop down to the low 100's, then rev up to about 1000 or so, then slowly sink back down. it does this for about a minute and almost dies, before it revs up a final time and then runs perfectly fine. if you are driving while this happens, its like the motor bogs down and if you give it more gas, it will accelerate after grumbling and backfiring, then slow down, repeat, ect until it is done.
Does this sound somewhat similar to your issues? it seems almost like the mixture it off in the fuel, somewhat corroborated by the one time it threw a code, it was for the o2 sensor heater circuit. this might be my problem, and it might also be causing yours.
Im still going to check the IAC and clean it out though
Newbie
Joined: Nov 2016
Posts: 12
Likes: 0
Model: Cherokee
Surging idle/bucking at acceleration
Mine does something similar -
Upon starting the jeep, about half of the time usually within a couple minutes of starting, the motor will start to run roughly, and the idle may drop down to the low 100's, then rev up to about 1000 or so, then slowly sink back down. it does this for about a minute and almost dies, before it revs up a final time and then runs perfectly fine. if you are driving while this happens, its like the motor bogs down and if you give it more gas, it will accelerate after grumbling and backfiring, then slow down, repeat, ect until it is done.
Does this sound somewhat similar to your issues? it seems almost like the mixture it off in the fuel, somewhat corroborated by the one time it threw a code, it was for the o2 sensor heater circuit. this might be my problem, and it might also be causing yours.
Im still going to check the IAC and clean it out though
Upon starting the jeep, about half of the time usually within a couple minutes of starting, the motor will start to run roughly, and the idle may drop down to the low 100's, then rev up to about 1000 or so, then slowly sink back down. it does this for about a minute and almost dies, before it revs up a final time and then runs perfectly fine. if you are driving while this happens, its like the motor bogs down and if you give it more gas, it will accelerate after grumbling and backfiring, then slow down, repeat, ect until it is done.
Does this sound somewhat similar to your issues? it seems almost like the mixture it off in the fuel, somewhat corroborated by the one time it threw a code, it was for the o2 sensor heater circuit. this might be my problem, and it might also be causing yours.
Im still going to check the IAC and clean it out though
my 91 xj 4.0 5 speed bucks and sputters at acceleration and has a surging idle....I believe the surging idle is a vacuum leak ..but anyway I changed the fuel pump/filter/plugs/tps/cps...02 sensor is next...I hope it does the trick.