Stalling/running rough: Diagnostic Challenges
01-19-2017, 01:11 AM
#1
CF Veteran
Thread Starter
Stalling/running rough: Diagnostic Challenges
Back from the other side of the world to get input from the US.
Back with a vengeance...
Apologies for the little read, but thought to prevent a long list of “ have you tried this already” by giving some background info on the issuer at hand.
After some years of relative minor issues with the XJ, an old enemy has now returned: the intermittent stalling/ bucking/ running rough. It used to do it occasionally when driving, engine cold or warm, but now has been there pretty much constant, rendering the XJ useless to drive.
Some history: Had these symptoms started several years back. The below repairs the past 4-5 years seemed to have cured the issue each time (for a prolonged time). Never had any Check Engine light come on during any of these, the light itself is working, no codes on my scanner , except one, see further down )
Replaced MAP sensor and cleaned throttle body
(together with a tune-up with new plugs, wires, distributor cap and rotor)
Replaced Crankshaft position sensor (CPS)
Replaced CAM shaft sensor
New battery (2x)
New Cath converter about 4 years ago
O2 sensors are still on the shelves, I just can’t get the old bastards out, tried too many times. However, one could drive without O2 sensors, it should give a rich ride, but it shouldn’t cause the stalling, bucking and rough idle/running I’d say. The smell of a very rich running engine is keeping me accompanied when in the engine bay and it idles like a dragster racer.
So, hating to think one of the already replaced sensors failed on me already, I thought to look into other possible causes, thinking that something intermittent like this is likely more an electric/sensor issue. The past days I’ve spent testing:
TPS: voltage ranging from 1.5V at closed throttle to 3.96V at WOT which seems to be within specs
Smooth needle movements up and down on the analogue multimeter, no dead spots or hesitation. Tapping on the TPS or wiggling the wires didn’t influence this at all.
CPS: measuring continuity over pin B and C gives infinite resistance, not indicating a short
(the old CPS would give the same actually, indicating it wasn’t faulty?? However after changing it out, the issue disappeared for about 2-3 years!!!)
MAP sensor: gets 5,12 V power, has good ground, and signal wire reads 4.7V key on/engine off, and idle shows the signal wire giving around 1.9-2.3 Volt. Not sure if this is somewhat high. Opening the throttle drops the voltage (as it should be)
After disconnecting the MAP sensor while the engine was running, to see if this made a difference (maybe a little but its idling so crap at the moment it was hard to tell) , the CHECK ENGINE light came on, giving code p0108 (MAP/Barometric pressure circuit high). I guess this is because I disconnected it?
Pulled the plugwires one by one, all cylinders seem to be working (slight increase in rough idle when pulled)
I like to think it is going to be something simple like a sensor. But so far they pretty much test good (although not sure about that relative high signal Voltage of the MAP at idle)
Starting to get to the end of what I can think of or test. Maybe an intermittent coil issue (although I’d expect no starts or shutting down). But what was initially intermittent stalling while driving, has now progressed to something more permanent with rough idle, and rough running.
In short: I can use your input and questions and I’m open for any ideas/thoughts! I think by now I know more about this XJ than a mechanic in a shop here would or would care about to diagnose (no offence) and I don’t feel like paying someone who is just going to replace parts till its fixed, IF it gets fixed that way.
Cheers in advance.
Back with a vengeance...
Apologies for the little read, but thought to prevent a long list of “ have you tried this already” by giving some background info on the issuer at hand.
After some years of relative minor issues with the XJ, an old enemy has now returned: the intermittent stalling/ bucking/ running rough. It used to do it occasionally when driving, engine cold or warm, but now has been there pretty much constant, rendering the XJ useless to drive.
Some history: Had these symptoms started several years back. The below repairs the past 4-5 years seemed to have cured the issue each time (for a prolonged time). Never had any Check Engine light come on during any of these, the light itself is working, no codes on my scanner , except one, see further down )
Replaced MAP sensor and cleaned throttle body
(together with a tune-up with new plugs, wires, distributor cap and rotor)
Replaced Crankshaft position sensor (CPS)
Replaced CAM shaft sensor
New battery (2x)
New Cath converter about 4 years ago
O2 sensors are still on the shelves, I just can’t get the old bastards out, tried too many times. However, one could drive without O2 sensors, it should give a rich ride, but it shouldn’t cause the stalling, bucking and rough idle/running I’d say. The smell of a very rich running engine is keeping me accompanied when in the engine bay and it idles like a dragster racer.
So, hating to think one of the already replaced sensors failed on me already, I thought to look into other possible causes, thinking that something intermittent like this is likely more an electric/sensor issue. The past days I’ve spent testing:
TPS: voltage ranging from 1.5V at closed throttle to 3.96V at WOT which seems to be within specs
Smooth needle movements up and down on the analogue multimeter, no dead spots or hesitation. Tapping on the TPS or wiggling the wires didn’t influence this at all.
CPS: measuring continuity over pin B and C gives infinite resistance, not indicating a short
(the old CPS would give the same actually, indicating it wasn’t faulty?? However after changing it out, the issue disappeared for about 2-3 years!!!)
MAP sensor: gets 5,12 V power, has good ground, and signal wire reads 4.7V key on/engine off, and idle shows the signal wire giving around 1.9-2.3 Volt. Not sure if this is somewhat high. Opening the throttle drops the voltage (as it should be)
After disconnecting the MAP sensor while the engine was running, to see if this made a difference (maybe a little but its idling so crap at the moment it was hard to tell) , the CHECK ENGINE light came on, giving code p0108 (MAP/Barometric pressure circuit high). I guess this is because I disconnected it?
Pulled the plugwires one by one, all cylinders seem to be working (slight increase in rough idle when pulled)
I like to think it is going to be something simple like a sensor. But so far they pretty much test good (although not sure about that relative high signal Voltage of the MAP at idle)
Starting to get to the end of what I can think of or test. Maybe an intermittent coil issue (although I’d expect no starts or shutting down). But what was initially intermittent stalling while driving, has now progressed to something more permanent with rough idle, and rough running.
In short: I can use your input and questions and I’m open for any ideas/thoughts! I think by now I know more about this XJ than a mechanic in a shop here would or would care about to diagnose (no offence) and I don’t feel like paying someone who is just going to replace parts till its fixed, IF it gets fixed that way.
Cheers in advance.
01-19-2017, 07:05 AM
#2
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,867
Received 1,524 Likes
on
1,236 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Back from the other side of the world to get input from the US.
Back with a vengeance...
Apologies for the little read, but thought to prevent a long list of “ have you tried this already” by giving some background info on the issuer at hand.
After some years of relative minor issues with the XJ, an old enemy has now returned: the intermittent stalling/ bucking/ running rough. It used to do it occasionally when driving, engine cold or warm, but now has been there pretty much constant, rendering the XJ useless to drive.
Some history: Had these symptoms started several years back. The below repairs the past 4-5 years seemed to have cured the issue each time (for a prolonged time). Never had any Check Engine light come on during any of these, the light itself is working, no codes on my scanner , except one, see further down )
Replaced MAP sensor and cleaned throttle body
(together with a tune-up with new plugs, wires, distributor cap and rotor)
Replaced Crankshaft position sensor (CPS)
Replaced CAM shaft sensor
New battery (2x)
New Cath converter about 4 years ago
O2 sensors are still on the shelves, I just can’t get the old bastards out, tried too many times. However, one could drive without O2 sensors, it should give a rich ride, but it shouldn’t cause the stalling, bucking and rough idle/running I’d say. The smell of a very rich running engine is keeping me accompanied when in the engine bay and it idles like a dragster racer.
So, hating to think one of the already replaced sensors failed on me already, I thought to look into other possible causes, thinking that something intermittent like this is likely more an electric/sensor issue. The past days I’ve spent testing:
TPS: voltage ranging from 1.5V at closed throttle to 3.96V at WOT which seems to be within specs
Smooth needle movements up and down on the analogue multimeter, no dead spots or hesitation. Tapping on the TPS or wiggling the wires didn’t influence this at all.
CPS: measuring continuity over pin B and C gives infinite resistance, not indicating a short
(the old CPS would give the same actually, indicating it wasn’t faulty?? However after changing it out, the issue disappeared for about 2-3 years!!!)
MAP sensor: gets 5,12 V power, has good ground, and signal wire reads 4.7V key on/engine off, and idle shows the signal wire giving around 1.9-2.3 Volt. Not sure if this is somewhat high. Opening the throttle drops the voltage (as it should be)
After disconnecting the MAP sensor while the engine was running, to see if this made a difference (maybe a little but its idling so crap at the moment it was hard to tell) , the CHECK ENGINE light came on, giving code p0108 (MAP/Barometric pressure circuit high). I guess this is because I disconnected it?
Pulled the plugwires one by one, all cylinders seem to be working (slight increase in rough idle when pulled)
I like to think it is going to be something simple like a sensor. But so far they pretty much test good (although not sure about that relative high signal Voltage of the MAP at idle)
Starting to get to the end of what I can think of or test. Maybe an intermittent coil issue (although I’d expect no starts or shutting down). But what was initially intermittent stalling while driving, has now progressed to something more permanent with rough idle, and rough running.
In short: I can use your input and questions and I’m open for any ideas/thoughts! I think by now I know more about this XJ than a mechanic in a shop here would or would care about to diagnose (no offence) and I don’t feel like paying someone who is just going to replace parts till its fixed, IF it gets fixed that way.
Cheers in advance.
Back with a vengeance...
Apologies for the little read, but thought to prevent a long list of “ have you tried this already” by giving some background info on the issuer at hand.
After some years of relative minor issues with the XJ, an old enemy has now returned: the intermittent stalling/ bucking/ running rough. It used to do it occasionally when driving, engine cold or warm, but now has been there pretty much constant, rendering the XJ useless to drive.
Some history: Had these symptoms started several years back. The below repairs the past 4-5 years seemed to have cured the issue each time (for a prolonged time). Never had any Check Engine light come on during any of these, the light itself is working, no codes on my scanner , except one, see further down )
Replaced MAP sensor and cleaned throttle body
(together with a tune-up with new plugs, wires, distributor cap and rotor)
Replaced Crankshaft position sensor (CPS)
Replaced CAM shaft sensor
New battery (2x)
New Cath converter about 4 years ago
O2 sensors are still on the shelves, I just can’t get the old bastards out, tried too many times. However, one could drive without O2 sensors, it should give a rich ride, but it shouldn’t cause the stalling, bucking and rough idle/running I’d say. The smell of a very rich running engine is keeping me accompanied when in the engine bay and it idles like a dragster racer.
So, hating to think one of the already replaced sensors failed on me already, I thought to look into other possible causes, thinking that something intermittent like this is likely more an electric/sensor issue. The past days I’ve spent testing:
TPS: voltage ranging from 1.5V at closed throttle to 3.96V at WOT which seems to be within specs
Smooth needle movements up and down on the analogue multimeter, no dead spots or hesitation. Tapping on the TPS or wiggling the wires didn’t influence this at all.
CPS: measuring continuity over pin B and C gives infinite resistance, not indicating a short
(the old CPS would give the same actually, indicating it wasn’t faulty?? However after changing it out, the issue disappeared for about 2-3 years!!!)
MAP sensor: gets 5,12 V power, has good ground, and signal wire reads 4.7V key on/engine off, and idle shows the signal wire giving around 1.9-2.3 Volt. Not sure if this is somewhat high. Opening the throttle drops the voltage (as it should be)
After disconnecting the MAP sensor while the engine was running, to see if this made a difference (maybe a little but its idling so crap at the moment it was hard to tell) , the CHECK ENGINE light came on, giving code p0108 (MAP/Barometric pressure circuit high). I guess this is because I disconnected it?
Pulled the plugwires one by one, all cylinders seem to be working (slight increase in rough idle when pulled)
I like to think it is going to be something simple like a sensor. But so far they pretty much test good (although not sure about that relative high signal Voltage of the MAP at idle)
Starting to get to the end of what I can think of or test. Maybe an intermittent coil issue (although I’d expect no starts or shutting down). But what was initially intermittent stalling while driving, has now progressed to something more permanent with rough idle, and rough running.
In short: I can use your input and questions and I’m open for any ideas/thoughts! I think by now I know more about this XJ than a mechanic in a shop here would or would care about to diagnose (no offence) and I don’t feel like paying someone who is just going to replace parts till its fixed, IF it gets fixed that way.
Cheers in advance.
Test your MAP sensor.
01-19-2017, 07:11 AM
#3
CF Veteran
Join Date: Aug 2010
Location: Canton, MI
Posts: 8,357
Likes: 0
Received 82 Likes
on
67 Posts
Year: 1999
Model: Cherokee
Engine: 4.0
Some testing data:
Recommend using a safety pin as a back probe if you don't have a professional back probe(s).
TPS tests:
MAP Sensor tests:
.
Idle -
.
Ignition Coil tests:
Remove coil to do the tests and inspect the coil.
Cracked coil -
.
~~~~~~~~~~~~~~~~
Using an Ohmmeter, check the resistance of each fuel injector.
Pin to pin, the injector should read about 11 Ohms at room temp.
~~~~~~~~~~~~~~~~
If you don't have one, see if you can get a scanner that shows live data. Watch the O2S activity and Short Term Fuel Trim.
Replace your O2S' anyway. Use NTK O2S'.
Recommend using a safety pin as a back probe if you don't have a professional back probe(s).
TPS tests:
MAP Sensor tests:
.
Idle -
.
Ignition Coil tests:
Remove coil to do the tests and inspect the coil.
Cracked coil -
.
~~~~~~~~~~~~~~~~
Using an Ohmmeter, check the resistance of each fuel injector.
Pin to pin, the injector should read about 11 Ohms at room temp.
~~~~~~~~~~~~~~~~
If you don't have one, see if you can get a scanner that shows live data. Watch the O2S activity and Short Term Fuel Trim.
Replace your O2S' anyway. Use NTK O2S'.
Last edited by CCKen; 01-20-2017 at 05:42 AM.
01-19-2017, 06:04 PM
#4
CF Veteran
Thread Starter
Gentlemen, good to see you're still here.
tested the coil and injectors, all with their specs.
tested the MAP again and had about 2.1V at ie on the signal wire. 'Snapping' the throttle I did yesterday as well, seeing it go up to 3.33V and today when I did this I saw a 4.64V briefly on the meter, and that wasn't even WOT. Isn't that a somewhat high voltage?
It idles like a Chevy Trailblazer and increasing the RPMS makes that sound the same, till I go over 1250 RPMS, then it starts to sound like an XJ again.
(Yesterday I've made pics of the scanner including the O2 sensors, I'll try and post them later)
Could it be the MAP sensor still?
tested the coil and injectors, all with their specs.
tested the MAP again and had about 2.1V at ie on the signal wire. 'Snapping' the throttle I did yesterday as well, seeing it go up to 3.33V and today when I did this I saw a 4.64V briefly on the meter, and that wasn't even WOT. Isn't that a somewhat high voltage?
It idles like a Chevy Trailblazer and increasing the RPMS makes that sound the same, till I go over 1250 RPMS, then it starts to sound like an XJ again.
(Yesterday I've made pics of the scanner including the O2 sensors, I'll try and post them later)
Could it be the MAP sensor still?
Trending Topics
01-19-2017, 08:25 PM
#8
CF Veteran
I may be way off target here, no insults intended... but the plug wires are in the right order?
What type of plugs did you use? Everyone says certain types are junk. Always wondered why. Can they be crappy straight outta the box?
What type of plugs did you use? Everyone says certain types are junk. Always wondered why. Can they be crappy straight outta the box?
01-21-2017, 06:43 AM
#9
CF Veteran
Thread Starter
Plugs are OEM Champions and yes, wires are in firing order.
So, thanks to a mate, I could swap in some spare parts to test.
Changing the MAP and TPS didn't make any difference. Will try coil as well, but I don't think it's the cause.
It starts fine, but idles like a heavy Chevy Trailblazer or something like that,and smells very rich. Increasing the RPMS gives the same sound butndriving it is shaky and obvious loss of power.
Further input?
So, thanks to a mate, I could swap in some spare parts to test.
Changing the MAP and TPS didn't make any difference. Will try coil as well, but I don't think it's the cause.
It starts fine, but idles like a heavy Chevy Trailblazer or something like that,and smells very rich. Increasing the RPMS gives the same sound butndriving it is shaky and obvious loss of power.
Further input?
01-21-2017, 01:02 PM
#10
CF Veteran
Join Date: Nov 2010
Location: In the middle of Minnesota!
Posts: 5,804
Received 99 Likes
on
88 Posts
Year: 1999
Model: Cherokee
Engine: 4.0
Have you tested your fuel pressure to see if it is in spec? If not, that's on your list! For a 97, you're looking for 49 psi, plus or minus 5 psi.
Last edited by tjwalker; 01-21-2017 at 01:08 PM.
01-22-2017, 12:23 AM
#11
CF Veteran
Thread Starter
No, haven't yet (need to buy a pressure gauge, we can't rent stuff here like you guys; ) )
Have been doing the poor man's prime for ages, so maybe the fuel pump assembly finally fell over.
Have been doing the poor man's prime for ages, so maybe the fuel pump assembly finally fell over.
01-22-2017, 04:13 AM
#12
CF Veteran
Join Date: Aug 2011
Location: Nor-Cal Coast
Posts: 10,489
Likes: 0
Received 17 Likes
on
17 Posts
Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
Sorry you don't have a Renix. If I waz a neutrino, could I see the soles of you feet? 
Sorry to hear from you since that means you are having trouble. Floored, the map still matters plenty, but most of the other, don't. (TPS must matter). Floored it likely will ignore the O2 and temp sensors, others also I'd guess. What..speed sensor and IAT..Idk. (oh! you can try unplugging the IAT...wont matter but easy enough to try)(Likewise the temp sender(s)
You are positive the MAP tube is flawless.
I don't understand your four wire Zerconia 02 sensor, it's different. Our three wire Titania (variable resistance for the 5v Feed from the puter"), might freak out the puter if that was grounded. Does it go good if you floor it? (really floorboard it) Have you, "A" verified the forward 02 sensor wires are not grounding anywhere, and "B" tried it with the 02 unplugged?
Both easy things to check I think. Also Freedgr mentioned if you cut the wires you can put a 7/8 box wrench right on the 02. I bought a $16 can of Kroil last year btw.
Really works and a dab will do you.
I'll sleep on it, (right-side up of course)
Sorry to hear from you since that means you are having trouble. Floored, the map still matters plenty, but most of the other, don't. (TPS must matter). Floored it likely will ignore the O2 and temp sensors, others also I'd guess. What..speed sensor and IAT..Idk. (oh! you can try unplugging the IAT...wont matter but easy enough to try)(Likewise the temp sender(s)
You are positive the MAP tube is flawless.
I don't understand your four wire Zerconia 02 sensor, it's different. Our three wire Titania (variable resistance for the 5v Feed from the puter"), might freak out the puter if that was grounded. Does it go good if you floor it? (really floorboard it) Have you, "A" verified the forward 02 sensor wires are not grounding anywhere, and "B" tried it with the 02 unplugged?
Both easy things to check I think. Also Freedgr mentioned if you cut the wires you can put a 7/8 box wrench right on the 02. I bought a $16 can of Kroil last year btw.
Really works and a dab will do you. I'll sleep on it, (right-side up of course)