Black Plumes and Rough Idle
#1
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Year: 1993
Model: Cherokee
Engine: 4.0 HO
Black Plumes and Rough Idle
Fellas, I’m kinda stumped on an ongoing issue with my ‘93 XJ project. So as a pretense this is a freshly rebuilt engine and upgraded to four hole Bosch injectors (part # 0280155758).
Any recommendations or opinions would be greatly appreciated. The Jeep has never had working A/C so I decided to replace the system. Basically everything besides the evaporator core. In the process I disconnected and removed the battery for more room to work with but whenever I reconnected the battery to charge the system I noticed the engine running extremely rich and flooding out the cylinders. Whenever I accelerate plumes of black smoke come out of the exhaust . The engine idles sporadically, almost like the computer is trying to adjust the fuel. So far I’ve replaced the MAP sensor (NTK), O2 sensor (NTK), and got a new battery but to no avail. I even cleaned all the grounds hoping maybe it was sensor signaling issue. I took it to my local mechanic and he concluded it was bad gas or bad PCM which I don’t believe is the issue. I’m thinking maybe the upgraded injectors might be sticking open but the mechanic said they were signaling fine. Before throwing parts at it I wanted to see if anyone had any suggestions. Thanks
Any recommendations or opinions would be greatly appreciated. The Jeep has never had working A/C so I decided to replace the system. Basically everything besides the evaporator core. In the process I disconnected and removed the battery for more room to work with but whenever I reconnected the battery to charge the system I noticed the engine running extremely rich and flooding out the cylinders. Whenever I accelerate plumes of black smoke come out of the exhaust . The engine idles sporadically, almost like the computer is trying to adjust the fuel. So far I’ve replaced the MAP sensor (NTK), O2 sensor (NTK), and got a new battery but to no avail. I even cleaned all the grounds hoping maybe it was sensor signaling issue. I took it to my local mechanic and he concluded it was bad gas or bad PCM which I don’t believe is the issue. I’m thinking maybe the upgraded injectors might be sticking open but the mechanic said they were signaling fine. Before throwing parts at it I wanted to see if anyone had any suggestions. Thanks
#2
CF Veteran
Fellas, I’m kinda stumped on an ongoing issue with my ‘93 XJ project. So as a pretense this is a freshly rebuilt engine and upgraded to four hole Bosch injectors (part # 0280155758).
Any recommendations or opinions would be greatly appreciated. The Jeep has never had working A/C so I decided to replace the system. Basically everything besides the evaporator core. In the process I disconnected and removed the battery for more room to work with but whenever I reconnected the battery to charge the system I noticed the engine running extremely rich and flooding out the cylinders. Whenever I accelerate plumes of black smoke come out of the exhaust . The engine idles sporadically, almost like the computer is trying to adjust the fuel. So far I’ve replaced the MAP sensor (NTK), O2 sensor (NTK), and got a new battery but to no avail. I even cleaned all the grounds hoping maybe it was sensor signaling issue. I took it to my local mechanic and he concluded it was bad gas or bad PCM which I don’t believe is the issue. I’m thinking maybe the upgraded injectors might be sticking open but the mechanic said they were signaling fine. Before throwing parts at it I wanted to see if anyone had any suggestions. Thanks
Any recommendations or opinions would be greatly appreciated. The Jeep has never had working A/C so I decided to replace the system. Basically everything besides the evaporator core. In the process I disconnected and removed the battery for more room to work with but whenever I reconnected the battery to charge the system I noticed the engine running extremely rich and flooding out the cylinders. Whenever I accelerate plumes of black smoke come out of the exhaust . The engine idles sporadically, almost like the computer is trying to adjust the fuel. So far I’ve replaced the MAP sensor (NTK), O2 sensor (NTK), and got a new battery but to no avail. I even cleaned all the grounds hoping maybe it was sensor signaling issue. I took it to my local mechanic and he concluded it was bad gas or bad PCM which I don’t believe is the issue. I’m thinking maybe the upgraded injectors might be sticking open but the mechanic said they were signaling fine. Before throwing parts at it I wanted to see if anyone had any suggestions. Thanks
I assume there was no problem before you did the AC work, correct? charging the AC and removal and reinstall of battery likely wont effect engine running unless some electric component was dislodged during that work.
Was the injectors upgraded at same time as AC charging? did these injectors work ok before, or never before?
maybe put original injectors back in?
Does exhaust smell rich?
If catalyst equiped, dont drive while rich running, else catalyst maybe ruined$$$$$$$$$$.
good luck
#3
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Year: 1993
Model: Cherokee
Engine: 4.0 HO
Remove the spark plugs, compare them, see if some show signs of rich running. a stuck open injector will reveal itself with a gasoline soaked plug, sooty appeance. once the bad plug is found, you can then test that injector for being stuck open.
I assume there was no problem before you did the AC work, correct? charging the AC and removal and reinstall of battery likely wont effect engine running unless some electric component was dislodged during that work.
Was the injectors upgraded at same time as AC charging? did these injectors work ok before, or never before?
maybe put original injectors back in?
Does exhaust smell rich?
If catalyst equiped, dont drive while rich running, else catalyst maybe ruined$$$$$$$$$$.
good luck
I assume there was no problem before you did the AC work, correct? charging the AC and removal and reinstall of battery likely wont effect engine running unless some electric component was dislodged during that work.
Was the injectors upgraded at same time as AC charging? did these injectors work ok before, or never before?
maybe put original injectors back in?
Does exhaust smell rich?
If catalyst equiped, dont drive while rich running, else catalyst maybe ruined$$$$$$$$$$.
good luck
#4
CF Veteran
Could you confirm the part numbers of those injectors...having a hard time finding them on google search..they will be on side of the injectors
#5
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Year: 1989
Model: Comanche (MJ)
Engine: 4.0
Part number translates to 20 lb/hr 16-ohm injectors.
https://motorwestperformance.com/fue...tes-and-specs/ (look under top feed)
Seems close enough to replace the stock 21 lb/hr injectors
http://www.jeep4.0performance.4mg.com/tech_specs.html
https://motorwestperformance.com/fue...tes-and-specs/ (look under top feed)
Seems close enough to replace the stock 21 lb/hr injectors
http://www.jeep4.0performance.4mg.com/tech_specs.html
#6
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Year: 1993
Model: Cherokee
Engine: 4.0 HO
Part number translates to 20 lb/hr 16-ohm injectors.
https://motorwestperformance.com/fue...tes-and-specs/ (look under top feed)
Seems close enough to replace the stock 21 lb/hr injectors
http://www.jeep4.0performance.4mg.com/tech_specs.html
https://motorwestperformance.com/fue...tes-and-specs/ (look under top feed)
Seems close enough to replace the stock 21 lb/hr injectors
http://www.jeep4.0performance.4mg.com/tech_specs.html
#7
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
My money is on the tube/hose to the MAP sensor being clogged, melted, split or loose fitting.
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#8
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Year: 1993
Model: Cherokee
Engine: 4.0 HO
Tested all injectors with multimeter. All injectors read 16.1 - 16.4 ohms which i believe is spec for this injector. Pulled the plugs, all were fouled up pretty bad. I cleaned them up with a wire brush and checked the gaps. Cylinders 3, 5, 6 were gapped around .25. Cylinder 4 was gapped around .40…I cleaned them up and gapped all plugs to spec .35 and reinstalled. Noticed a dramatic difference in idle and engine performance. And best of all no more excessive black fumes coming from exhaust when hitting the throttle. Could incorrect gap plug cause engine to run so rich?
#9
Senior Member
If the plug gaps on your "freshly rebuilt engine" were that messed up I gotta wonder what else is off. You are assuming the fouled plugs and smoke and rough running are from running rich, could be misfire .
For starters were the rotor,cap, and coli&plug wires replaced?
For starters were the rotor,cap, and coli&plug wires replaced?
#10
CF Veteran
First....040 down to .035 will not fix anything unless your coil is garbage, and even then not likely. Those injector part numbers look like 0280155759 to me...those are 30 lb injectors Every plug there is running super rich. You have the wrong injectors
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lawsoncl (11-02-2022)
#11
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Year: 1993
Model: Cherokee
Engine: 4.0 HO
If the plug gaps on your "freshly rebuilt engine" were that messed up I gotta wonder what else is off. You are assuming the fouled plugs and smoke and rough running are from running rich, could be misfire .
For starters were the rotor,cap, and coli&plug wires replaced?
For starters were the rotor,cap, and coli&plug wires replaced?
#12
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Year: 1993
Model: Cherokee
Engine: 4.0 HO
Im planning on going to the junkyard this weekend and grabbing some original injectors . I can’t find the ones I originally took out. I bought these Bosch injectors on eBay for $85, which was probably my first mistake. After cleaning up the plugs it’s running a lot better but if the injectors are rated at 30lbs that means it putting more fuel in cylinder than spec and the plugs will foul up again, right?
#13
CF Veteran
Im planning on going to the junkyard this weekend and grabbing some original injectors . I can’t find the ones I originally took out. I bought these Bosch injectors on eBay for $85, which was probably my first mistake. After cleaning up the plugs it’s running a lot better but if the injectors are rated at 30lbs that means it putting more fuel in cylinder than spec and the plugs will foul up again, right?
Correct. The wrong gaps are not bad enough to cause the running issues. But injectors that deliver too much fuel will cause problems.
does she smell rich?
use care, rich running will eventually ruin the catalyst.
#14
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Year: 1993
Model: Cherokee
Engine: 4.0 HO
Yes she's always smelled rich since injector install but its definitely more prominent the more I've driven it. Which makes sense because plugs just kept getting more and more fouled up. I'm going to park it for a few days until I get original injectors back in. Will update when thats complete. Preciate all the help fellas!
Last edited by Wcreech8; 11-02-2022 at 07:33 PM.
#15
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Plugs are never pre-gapped except by us before we install them.
There is someone on Cherokee Forum that provides the correct injectors all refurbished.
There are MANY cheap chinese knock-off injectors out there. Get original rebuilt ones!! trevor.skankfootracing@gmail.com
There is someone on Cherokee Forum that provides the correct injectors all refurbished.
There are MANY cheap chinese knock-off injectors out there. Get original rebuilt ones!! trevor.skankfootracing@gmail.com