01 xj misfire problems/ cant run interstate for prolonged periods

redneckjeep87

redneckjeep87

Landscaper Extroidanaire
Joined
Oct 10, 2007
Location
Woodleaf, NC
Before anyone says it, yes i have searched far and wide on this topic.
01 xj 184k on clock
have replaced coil pack, tps, and fuel pump.

I replaced the fuel pump when we got it with a bosch due to pump being bad. Then replaced the coil pack due to bad misfire problems. Everything was hunky dory for quite a while after that. Recently have been fighting a rough idle/ misfire and cannot get rid of it. I replaced the tps due to some reading online stating that they can cause some crazy problems, but no difference. When running the interstate for 7-10miles it starts misfiring BAD almost to the point you cant continue to drive it. Major loss of power almost like it is overheating but gauge reads normal right there at 210. The electric fan works as i testedit sitting in the driveway, left it running for awhile and fan came on. When sitting idling for an extended time it does pop the cel for misfire and almost acts like its loading up sort of like an over carbed engine will sitti g at idle. Any ideas? Could really use some help with this thing. Im fixin to do a compression test today to try and rule out a seeping head gasket.
 
Pull your fuel rail with the injectors attached. Pressurize the fuel rail. Wait to see if one drips. If no drips: remove rail/injector assembly from vehicle. Pressurize with fuel? Then actuate the injects one at a time with wires and battery. Look to see if one sprays more fuel or has a much different spray pattern.
 
redneckjeep87 said:
Before anyone says it, yes i have searched far and wide on this topic.
01 xj 184k on clock
have replaced coil pack, tps, and fuel pump.

I replaced the fuel pump when we got it with a bosch due to pump being bad. Then replaced the coil pack due to bad misfire problems. Everything was hunky dory for quite a while after that. Recently have been fighting a rough idle/ misfire and cannot get rid of it. I replaced the tps due to some reading online stating that they can cause some crazy problems, but no difference. When running the interstate for 7-10miles it starts misfiring BAD almost to the point you cant continue to drive it. Major loss of power almost like it is overheating but gauge reads normal right there at 210. The electric fan works as i testedit sitting in the driveway, left it running for awhile and fan came on. When sitting idling for an extended time it does pop the cel for misfire and almost acts like its loading up sort of like an over carbed engine will sitti g at idle. Any ideas? Could really use some help with this thing. Im fixin to do a compression test today to try and rule out a seeping head gasket.
Click to expand...
Sometimes it's cheaper to find a good shop.
What did your compression test show?
Considering the coil pack fixed your issue initially it might be worth while to verify there's no carbon tracks or indication of the spark jumping. Test the coils for proper operation as well. What are the fuel trims or O2's looking like while the issue occurs?
 
So far compression test has given me cylinders 1-6 respectively 150 179 161 161 180 185. Spec is supposed to be 120-150. I assume the head has been off and decked at some point to give the higher readings? I got those readings multiple times. Put oil in cylinders 1 3 and 4 and got 155 165 and 167, not a big jump to indicate majorly worn rings but a jump nonetheless.


fordwheelinman said:
Pull your fuel rail with the injectors attached. Pressurize the fuel rail. Wait to see if one drips. If no drips: remove rail/injector assembly from vehicle. Pressurize with fuel? Then actuate the injects one at a time with wires and battery. Look to see if one sprays more fuel or has a much different spray pattern.
Click to expand...

Fuel pressure at rail is 47 psi with spec being 46-51. No leaks from pressurized rail/injectors, left it for 15 min. Fixin to test injectors now.

mysterync said:
Sometimes it's cheaper to find a good shop.
What did your compression test show?
Considering the coil pack fixed your issue initially it might be worth while to verify there's no carbon tracks or indication of the spark jumping. Test the coils for proper operation as well. What are the fuel trims or O2's looking like while the issue occurs?
Click to expand...

Couldnt tell you the fuel trims or o2s at the moment, one of my buddys with a big macdaddy solus is 30 or so min away and the other is in charleston for the weekend. Guess its time to come off the hip and buy a scanner. What would be correct way to test the coilpack?
 
Just did individual tests on pressurized injectors. All shot steady stream about 6' not much misting from them. All seemed to be about the same amount of fuel with a little misting off the the side here and there.
 
Got deeper and deeper into this thing today. It has several worn rocker arms and is a sludgey mess. Was in the process of cleaning up the mating surface when i found a small amount of bright ass green coolant on the head bolt inbetween cyl 3 and 4 with a small streak just to the right of it going down the exhaust side casting under the rocker arm to cyl 3. Very minor cracked head with more than likely gummed up lifters and pushrods. So time to find a decent head and have it worked over.
 
redneckjeep87 said:
So far compression test has given me cylinders 1-6 respectively 150 179 161 161 180 185. Spec is supposed to be 120-150. I assume the head has been off and decked at some point to give the higher readings? I got those readings multiple times. Put oil in cylinders 1 3 and 4 and got 155 165 and 167, not a big jump to indicate majorly worn rings but a jump nonetheless.




Fuel pressure at rail is 47 psi with spec being 46-51. No leaks from pressurized rail/injectors, left it for 15 min. Fixin to test injectors now.



Couldnt tell you the fuel trims or o2s at the moment, one of my buddys with a big macdaddy solus is 30 or so min away and the other is in charleston for the weekend. Guess its time to come off the hip and buy a scanner. What would be correct way to test the coilpack?
Click to expand...
To answer there's many ways to skin a cat but I use a DSO. Didn't you say the issue was intermittent?
 
redneckjeep87 said:
So far compression test has given me cylinders 1-6 respectively 150 179 161 161 180 185. Spec is supposed to be 120-150. I assume the head has been off and decked at some point to give the higher readings? I got those readings multiple times. Put oil in cylinders 1 3 and 4 and got 155 165 and 167, not a big jump to indicate majorly worn rings but a jump nonetheless.
Click to expand...


I wouldn't sweat over the compression being "high". The bigger deal to me is the variation. 10% between highest and lowest is usually thrown around as a good baseline. 150-179 side by side would raise an eye brow for me.
 
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