cnugent
NAXJA Forum User
- Location
- Pacific Northwest
I've seen low fuel pressure cause misfires before. Is your fuel pressure within spec?
-
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Misfire
- Thread starter ottexj2000
- Start date
JNickel101
NAXJA Forum User
- Location
- Alamogordo, NM
Basically this means that the the car's computer has detected that not all of the engine's cylinders are firing properly.
A P0300 OBD DTC code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring. Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why.
Symptoms
Symptoms may include:
A code P0300 may mean that one or more of the following has happened:
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.
Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.
My opinion:
Since you have not replaced the coil pack rail, I would start with that. You seem to be getting random misfire codes on a few different cylinders, so to me, I would replace the item that is connected to ALL of the plugs, and therefore, can affect all cylinders.
A P0300 OBD DTC code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring. Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why.
Symptoms
Symptoms may include:
- the engine may be harder to start
- the engine may stumble / stumble, and/or hesitate
- other symptoms may also be present
A code P0300 may mean that one or more of the following has happened:
- Faulty spark plugs or wires
- Faulty coil (pack)
- Faulty oxygen sensor(s)
- Faulty fuel injector(s)
- Burned exhaust valve
- Faulty catalytic converter(s)
- Stuck/blocked EGR valve / passages
- Faulty camshaft position sensor
- Defective computer
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.
Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.
My opinion:
Since you have not replaced the coil pack rail, I would start with that. You seem to be getting random misfire codes on a few different cylinders, so to me, I would replace the item that is connected to ALL of the plugs, and therefore, can affect all cylinders.
ottexj2000
NAXJA Forum User
- Location
- Guilford, CT
Well, I believe I have fixed my #3 Misfire. I have not checked fuel pressure. I will look into getting a Coil Rail but with that being such an expensive part I am alittle hesitant to condem it. Is there a way for me to test it with my Ohm Meter?
Ron Hyslop
NAXJA Forum User
- Location
- Madison, WI
Remove the heat shield and get a can of Mopar cumbustion chamber cleaner. Spray the whole can of cumbustion cleaner through the throttle body as per instructions on can with one exception. When the can is empty, shut off the engine, and let it soak an hour(soften up carbon deposits). Start the engine, let it idle a couple minutes, then go out and flog it a bit. Leave the transmission in 3rd gear and get the engine rpm above 3000(above 3000 rpm the valves rotate in the seat). Be care full not to get any over spray on the TPS. This was recommended to me by a 30 year Jeep tech, and it cured the missfire problem in my 01 xj. I do it every 50000mi.
winterbeater
NAXJA Forum User
- Location
- Royal Oak, Michigan
I haven't seen any ideas on how to test the coil rail. Use of an alternative coil rail such as a Ford 3 liter has been suggested (Talyn's idea) which are about half the price of the Jeep one, but I would be hesitant to try that if I already had a problem.
ottexj2000
NAXJA Forum User
- Location
- Guilford, CT
UPDATE
Well I think my XJ just hates me. I was in New Hampsire last week and my CEL came on and was flashing. Luckily I was only about 2 miles from my buddies house and he is a Mechanic so we quickly scanned the CEL and it was a Cylinder #1 Misfire. So he consulted his boss a 35 year Tech. His boss took a quick look and said Injector 1 is bad. While I had the Injector out buddy's Boss looked in the Cylinder with a Boreoscope. He said everything looked fine for a Engine with almost 200,000 miles on it. I explained everything I have been going through with this Misfire. He said if the Misfire comes back and is numerous Cylinders, replace the Coil Rail. If a single Cylinder do a Fuel Injector. And to also do some Combustion chamber cleaner. Well 2 days ago CEL back on with 2 Misfire codes. So i ordered a Coil Rail. I pray to God this will fix it becasue I am about to find a older XJ and buy and drive this on off a cliff.
Well I think my XJ just hates me. I was in New Hampsire last week and my CEL came on and was flashing. Luckily I was only about 2 miles from my buddies house and he is a Mechanic so we quickly scanned the CEL and it was a Cylinder #1 Misfire. So he consulted his boss a 35 year Tech. His boss took a quick look and said Injector 1 is bad. While I had the Injector out buddy's Boss looked in the Cylinder with a Boreoscope. He said everything looked fine for a Engine with almost 200,000 miles on it. I explained everything I have been going through with this Misfire. He said if the Misfire comes back and is numerous Cylinders, replace the Coil Rail. If a single Cylinder do a Fuel Injector. And to also do some Combustion chamber cleaner. Well 2 days ago CEL back on with 2 Misfire codes. So i ordered a Coil Rail. I pray to God this will fix it becasue I am about to find a older XJ and buy and drive this on off a cliff.
ottexj2000
NAXJA Forum User
- Location
- Guilford, CT
My XJ still has a misfire. So last night I did a compression test on it and came up with the following results.
#1-160 psi
#2-135 psi
#3-100 psi
#4-160 psi
#5-175 psi
#6-155 psi
I know from this Cylinder #3 is the lowest outta the bunch. But what parts could be bad? I know it cant be good. I guess what I am asking is it really worth it to fix this or should i just keep driving and look for another XJ. Any help would be greatly appreciation. Thanks
#1-160 psi
#2-135 psi
#3-100 psi
#4-160 psi
#5-175 psi
#6-155 psi
I know from this Cylinder #3 is the lowest outta the bunch. But what parts could be bad? I know it cant be good. I guess what I am asking is it really worth it to fix this or should i just keep driving and look for another XJ. Any help would be greatly appreciation. Thanks
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Well, you could pull the #3 plug and shoot a little oil in the cylinder and then repeat the compression test. No improvement, its probably a valve.
However, it was recommended earlier that you use the Mopar Combustion Chamber cleaner. You could have some carbon buildup on the valve/valve seat of #3.
I'm not a great believer in "miracle in a can" solutions, but it would be a shame to pull the head on an engine, high mileage or not, with such good compression in 5 of 6 cylinders.
However, it was recommended earlier that you use the Mopar Combustion Chamber cleaner. You could have some carbon buildup on the valve/valve seat of #3.
I'm not a great believer in "miracle in a can" solutions, but it would be a shame to pull the head on an engine, high mileage or not, with such good compression in 5 of 6 cylinders.
ottexj2000
NAXJA Forum User
- Location
- Guilford, CT
Sorry I forgot to add that I did add some oil to #3 and there was no change. And I did try the Mopar Combustion Chamber Cleaner and there was a very cmall change in the way the XJ ran.
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Well, I would say valve/valve seat then.
You can do a leakdown test to confirm.
You can do a leakdown test to confirm.
jeepcj/jeepxj
NAXJA Forum User
- Location
- New Hampshire
How do you conduct a leakdown test?
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Quick and dirty you need an air hose fitting threaded to fit the spark plug hole in the head. Bring the cylinder you are testing to TDC compression stroke--valves closed--feed in air and listen with a vinyl tube in one ear for a STRONG sound of escaping air in the exhaust or intake.
You may have to jam a wedge of some kind in the accessory belt/pulleys to keep the engine from being forced away from TDC by the air pressure.
You can always detect a little sound from the valve cover and crankcase, that is normal.
More sophisticated buy a leak down tester, it will have the fittings and one or two gauges.
You may have to jam a wedge of some kind in the accessory belt/pulleys to keep the engine from being forced away from TDC by the air pressure.
You can always detect a little sound from the valve cover and crankcase, that is normal.
More sophisticated buy a leak down tester, it will have the fittings and one or two gauges.
LazersGoPEWPEW
NAXJA Forum User
- Location
- Los Angeles, CA
How do you get a computer update for that issue? Mine has a cylinder 3 misfire.
jneary
NAXJA Forum User
- Location
- springfield, virginia
the dealer has the ability to do that. the software info is provided from chrysler
winterbeater
NAXJA Forum User
- Location
- Royal Oak, Michigan
Any idea what that costs? It should be free, because they should have done it right in the first place.
jneary
NAXJA Forum User
- Location
- springfield, virginia
usually about an hour labor. its not free. you should get the problem properly diagnosed to confirm this is an applicable repair. you should work for free or discounted wages.
Talyn
NAXJA Forum User
- Location
- Radford, Communistwealth of Virginia
There isn't a PCM update for heat soak on 00-01s, the update is for a cold start issue. The TSB for the heat soak issue puts a heat shield over injector #3
winterbeater
NAXJA Forum User
- Location
- Royal Oak, Michigan
I just meant that Chrysler "should" treat that as an extended warranty item, not that the mechanic should work for free. They get paid for warranty work.
jneary
NAXJA Forum User
- Location
- springfield, virginia
if you purchased an extended warranty, depending on the level, it may be covered
Tall Shadow
NAXJA Forum User
- Location
- Metro Detroit, Michigan
Is the "Heat Soak issue" something that happens after a certain number of miles or years on the XJs?
I ask because I'm having a heat soak misfire on my 2000 XJ with 152K. It was fine until this last spring. I have replaced the plugs, coil rail, and I feel like I'm chasing gremlins!!:gonnablow
I keep getting misfire codes, and had not thought to check the injector side of the system....because it was acting like an ignition issue.
I can run it back & forth to work (30 miles almost all highway) and it runs great, but once the airflow drops for a short time (like in normal city driving) it will start to misfire until it is shut off, and cools down again. The temp never goes over 210, but it still starts to miss. It is driving me crazy! :wow:
Tall Shadow :flipoff:
