Misfires, blinking check engine light after coolant flush
01-07-2017, 02:52 PM
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Misfires, blinking check engine light after coolant flush
2000 XJ - 168,000 mi - replaced the headgasket, intake manifold gasket, valve cover gasket, spark plugs, and thermostat two months ago and it's been running better than ever since. However, I checked the coolant the other day to make sure I was topped off and it looked a little brown. Before I did the head gasket, there was sludge in the radiator neck, which wasn't there now, but the coolant had a brown tint to it. So I decided to flush the coolant system completely. I flushed it 4 times with distilled water and finally it started running completely clear. Filled it up with 1.5 gal of coolant and poured distilled water in the rest of the way and let her run for a bit. Everything was great, the heat was hotter than ever and then out of no where check engine light came on. It felt and sounded fine, so I took it for a test drive and then the light started to blink and she started running rough and lost power. Got home, plugged the computer in and got 6 codes: P0123, P0300, P0301, P0304, P0306, and P0122.
So TPS and misfires... I cleaned the TPS a few months back because of a slightly rough idle and it seemed to work, but now I'm thinking it took a ****. As for the misfires what's the best way to proceed? Bad fuel rail? Bad coil pack? Although the coil pack is relatively new--replaced a year and half ago. Any help is greatly appreciated!
So TPS and misfires... I cleaned the TPS a few months back because of a slightly rough idle and it seemed to work, but now I'm thinking it took a ****. As for the misfires what's the best way to proceed? Bad fuel rail? Bad coil pack? Although the coil pack is relatively new--replaced a year and half ago. Any help is greatly appreciated!
01-07-2017, 05:56 PM
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Year: 1999
Model: Cherokee
Engine: 4.0
Don't throw parts at this. The codes should lead the way.
Start with the lowest numbered codes and you have two of them for the throttle position sensor. It can't be cleaned; should be replaced and I would highly recommend that you buy a MOPAR TPS directly from a Jeep dealer.
After replacing it, clear the codes and drive it and see if any further codes return. Know that a flashing check engine light indicates a serious misfire, which if not resolved quickly, will trash your catalytic converter for starters. I'd recommend parking it until this is fixed or you'll have bigger fish to fry.
Start with the lowest numbered codes and you have two of them for the throttle position sensor. It can't be cleaned; should be replaced and I would highly recommend that you buy a MOPAR TPS directly from a Jeep dealer.
After replacing it, clear the codes and drive it and see if any further codes return. Know that a flashing check engine light indicates a serious misfire, which if not resolved quickly, will trash your catalytic converter for starters. I'd recommend parking it until this is fixed or you'll have bigger fish to fry.
Last edited by tjwalker; 01-07-2017 at 06:00 PM.
01-07-2017, 07:05 PM
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Don't throw parts at this. The codes should lead the way.
Start with the lowest numbered codes and you have two of them for the throttle position sensor. It can't be cleaned; should be replaced and I would highly recommend that you buy a MOPAR TPS directly from a Jeep dealer.
After replacing it, clear the codes and drive it and see if any further codes return. Know that a flashing check engine light indicates a serious misfire, which if not resolved quickly, will trash your catalytic converter for starters. I'd recommend parking it until this is fixed or you'll have bigger fish to fry.
Start with the lowest numbered codes and you have two of them for the throttle position sensor. It can't be cleaned; should be replaced and I would highly recommend that you buy a MOPAR TPS directly from a Jeep dealer.
After replacing it, clear the codes and drive it and see if any further codes return. Know that a flashing check engine light indicates a serious misfire, which if not resolved quickly, will trash your catalytic converter for starters. I'd recommend parking it until this is fixed or you'll have bigger fish to fry.
Edit: deleted a stupid question.
Last edited by runt; 01-07-2017 at 07:18 PM.
01-08-2017, 03:58 AM
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Year: 2000
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Thinking this does not really apply but going to throw it out there. I replaced the coolant in my '00. Usual procedure for me is to fill it up best I can, run till it starts wanting to come out of the radiator, cap it off, run the Jeep, let it cool, check and top off accordingly. Then spend the next few days driving her, letting her cool, checking, and top off accordingly till I get to the levels I want. So on the first day of driving the Jeep after I did the initial procedure I got a CEL. Never checked what the code was. My little theory is that an air pocket hit the coolant temp sensor. The one in the thermostat housing. The Jeep had a little hissy fit and threw the CEL. Filled up more after she cooled, cleared the CEL, and all was fine. The reason I think this is because I know first hand how that coolant temp sensor can mess with how a '96 Jeep I used to own runs. Thought it just needed a tune up when running like crap but turned out to be the sensor.
01-21-2017, 09:04 AM
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Don't throw parts at this. The codes should lead the way.
Start with the lowest numbered codes and you have two of them for the throttle position sensor. It can't be cleaned; should be replaced and I would highly recommend that you buy a MOPAR TPS directly from a Jeep dealer.
After replacing it, clear the codes and drive it and see if any further codes return. Know that a flashing check engine light indicates a serious misfire, which if not resolved quickly, will trash your catalytic converter for starters. I'd recommend parking it until this is fixed or you'll have bigger fish to fry.
Start with the lowest numbered codes and you have two of them for the throttle position sensor. It can't be cleaned; should be replaced and I would highly recommend that you buy a MOPAR TPS directly from a Jeep dealer.
After replacing it, clear the codes and drive it and see if any further codes return. Know that a flashing check engine light indicates a serious misfire, which if not resolved quickly, will trash your catalytic converter for starters. I'd recommend parking it until this is fixed or you'll have bigger fish to fry.
Last edited by runt; 01-21-2017 at 09:23 AM.
01-21-2017, 12:17 PM
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Ok, so I've been working on my truck but not getting much resolved. First, I bought MOPAR sensors and installed them, cleared the codes and drove it for half a day. Truck was running fine without any CEL but them it came on, first solid, then blinking. Immediately went home, pulled codes and got a cylinder 6 misfire. No more sensor codes or any other misfires. So my next step was swapping injector 6 with injector 1, to try and see if the 6 injector is bad. Did that, cleared the codes, and she ran fine for half a day again before misfiring and CEL coming on. Pulled codes, and this times its both cylinders 1 and 6 misfiring and a P0300 code. Next, I removed the coil pack and tested it... and it's fine. All readings are right where they should be according to the service manual. Tested the connector too, and thats fine. What should be next? Fuel rail?
1. You mentioned you replaced MOPAR sensors (plural). Did you replace more than the TPS?
2. Onto the misfires. Before doing anything else, you should verify fuel pressure. Must be done with a gauge which can be rented inexpensively from many parts stores, call around for availability. The fuel pressure spec. for the 2000 is 49 psi, plus or minus 5 psi.
3. What brand of spark plugs are you running and what did you gap them at? The 00-01 4.0 engine can be a bit finicky about plug brand.
4. Never hurts to get a compression test as a general snapshot of how things are internally. The compression spec. for the 4.0 is 120-150 with no more than a 30 psi variation between cylinders.
5. Are these original fuel injectors? They might be getting long in the tooth. Start with a simple resistance check of all of them.
6. Questions for you. Why did you replace the head gasket? Was the engine ever overheated? Did you have the head gone through and checked for cracks by a machine shop before you reinstalled it?
Last edited by tjwalker; 01-21-2017 at 12:37 PM.
01-21-2017, 03:35 PM
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Actually, you are making significant progress. Namely, the throttle position sensor issues seem to be gone. Good start!
1. You mentioned you replaced MOPAR sensors (plural). Did you replace more than the TPS?
2. Onto the misfires. Before doing anything else, you should verify fuel pressure. Must be done with a gauge which can be rented inexpensively from many parts stores, call around for availability. The fuel pressure spec. for the 2000 is 49 psi, plus or minus 5 psi.
3. What brand of spark plugs are you running and what did you gap them at? The 00-01 4.0 engine can be a bit finicky about plug brand.
4. Never hurts to get a compression test as a general snapshot of how things are internally. The compression spec. for the 4.0 is 120-150 with no more than a 30 psi variation between cylinders.
5. Are these original fuel injectors? They might be getting long in the tooth. Start with a simple resistance check of all of them.
6. Questions for you. Why did you replace the head gasket? Was the engine ever overheated? Did you have the head gone through and checked for cracks by a machine shop before you reinstalled it?
1. You mentioned you replaced MOPAR sensors (plural). Did you replace more than the TPS?
2. Onto the misfires. Before doing anything else, you should verify fuel pressure. Must be done with a gauge which can be rented inexpensively from many parts stores, call around for availability. The fuel pressure spec. for the 2000 is 49 psi, plus or minus 5 psi.
3. What brand of spark plugs are you running and what did you gap them at? The 00-01 4.0 engine can be a bit finicky about plug brand.
4. Never hurts to get a compression test as a general snapshot of how things are internally. The compression spec. for the 4.0 is 120-150 with no more than a 30 psi variation between cylinders.
5. Are these original fuel injectors? They might be getting long in the tooth. Start with a simple resistance check of all of them.
6. Questions for you. Why did you replace the head gasket? Was the engine ever overheated? Did you have the head gone through and checked for cracks by a machine shop before you reinstalled it?
I replaced the head gasket because I noticed worsening brown sludge in the radiator. Not just brown fluid, but a thick chocolatey looking sludge. I asked around and searched the google and saw that I probably needed a head gasket. The old head gasket was indeed damaged.
Yes, the engine started to overheat once, about 4 years ago, but not for long and with no symptoms afterward. And no, I did not take the head to a machine shop, but it was inspected as thoroughly as I could during the cleaning process and I didn't see any signs of cracks at all.
A new issue! I was checking for vacuum leaks and noticed a small crack in the intake manifold, right near the first injector and the flange where the bolt grabs it. I sprayed some starting fluid on the crack but didn't get a noticeable surge. I swear I can hear a slight sucking around the intake manifold, but I cannot identify exactly where it's coming from and my friend tells me I'm hearing things. What's puzzling me about this now is that if it's a leak from the intake manifold, wouldn't the truck be misfiring as soon as the engine was running? As I said, I seem to only be getting the CEL and the misses after driving for a bit. Idling and for some miles, she's running fine...
Thanks for your help with this!
Last edited by runt; 01-21-2017 at 03:38 PM.
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01-28-2017, 12:26 PM
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Actually, you are making significant progress. Namely, the throttle position sensor issues seem to be gone. Good start!
1. You mentioned you replaced MOPAR sensors (plural). Did you replace more than the TPS?
2. Onto the misfires. Before doing anything else, you should verify fuel pressure. Must be done with a gauge which can be rented inexpensively from many parts stores, call around for availability. The fuel pressure spec. for the 2000 is 49 psi, plus or minus 5 psi.
3. What brand of spark plugs are you running and what did you gap them at? The 00-01 4.0 engine can be a bit finicky about plug brand.
4. Never hurts to get a compression test as a general snapshot of how things are internally. The compression spec. for the 4.0 is 120-150 with no more than a 30 psi variation between cylinders.
5. Are these original fuel injectors? They might be getting long in the tooth. Start with a simple resistance check of all of them.
6. Questions for you. Why did you replace the head gasket? Was the engine ever overheated? Did you have the head gone through and checked for cracks by a machine shop before you reinstalled it?
1. You mentioned you replaced MOPAR sensors (plural). Did you replace more than the TPS?
2. Onto the misfires. Before doing anything else, you should verify fuel pressure. Must be done with a gauge which can be rented inexpensively from many parts stores, call around for availability. The fuel pressure spec. for the 2000 is 49 psi, plus or minus 5 psi.
3. What brand of spark plugs are you running and what did you gap them at? The 00-01 4.0 engine can be a bit finicky about plug brand.
4. Never hurts to get a compression test as a general snapshot of how things are internally. The compression spec. for the 4.0 is 120-150 with no more than a 30 psi variation between cylinders.
5. Are these original fuel injectors? They might be getting long in the tooth. Start with a simple resistance check of all of them.
6. Questions for you. Why did you replace the head gasket? Was the engine ever overheated? Did you have the head gone through and checked for cracks by a machine shop before you reinstalled it?