2000 Dodge Durango misfiring
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2000 Dodge Durango misfiring
I own a 2000 Dodge Durango 4 WD with a 5.9 L V8. I have the trouble codes telling me that cylinders 1, 2, and 4 are misfiring. I replaced the rotor button, distributor cap, plug wires, and spark plugs and it is still misfiring. If I start it more than once, it will eventually not start until I let it sit for a minute or two. It runs very rough until I rev it up. As soon as I let off the gas, it runs rough again. Any suggestions as to what to check next? I don't want to keep putting money into it and not fix the problem. I'm sure that's the first time anyone here's heard that.
Captain
Joined: Jan 2011
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From: Central Missouri
Have you checked to see if your plenum gasket is blown? It can cause a lot of issues, including fouling spark plugs, vacuum leak, and clogged CAT.
One thing you can try, since the plugs are relatively new...is to disconnect and UNSCREW the forward O2 sensor so there is literally a 'hole' in your exhaust pipe. Then start it and see if it runs any better. You'll get a code because the engine isn't reading from that forward O2 sensor, but if it runs any better overall that means your CAT is clogged.
To check the plenum gasket, disconnect and unbolt the throttle body and move it to the side. Peer down in with a flashlight and look at the steel pan straight down in the bottom of the intake. That's the plenum. It should be for the most part clean but if the plenum gasket is blown, you'll see oil pooling. If you do see oil pooling, the gasket is bad and must be fixed.
This is also a tad more complex than just changing the gasket and opinions will vary greatly at this point. Some just change the gasket. Some replace the steel pan with an after market aluminum one, and some will suggest while you have the intake off to replace the water pump and timing set.
Keep it simple though. Remove that forward O2 sensor, see if it runs better or not, and then check inside the intake for oil and report back. We'll take it step by step after that.
One thing you can try, since the plugs are relatively new...is to disconnect and UNSCREW the forward O2 sensor so there is literally a 'hole' in your exhaust pipe. Then start it and see if it runs any better. You'll get a code because the engine isn't reading from that forward O2 sensor, but if it runs any better overall that means your CAT is clogged.
To check the plenum gasket, disconnect and unbolt the throttle body and move it to the side. Peer down in with a flashlight and look at the steel pan straight down in the bottom of the intake. That's the plenum. It should be for the most part clean but if the plenum gasket is blown, you'll see oil pooling. If you do see oil pooling, the gasket is bad and must be fixed.
This is also a tad more complex than just changing the gasket and opinions will vary greatly at this point. Some just change the gasket. Some replace the steel pan with an after market aluminum one, and some will suggest while you have the intake off to replace the water pump and timing set.
Keep it simple though. Remove that forward O2 sensor, see if it runs better or not, and then check inside the intake for oil and report back. We'll take it step by step after that.
Thread Starter
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Registered User
Joined: May 2012
Posts: 8
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Have you checked to see if your plenum gasket is blown? It can cause a lot of issues, including fouling spark plugs, vacuum leak, and clogged CAT.
One thing you can try, since the plugs are relatively new...is to disconnect and UNSCREW the forward O2 sensor so there is literally a 'hole' in your exhaust pipe. Then start it and see if it runs any better. You'll get a code because the engine isn't reading from that forward O2 sensor, but if it runs any better overall that means your CAT is clogged.
To check the plenum gasket, disconnect and unbolt the throttle body and move it to the side. Peer down in with a flashlight and look at the steel pan straight down in the bottom of the intake. That's the plenum. It should be for the most part clean but if the plenum gasket is blown, you'll see oil pooling. If you do see oil pooling, the gasket is bad and must be fixed.
This is also a tad more complex than just changing the gasket and opinions will vary greatly at this point. Some just change the gasket. Some replace the steel pan with an after market aluminum one, and some will suggest while you have the intake off to replace the water pump and timing set.
Keep it simple though. Remove that forward O2 sensor, see if it runs better or not, and then check inside the intake for oil and report back. We'll take it step by step after that.
One thing you can try, since the plugs are relatively new...is to disconnect and UNSCREW the forward O2 sensor so there is literally a 'hole' in your exhaust pipe. Then start it and see if it runs any better. You'll get a code because the engine isn't reading from that forward O2 sensor, but if it runs any better overall that means your CAT is clogged.
To check the plenum gasket, disconnect and unbolt the throttle body and move it to the side. Peer down in with a flashlight and look at the steel pan straight down in the bottom of the intake. That's the plenum. It should be for the most part clean but if the plenum gasket is blown, you'll see oil pooling. If you do see oil pooling, the gasket is bad and must be fixed.
This is also a tad more complex than just changing the gasket and opinions will vary greatly at this point. Some just change the gasket. Some replace the steel pan with an after market aluminum one, and some will suggest while you have the intake off to replace the water pump and timing set.
Keep it simple though. Remove that forward O2 sensor, see if it runs better or not, and then check inside the intake for oil and report back. We'll take it step by step after that.
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Done
I disconnected and unscrewed the forward O2 sensor and it still ran horribly. I also removed the throttle body. The plenum looked a little dirty, but I didn't see any oil pooling that I could tell. I've attached some pictures, but they aren't great. I actually took the throttle body off and looked as well. The places you can't see in the pictures are cleaner. This vehicle is about to turn 200,000 miles. Thanks for the help so far. Let me know what else you think.
Last edited by jthayer5; Mar 24, 2013 at 09:22 PM.
To check the plenum for leakage, You need to do this. Remove the beather hose to the top of the throttle and plug, Then remove the PCV valve from the valve cover gromet. Then start the engine and put a finger over the gromet of the valve cover. Does your finger feel like its being suck into the valve cover? If it does, then the gasket is leaking and sucking in oil from the engine. I would also do three types of compression test too. 1st one a dry compression, 2nd running compression and last one wet compression test. And then post your findings.
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Fix one thing but not another
So I checked at the PCV valve to see if the plenum gasket was good, and it was okay. I did a compression test and found that I had no pressure on cylinder 2. I did a wet compression test and still nothing. So I took the valve cover off, and there it was - a broken valve spring. I replaced it and put it back together. It runs better but now it has a backfire. Does anyone know if the second valve from the front of cylinder two is the intake or exhaust valve? I'm guessing it is the exhaust valve since that is the one that had a broken spring, and I now have an exhaust backfire. Someone suggested I remove the valve cover and see if the rocker arms are moving when I crank it. Any other suggestions I should know about? It looks like I'm going to be digging deeper into this engine. Thanks for all the help so far.
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Fixed
It's been fixed for a while now but wanted to share to help anyone else if possible. It turned out that the broken valve spring was the problem. I had simply switched two plug wires when connecting them to the spark plugs. That was where the misfire that occurred after replacing the valve spring came from. Thanks for all the help. It got me headed in the right direction.
