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I am still working on the 02 Dodge Caravan 3.3 flex fuel. The van finally got another code P0420. Checked out code it says cat efficiency code. I know that it means I need a cat. But I am confused as to why it is popping through manifold. Changed coil packs, changed spark plugs. Checked fuel pressure. Fuel pressure is good. My last experience with a bad cat the car had no power what so ever and ran bad. The van runs good. So I changed down stream O2 sensor. My check engine light went out. Didn’t understand that one. But now back on and still showing cat code. Can the cat cause a popping sound through manifold? Hadn’t ran across that so I thought I would ask before I go and buy a cat. Don’t want to just throw money at it to see if it fixes it. The van has 209,000 on it. I have had a couple of other people say it’s not the cat. But can’t give me any other ideas of things to check. Thanks in advance for any help.
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So the van runs good??? No codes other that P0420??? If CAT efficiency is the only problem and not restricted you may not have other codes. What do yo mean by “Popping”? Exhaust leak???
No not an exhaust leak. I will try to make a video of the noise for everyone to gear. The problem I will have with making the video is it only makes this noise while in gear and driving. No noises at idle. Will post video later tonight after I get off work. Maybe the sound it’s making might help figure out what problem is.
Yes. And over the last couple of weeks it starting to get worse. Being a flex fuel car I put E85 in it to see if it would help. A few months back the E 85 did help but now it is not. I would think that if the cat was plugged up it would be glowing under car. I don’t see that as of yet. With the E85 I have to let van warm up a bit or it chugs along until it warms up. Then after operating temp it starts the noise. I will make a video of it tonight with some help because it only does this when you have the van in gear and driving. Worse case I will have to brake torque it so the noise will happen for video
I suspect that it might be unburned fuel from a cylinder being released into the hot exhaust manifold and then igniting making a popping sound. Could be bad spark plug, spark plug wire, or injector issue.
I have been working on this can for a few days now. However I cannot get a video of the noise because you gave to be driving down the road. I tried to make a video but you can’t hear the noise. I have taken injectors out and had them checked out. They claim they are ok. I happen to notice that the top of the spark plugs where the wire connects at are showing signs of getting hot. They have a blue tint to them. I was checking foil and also noticed that one post showed a sign of being what call burnt. When I put the van back together it ran good but when I took on test drive started that noise again. This noise does not do it when I tried to brake torque it. So that idea didn’t work for me to get the video of the noise. When I hit the plugs from parts store I got platinum plugs. They said it was an upgrade from what I had. 3 of the old plugs had no electrode on the bottom of the plug. Could it be the coil causing the blue tint on the tops of the plugs or not hot enough of plugs for the van? I have to put some miles on it to see if cat code is still present. The noise I believe is actually coming from closer to the cat than the manifold but unsure because it will only do it when driving down the road under a load and accelerating like to go up a hill or to pass another car. Any ideas of how I can get a video of the noise would be appreciated. I know none of you are here to hear it and is hard to say what to do.
I suspect the excessive heat on your plugs will be caused by an exhaust restriction. Here is a video by Eric.
Ok worked on the dodge caravan again. Replaced cat. Found out that there was another issue that computer did not show. Had a misfire on more than one cylinder. Replaced plug wires. No change. Decided to change the coil. Then it ran good again. The exception was only when at operating temp. When it was cold it would misfire but computer kicked it up and gave me cylinder 4 misfiring. Checked plugs they all look the same. Switched plugs in cylinders 2,4. Runs like a champ again even cold. Took out on a test drive today and cat efficiency code back. Couldn’t have burned up cat didn’t run that long. It’s new. Kinda lost. Van doesn’t seem like it’s missing runs like it used to. It will even spin tires like it used to. No popping sound like I had before. So now I’m a list as to what to check. Any ideas?
Do you have a way to look at fuel trim data? Others on this site will dispute but I have seen fouled plugs (misfires) cause the P0420 and after driving clean for a while the code goes away. Fuel trim data would tell you if the O2 sensors and Cat are playing nice together.
Have you tested the wiring to the lower O2 sensor? What kind of replacement did you use, OEM or aftermarket?
My code reader does not allow me to look at fuel trim. I replaced the down stream o2 sensor with a aftermarket one. While trying to figure out what’s going on I got an error code showing misfire cylinder 4. The plugs are like 4 months old. I put new wires , new coil,new cat. Switched plugs around. I put cylinder2 in cylinder 4 and vise versa. Misfire went to cylinder 2. Changed all plugs again. So far no codes. Will keep updating.
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