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Hope somebody can help. My 2005 Ram 1500 Hemi had a check engine light on. 68K miles so I put in iridium plugs and new wires. Then the engine light started flashing and truck ran poorly, tach jumping around. Then I read here that I should have used stock plugs. So I replaced the plugs with standard Champions. But I still occasionally have a flashing engine light and poor running. This seems to only happen when the truck is cold and once warmed up, the problem goes away. Does anybody have an idea what could be wrong. I've also read here that maybe I should unhook the battery and reset the computer. Thanks for any help.
 

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Start with the '******* reset' as you stated. I doubt if this is a fix but who I could be wrong

This is the best 20 dollar bill Iv spent for the RAM.......
http://www.amazon.com/Autel-MaxiSca..._1?s=automotive&ie=UTF8&qid=1333304482&sr=1-1

It reads and will delete, if you want it to, any trouble codes. Take the code it gives you and put it in Google, BAM you know whats wrong. Clearing a Tcode is not a fix, the truck computer will find the issue again unless you did the fix.

As for what may be wrong with yours, I dont know. Sounds like a fuel feed or air issue. Maybe EGR? That a $40, 4 bolt fix
 

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Obviously you need to take it to an autozone or whatever parts store you have near by and get the stored code pulled. That will help determine the problem for sure. Cold start and rough running with the troubles your describing actually sound like a bad battery. Pull the codes and you will have a much better idea.
 

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A flashing check engine light is bad. You shouldn't drive the vehicle. You need to get the codes and post them here and we can help you.

P0420 means catalytic efficiency below threshold. Either one of the downstream O2 sensors is faulty, the connection or wiring is faulty, or the catalytic converter is faulty.
 

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Ya the code i got was 0420. The guy i got off said that its because he put regular gas in it. He says i needed to run with 89 octane becasue of the emisson is that why its on?
No that's not correct.

How many miles are on the truck? Any running issues at all? If it's running poorly it's probably a clogged/faulty catalytic converter. If it runs fine it's probably a bad sensor.
 

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What's a km????? :)

That's roughly 100,000 miles and that's a fair amount of mileage. It is possible the sensor is faulty. Also possible the cat is clogged.

If it's running fine I'd try the sensor. Although you don't really need to replace them if it is running ok and the light doesn't bother you too much. It's just an emissions thing, it doesn't effect the truck in any other way. Now, if the truck starts running poorly it could be a clogged cat.

I'd guess a new downstream sensor is ~$50 to $100.
 

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^it depends. If it's an upstream O2 sensor then yes it will effect mpg. But your code is a downstream O2 sensor, which has no effect on anything except monitoring emissions.
 

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Changing the muffler or adding a cutout will not effect the engine light.

An 05 hemi ram should get somewhere around 15mpg avg.

P0420 signifies a downstream(post cat) sensor. It could be either side if there are two(probably is two). It's either the sensor(s), the cat(s), or a wiring/harness issue.

There are other possibilities but unlikely. An exhaust leak, coolant leak(into the engine), etc can cause this. But if you don't have any running issues they are highly unlikely.
 

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that'd be my guess. Best place to start is to inspect the harness to look for frayed wires or loose connections. Disconnect and reconnect the downstream sensors and see if that helps. You can also clear the code and see if it comes back.
 
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