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Discussion Starter #1
For the past month I have had an issue that has been perplexing me and my mechanic. I'll start up the truck, and after about 200 ft I come to a stop. The truck will dip below 500 rpm, and shake violently. It does it for 30 seconds tops. After that the truck will continue on as normal. The CEL came on, and was spitting the obligatory P0300 code. I took it down to my mechanic who did some work on it. I did some work on it too. This is what has been done so far:

All O2 sensors replaced
IAC valve cleaned
TB cleaned
Seafoam treatment

Even with all of this work done, it continues to do the same thing. I feel as though it may be idling a little heavy, but nothing like when I start it in the morning. I've heard that this problem could be a range of issues, from asymmetrical valve, to ignition coil. I thought I'd get y'alls take. Thanks in advance.
 

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You need to find out which cylinders are misfiring. Still sounds like heavy carbon buildup on the valves to me.
 

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Discussion Starter #3
Wouldn't something like a Seafoam treatment rid most carbon build-up? I've run two for good measure, and there has been no change. The mechanic ran a full diagnostic test, and he cant seem to pinpoint which cylinder is misfiring.
 

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A DRB III scan tool will tell you which cylinder is misfiring. If the carbon buildup is thick enough, SeaFoam won't fix it. The heads will have to come off and the carbon removed with a wire wheel on a grinder or the valves will need replacing.
 

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Discussion Starter #5
Thanks RamTech. Is there a possibility of it being a vacuum leak? I've heard that these are common issues also.
 

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If you want to check for a leak yourself, get a can or carb cleaner and spray any suspect areas while the engine is running. If there's a leak, you'll hear a change in engine rpm.
 

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Discussion Starter #9
So I brought the truck to multiple mechanics since my problem began. I had one do as you had said. Apparently it wasn't the problem. So this is the list of things that have been replaced/fixed/done:

Camshaft sensor replaced
crankshaft sensor replaced
All O2 sensors replaced
All Spark plugs replaced
Decarb - twice
IAC valve checked
Fuel treatment

My last trip was made to the dealer service dept, who claimed it was faulty spark plugs. It wasn't. So it's been 5 months now. Not even a Dodge mechanic could diagnose and fix it. What the hell could it be?

I read this somewhere:
Vehicle Issue Engine Runs Rough. MIL On. Will have one or more of Fault Codes
P0300 - P0308.;1999 - 2005 3.7, 4.7, 5.7 engines. Possible fault codes P0300,
P0301, P0302, P0303, P0304, P0305, P0306, P0307 and P0308. Cylinder leakage
test indicates air leakage past valve. There is no visible problem with valve
when head is removed.





Recommendation With the cylinder head removed, use a known good valve and coat
the valve facing / valve seat contact area with valve lapping compound. By
hand, firmly pull the valve against the seat and rotate valve a few times.
Remove the valve and check for a Symmetrical contact pattern on valve seat. If
the pattern is not symmetrical replace cylinder head. If pattern is good,
replace suspect valve.

I have just about given up on this truck.
 

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Is it just the P0300 or are you getting specific cylinder misfire codes too?
How is the wiring harness? No frays or cut wires?
Stock Cam?
If the wiring harness is okay then i would have the valve covers pulled to check the push rods to make sure they are seated correctly.
 

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Discussion Starter #11
It looks as though the problem not only persists, but it got worse. There are no frayed wires. It is the stock cam. I'm only getting p0300.

I took the truck to dodge who couldn't diagnose it. They believe it's my universal muffler I replaced because the previous owner had put a flowmaster 40 on it. They claim that the baffle may be loose. I really don't thinks it's that though because there are fumes coming out of the pipe.

Yesterday I was driving at about 35mph and went to speed up. My Rpms wouldn't go about 3k, the needle twitched between 2k and 3k, and my truck remained at 35mph. I took my foot off the gas and then slowly pressed it again, and the problem stopped. About half an hour later I came to a stop, and when I went to accelerate my truck got up to about 10mph and the engine shut down. The car didn't lose all power, and I was able to crank it over again. Today I had the same experience when the truck died and I cranked it right back up.

This is just getting ridiculous.
 

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Discussion Starter #12
So after 7 months, and over $3k in work, my truck is fixed. It turns out it was one of the computers. They way I look at it, I will have very little to worry about for a long while. Thanks for all your input. It's been a rough past couple of months, but I'm glad my trucks is finally back to normal. :smileup:
 

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Discussion Starter #13
So, I thought my problem disappeared, but I was wrong. I'm going on 9 months now with the exact same problem. I'll crank up the truck. I will drive 100 yards to my first stop. The the truck shakes. Then when I step on the accelerator, my truck literally roles. I will take my foot off of the accelerator, reapply (this is usually where the CEL will flash, and then stay on with the p0300 code) and the truck will drive as though nothing happened. I've had the truck scoped, and no one can tell me which specific cylinders are misfiring. Has ANYONE seen or heard of anything like this. I've dumped way too much money into it to get rid of it.

things done on vehicle:
- new PCM
- new coil pack
- replaced all 02 sensors
- replaced camshaft and crankshaft sensors
- new muffler and cats
- new spark plugs
- throttle body cleaned
- new Throttle Position Sensor
- new Engine Coolant Temperature sensor
- new IAC valve
- new cats and muffler
- new fuel pump assembly
- BG Fuel Treatment
- Injectors check out
- Compression fine
- no vacuum leaks
- wiring looks to be ok. No frays or corrosion damage
- seafoam treatment
 

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Discussion Starter #15
I thought that my #6 coil was shot. When I removed it, I found that they were the coils from when the truck was purchased. I went ahead and replaced them all because the truck has 67k on it. It's not the pack, however.

The problem only occurs at start. There is no audible miss while I'm driving. Only when I start up the truck. There is also some hesitation (I've heard it called fish biting, which most accurately describes what I feel). I have replaced nearly all of my sensors. I am going to attempt to replace my map sensor today.

I am not witnessing any black or nasty smelling smoke coming from the exhaust.

If you know anyone that may know what this could be, please let them know. I am at my wit's end with this truck.
 

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Discussion Starter #17
I'm baaaaaaaaaack. It's doing it again :4-angermax: . It seems to only act up when it warms up outside. Anyone have any other solutions to this problem?
 

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What you said about the temperature led me to think lean misfire and that lead me to this http://www.random-misfire.com/. Maybe there is something in there that you haven't had checked, or google lean misfire for more causes. I hope you can get this sorted, I would have blown up my truck if it gave me this much trouble.
 
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