2001 Dodge Ram How can low compession, valve problem through

Tiny
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  • 2001 DODGE RAM
Engine Performance problem
2001 Dodge Ram V8 Two Wheel Drive Automatic

01,1500,5.2 Code 308. Helping a friend, #8 plug is wet with fuel, injectors swapped, new wires etc. Still 308. Fine too 35 mph, missing and bogging to about 55 mph, 65mph fine untill have too back off. ( this is what he told me). I've read several post on missfires and how would a cylinder problem through a code if it is not a computer contolled problem? ie compression,valves. I am now envoveld with this since he still can not fix.


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Tuesday, November 18th, 2008 AT 9:33 PM

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Tiny
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Thought the pic was my avatar. Too tired to fix it
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Tuesday, November 18th, 2008 AT 9:51 PM
Tiny
JACOBANDNICKOLAS
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Hi:
Yes compression can cause the problem. Once it starts to get below 120 problems may begin. Have you checked the compression both dry and wet? What is the compression in that cylender? Also, I can't identify the code you listed. When you checked it, did you press and hold the odometer reset button while turning the ignition on?

Let me know.
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Tuesday, November 18th, 2008 AT 10:14 PM
Tiny
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Hello, I know compression or valves can cause this problem. My question was, how could this throw a code? I don't think low compression can throw a code. Did I really have to put PO infront of 308 for a Dodge code? I have not looked at the truck yet, just getting my eggs in a basket. I have my own scanner so I don't use the self diag to get codes. My thinking is compression can't fix it self ( or valves) to run fine at low speeds, bad at midrange and fine again at high speeds. There is something else going on to throw a code PO308, missfire #8 cyl. These are my questions.
Thanks
John
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Wednesday, November 19th, 2008 AT 7:04 PM
Tiny
JACK42
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Compression can throw a code. Doesnt have to be comp controlled to set misfire codes. Sorry the other mod should have assumed P0 at the front. Since you have a scanner, drive it and watch the injector waveform, this could be a bad injector, overfueling at part throttle. The PCM may have only thrown a code for cyl 8 too, pull other plugs to see if there is a problem with any others.
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Thursday, November 20th, 2008 AT 1:07 PM
Tiny
RASMATAZ
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A misfire in a specific cylinder should lead you to check the spark plug, fuel injector and compression.

Misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel
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Thursday, November 20th, 2008 AT 1:16 PM
Tiny
JNOVACK
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To diagnose a P0308 trouble code we begin by checking for proper fuel and ignition system operation, and then follow up with the less likely causes listed above, such as EGR and EVAP system problems. New style coil on plug applications have a high failure rate, and can be concluded faulty by swapping to another cylinder and checking to see if the misfire moves to that cylinder. This is a quick check
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Thursday, November 20th, 2008 AT 5:07 PM
Tiny
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Thanks for all your replies. I am a Marine Tech of 31 yrs. Lets start over, my 1st post says, injectors swapped, new plugs, new wires etc. #8 plug is wet, not lean. Has spark. Again, how will low compression thow a code? (Exactly how?) None of the engines I work on will throw a code for that.
I brought my compression kit home and my cyl leak down kit home. I will see the truck Sunday and get back.
Thanks
John
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Friday, November 21st, 2008 AT 10:42 PM
Tiny
RACEFAN966
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Ok this is back the others as it is possible to get a code that is not sensor related here is how it works. The computer monitors the engine while runnig after running a crankshaft postion learn procedure. A missfire code will be stored when more then a 2% missfire rate is measured during 2 trips (one on Cal models), or a 10 to 30% rate with one trip. Some of the possible caused are as follows cam or crank sensor, bad timing, ignition system fault, mechanical problems, fuel contamination or fuel pressure. This is what the computer is set to read so with that if it has low compression that is allowing it to see either a 2% or 10 to 30% missfire rate it will pic it up and send a code for the cylinder that is causing the problem. I hope this is more of the answer that you are looking for I can't explain it any better.
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Monday, November 24th, 2008 AT 12:33 PM

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