2001 dodge ram 1500 slight Misfire Shudder/Stumble at idle in park or stop light/stop sign Please Help!!!

[nxm10]

I just bought a 2001 dodge ram 1500 5.9 with 170,000 miles and it had a slight misfire shudder/stumble at idle so i replaced the plugs and wires but the problem didn't go away. I driving around town today and i got a p308 trouble code (misfire detected on cylinder #8) no other codes present. The misfire is only at idle theres no other problems at all while driving. Other then the slight misfire shudder/stumble at idle in park or a stop light or stop sign the truck runs great. Would a bad intake plenum gasket cause this? Any ideas/advice would be appreaciated.

Thanks

UPDATE: I checked compression on three cylinders and on #8 which is where the computer detected the misfire theres only between 55 and 60 pounds and on cylinder #'s 2 and 4 there was 125 pounds so im thinking a bad or improperly seated or stuck intake or exhaust valve on #8 causing the compression loss. I also looked down the intake with a flashlight and its clean and dry as can be.

And just an fyi i just bought the truck about three days ago and it sat for at least 9 months to a year before i got it.

[Chris Stewart]

I check for cracked vacuum hoses, loose intake manifold and throttle body bolts when I get that....easy stuff first.

[jamesslcx]

nxm 10 check for vacuum leaks first. What kind of plugs were and are in your engine? How new is the distributor cap? Yes check the basics first. Sometimes the dodge engines don't like precious metal plugs.

[nxm10]

Originally Posted by Chris Stewart

I check for cracked vacuum hoses, loose intake manifold and throttle body bolts when I get that....easy stuff first.

Checked and all vacuun hoses good, intake and tb is nice and tight.

[nxm10]

Originally Posted by jamesslcx

nxm 10 check for vacuum leaks first. What kind of plugs were and are in your engine? How new is the distributor cap? Yes check the basics first. Sometimes the dodge engines don't like precious metal plugs.

I installed autolite copper core plugs the dealer said thats what came stock in the truck. Not sure about the distributor cap but i checked the spark with a spark plug tester and it has good spark is good at the plug.

[Chris Stewart]

Originally Posted by nxm10

And just an fyi i just bought the truck about three days ago and it sat for at least 9 months to a year before i got it.

Sounds like a little rust on #8 valves & seats.
I'd take an hour, speed limit drive on a freeway/interstate somewhere and see if that cleans them up.
Maybe some 89 octane for the extra detergents.

[jamesslcx]

nxm, yes possibly a sticking valve, try running some fuel system cleaner through it when you can.

[jamesslcx]

I did not see your edit, hopefully not a burnt valve or worse, try the fuel system cleaner and run it kind of hard and see if that helps. Also run a detergent in the oil and change it if you haven't already.