Grand am 2005 rough idle

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Teaboy

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I have a 2005 Grand Am with the 3.4 v6 recently the idle has become slower it has 160,000 miles on it at a light or stop sign you feel the engine might die
i changed the egr valve for an old one it made no difference
i cleaned the idle control valve and the maf sensor this made it run worse my scan tool says p300 misfire
could it just be the spark plugs need changing ?i last changed them at 100,000 miles Bosch platinum i think
at hwy speed its just fine only on idle there seems to be a problem you hear popping in the exhaust pipe
i checked the evap purge valve unplugged it took vaccum hose of was no vaccum until car warmed up
 
Plugs and plug wires if not recently changed. Also ignition coils if original are possible.
 
melsg5 said:
Plugs and plug wires if not recently changed. Also ignition coils if original are possible.
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I just drove around the neighbourhood runs great for 5 minutes then starts loping i thought coils were solid state
like a transistor = they either work or dont i guess maybe i will try plugs but a map sensor ,evap purge valve and idle control valve i am
willing to change all if need be, the problem became more apparent on Sunday after Christmas Dec 28th it was a hot day too .
 
Heat changes how things work including coils. Did you look at the list of possibilities for a P300 code?
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The mechanic at work feels the plug wires are bad he suggested that i run the car in the dark and look for arcing
I did tonight but did not see any he also talked about bad coils i will start by changing plugs and wires and go from there.
he feels like the sensors map ,idle control valve ,evap purge valve are not the problem he did suggest wiping down around
the butterfly/ throttle body with gum out i did but didnt have enough i did clear the codes .
 
Changed the plugs yesterday also put a new pcv valve and hose so should be a more sealed up vacuum .will drive to test shortly .
 
Teaboy said:
Changed the plugs yesterday also put a new pcv valve and hose so should be a more sealed up vacuum .will drive to test shortly .
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Did you test the plug wires with an ohmmeter? Standard is no more than 1k ohms per foot of wire.
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melsg5 said:
Did you test the plug wires with an ohmmeter? Standard is no more than 1k ohms per foot of wire.
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Sad to report car still has a miss ! , new plug wires coming this week on Amazon i buy from them cheaper prices compared to auto parts .
 
Teaboy said:
Sad to report car still has a miss ! , new plug wires coming this week on Amazon i buy from them cheaper prices compared to auto parts .
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Quite often you get what you pay for. Test them with an ohmmeter before wasting your time installing them.
 
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