Misfire

[richyr]

I got a Chevy 2007 Tahoe few days ago and first it showed multiple misfires. I cleared the DTC codes and now it's showing the 4th cylinder misfire. Motor even outs at higher rpm but runs rough and shakes at idle.any idea or common problem known to be with this year. Was told a crankshaft sensor could cause it but my experience says do a complete tune up . wires plugs and possibly coil packets.Any ideas or past experience?

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[Doubeleive]

swap the coil packs and see if the misfire follows the coil, that's going to be the easiest place to start

 

[Kraig]

If you just got it and don’t know the maintenance history, change plugs and wires while you’re swapping a coil.

 

[richyr]

I tested the plug wires with my timing light and all the wires are showing that they are firing but going to look at plugs today. Someone said something about a crankshaft sensor causeing the problem but don't think it could be

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[avalonandl]

Well without reading the codes your flying blind.

 

[richyr]

I've been reading codes whole time lol keeps throwing p0304. Switched out coil packs and still throwing same code on misfire on cylinder 4 .checked spark plug looked almost new and smelled like gas.still doing same thing.first it was multiple fire but now it's only throwing that code

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[Doubeleive]

I've been reading codes whole time lol keeps throwing p0304. Switched out coil packs and still throwing same code on misfire on cylinder 4 .checked spark plug looked almost new and smelled like gas.still doing same thing.first it was multiple fire but now it's only throwing that code

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if you are SURE that the coil packs, plugs & wires are good, then check for a intake vacuum leak -spray some starting fluid around the edges of the intake gasket and listen for a change in idle

 

[kbuskill]

Cylinder 4 is an AFM cylinder. Not good news.

 

[RET423]

I am betting you need a cam and lifter replacement.

 

[Kraig]

Swap the #4 injector with another—if it’s sparking and smelling like fuel something is definitely amiss. If it’s not that i’d Start looking at AFM issues.