5.3 Idle Misfire No Check Engine Light.

[2007VictoryRed]

I have a 2007 Silverado classic With a 5.3. From Day one The Truck seems to have a misfire but Not bad but noticable. The past month has been really Bad. But theres no check engine light at all. It can be felt at a stop light idleing, some times the RPM needle will boune around a bit, and you can fell it if you were to lean on the truck. I have plugged it into my cheap obd2 scan tool theres no codes that come up. I have taken it to 2 different dealers, they have also Plugged it In to there scan tool, They say theres nothing we can do if there no codes. This past week i have put back the stock air filter, and exhaust, that made no differece. The only thing that i can think of are the spark plugs, plug Wires, coil, Or injectors. The truck is never driven hard or pulled anything, I use Chevron Or shell 89 gas, all different gas stations, I never let the gas tank go lower then 1/4 tank. What else can I do? Is there anything i can do?

 

I was looking into use seafoam, And 3m Fuel injector cleaner. And doing a basic tune up. Changing plugs and wires also testing the coils.

 

Thanks for any help.

[Alljackedup408]

at the dealer did they check for updates to your PCM?

[2007VictoryRed]

at the dealer did they check for updates to your PCM?

They never said anything About the PCM But they did update something to do with e85. The paper work says.

 

SERVICE UPDATE-INVENT/CUST VEHS E85 VFFS UPDATE REPGM ECM *EXPIRES 8YR/80K MI

 

Y0124 - 06162 PRODUCT ENHANCEMENT - ENGINE CONTROL MODULE REPROGR

 

Is there more updates?

[Alljackedup408]

im not sure... gm is always sending updates out.. wouldnt hurt to ask them.

[KENNHON]

If you have 60k miles[in less than 3 yrs]...u might try checking for vacuum leak[i doubt that wires are bad[unless u man-handled pulling wires from plugs].

Definitely check the vacuum line from cannister to intake /EVP valve. That was my problem--- if it doesn't misfire when accelerating.. probably vacuum leak. several ways of checking for vac.leak. It doesn't throw codes if the MAP sensor doesn't detect big leak

[2COR517]

Try a new set of AC Delco plugs gapped at .040, and new wires from AC or Napa premiums. Smoothed my truck out very nicely.

[Wires]

I have a 2007 Silverado classic With a 5.3. From Day one The Truck seems to have a misfire but Not bad but noticable. The past month has been really Bad. But theres no check engine light at all. It can be felt at a stop light idleing, some times the RPM needle will boune around a bit, and you can fell it if you were to lean on the truck. I have plugged it into my cheap obd2 scan tool theres no codes that come up. I have taken it to 2 different dealers, they have also Plugged it In to there scan tool, They say theres nothing we can do if there no codes. This past week i have put back the stock air filter, and exhaust, that made no differece. The only thing that i can think of are the spark plugs, plug Wires, coil, Or injectors. The truck is never driven hard or pulled anything, I use Chevron Or shell 89 gas, all different gas stations, I never let the gas tank go lower then 1/4 tank. What else can I do? Is there anything i can do?

 

I was looking into use seafoam, And 3m Fuel injector cleaner. And doing a basic tune up. Changing plugs and wires also testing the coils.

 

Thanks for any help.

 

Was the A/C running more than normal lately? At idle with the A/C on I get a shutter from the engine when sitting at a light and in gear. It caused by the EFI running the engine lean for emissions and the idle super low. It happens all the time on my 5.3 and my 6.2, but more pronounced if the A/C compressor loads down the engine at the same time.