Rough running 2005 Impala 3.4

CEL codes P0306, P0300B, P1811C

Rough running, 140K, jerky shift on occasion, no acceleration

95K changed plugs, all filters, fluids, etc.

takes forever to accelerate, missing all the time, slower works better — no power to pass, significant mph loss on hills

Has the fuel pressure been tested?


Are those codes correct?

Has the throttle body been cleaned?

I’m going to try.

P0306 - Misfire detected - cylinder no. 6

P0300B - unsure of the ‘B’, but P0300 is multiple random misfires.

P1811C - again, unsure of the ‘C’, but P1811 is a transmission code for ‘Maximum Adapt and Long Shift’. I read that as a communications problem between the ECM and TCU, usually happens with some P03XX codes, since the TCU requires shared data from a lot of these sensors.

I think Tester is right, and get the fuel pressure tested. Also, have the ignition system evaluated, especially the ignition module and the coils.

Why has the use of a scope to look at secondary ignition patterns fallen out of favor?On “tune-ups” in the 70s-80s we always “scoped” poor running engines.Must have something to do with the diagnostic capabilites of OBD2.Does anyone scope engines any more?

yes we graph them,same thing,with a new twist.

scope takes too much time,and new guys would not know a fireing line from a dwell line.

that help?

Thanks BK. Those letters after the numbers threw me.