There is actually a TSB(technical service bulletin) on this. Although they are trans codes, this is usually due to the valve seals and valves that cause a misfire.
Here is a bulletin from GM .
#05-06-01-030D: 1.6L L91 Intermittent Misfire During Deceleration or Steady State Highway Driving After Cold Start with DTCs P0300, P0700, P1781 and/or U0401 Set (Replace Valves and Valve Stem Seals) - (Sep 12, 2007)
|Subject:||1.6L L91 Intermittent Misfire During Deceleration or Steady State Highway Driving After Cold Start with DTCs P0300, P0700, P1781 and/or U0401 Set (Replace Valves and Valve Stem Seals)|
|Models:||2004-2007 Chevrolet Aveo|
|2005-2007 Pontiac Wave (Canada Only)|
|with Eco-Tec II 1.6L Four Cylinder Engine (VIN 6 - RPO L91)|
|Built Prior to VIN Breakpoint 7B797231|
This bulletin is being revised to add a VIN Breakpoint to the Models and update the Warranty Information. Please discard Corporate Bulletin Number 05-06-01-030C (Section 06 - Engine).
Some customers may comment on an engine misfire on rare occasions. Typically, misfires related to this valve sealing concern will be very intermittent. The intermittent misfires may or may not be felt by the driver and they will normally occur during engine warm up, deceleration, highway driving, wide open throttle acceleration, and/or uphill driving.
Additionally, DTCs P0300, P0700, and/or P1781 (2004 models)/U0401 (2005 models) may be set. If a brief engine misfire occurs, it is possible that a P1781 or U0401 DTC may set without the presence of a DTC P0300.
The engine misfire may be experienced due to a valve sealing concern.
If this concern is experienced, perform the appropriate SI diagnostics. If the SI diagnostics do not isolate a cause for the concern and the last 8 digits of the VIN are:
| ||Important: On vehicles built prior to VIN breakpoint 5B406012, check GMVIS to see if the intake valves have already been replaced with the current P/N. If the intake valves have already been replaced, replace only the exhaust valves and valve seals. |
| • ||PRIOR to 5B406012, replace all 8 exhaust valves, all 8 intake valves, and all 16 valve seals. Refer to Cylinder Head Disassemble and Cylinder Head Assemble procedures in SI.|
| • ||AFTER and INCLUDING 5B406012, replace all 8 exhaust valves and all 16 valve seals. Refer to Cylinder Head Disassemble and Cylinder Head Assemble procedures in SI.|
Seal, Valve Stem Oil
Edited by eric on 2/19/2011 at 5:00 PM EST