2000 Chevy S10 P0446 and misfires

cwatkin
Sun, 26 Feb 2023 20:45:25 +0000
Maintenance/Repairs

A check engine light recently came on for code P0446 on my 2000 S10 4.3L. I have one of the cheapo code readers that plug into the OBD port and that is how I read the code. The simple solution would be to throw a $30 evap vent solenoid at this but I am not sure that is the problem.

The truck recently went in to the shop for three things that might play into this, both at the same time. I had the fuel pump replaced. The fuel line coming out of the pump was leaking and spraying fuel all over the top of the tank. There was a noticeable odor of course and that is why the truck went into the shop. The dreaded intake manifold gasket had been leaking coolant for a while but was manageable. Then is seemed an injector was sticking open so I had both the intake gasket and fuel injection spider replaced. So it went in for fuel related problems at the tank and at the injectors. Obviously all the stuff on top of the intake had to come out.

The truck runs fine throughout 99% of driving conditions but has two obvious issues. There is a noticeable misfire at idle. You can hear that poofing sound out the exhaust while it is sitting and idling. It is fine under normal acceleration and driving. The other issue is at high throttle/high power conditions such as when accelerating quickly or passing. The engine will cut out and lose ALL power, creating a strong bucking feeling. It returns to normal when you let off the gas.

I have felt like the HVAC system switches modes such as from normal to defrost or the temp changes when climbing hills as well. I know these are vacuum controlled so am wondering where to start, especially considering all the variables that might be in play here.

I am not getting any misfire codes or pending codes for misfire. It has been driven several hundred miles since this started so shouldn’t be an issue with not enough start cycles or mileage.

I checked the vacuum lines and wiring connections . There weren’t any any obvious problems. I figure I will pickup a can of starter fluid to spray around the lines and see if I can notice a difference in how it runs to detect a vacuum leak. It seems to run fine when cold but starts misfiring and sputtering at idle once warmed up. It isn’t a high idle or anything with a lean misfire like you hear with vacuum leaks.

Is this possibly just the vapor canister purge valve? I figured this wouldn’t cause running issues and just create excess emissions. I have been told to just replace the gas cap because these are cheap and that might be the issue. The seal on mine looks fine but this might not be a bad idea. I don’t see this causing the misfiring I am experiencing though so want to narrow this down before throwing money at it.

33 posts - 5 participants