I just bought a 1996 Mazda B4000 4x4 4.0 ohv, runs good but had cel
p0401. The previous owner blocked the egr
valve off with a metal plate where the gasket should be. I removed the plate and installed a new gasket, started the truck and it idled really rough or stalled. I also noticed the pipe that goes from the egr
valve to the upper intake manifold did not have the correct o-ring on it causing a vacuum leak. My question is, why would it run fine with the egr
blocked off, when there is a vacuum leak at the intake manifold? Does that mean the egr
valve is bad and the vacuum leak is not the problem? I'm just trying to pinpoint the problem. My plan right now is to replace the upper intake gaskets, egr
valve, dpfe sensor, and the egr
vacuum solenoid. But, I would rather find the problem part and just replace that. I hate throwing parts at it until its fixed, but I'm stuck.