One stupid question, hope you don't mind. Why would a sticky hydraulic tappet (or tappets) will cause a misfire or backfire upon acceleration? Any point of view is welcome.

 

Because the valve is not fully opened

 

I had this precise problem. Upon VERY hard WOT acceleration, my CEL, PSM and ABS lights would occassionally come on. The ABS and PSM would turn off shortly thereafter, but the CEL would stay on. The CEL code corresponded to a misfire -- not misfiring, but rather, only one or two misfires. Upon tearing my engine apart, Stephen discovered that I had a broken tappet.

Craig

 

Dear Stephen and Criag, thanks for your reply. However, I am wondering if you could give me a fuller picture of why a sticky valve not fully opened would cause a misfire or backfire upon acceleartion. Thanks again.