sticky tappet?

[superfans]

Car is 996. What will happen if the tappet gets sticky? Will it affect the A/F ratio and cause the vehicle to backfire.

[superfans]

Also, aren't those hydraulic tappets suppose to be maintanence free? Do you know how they can worn out or get stuck? Thanks in advance.

[Bill Verburg]

I assume that 996 will behave similarly to 993. On 993 they do go bad and will need to be replaced, it's a simple, fairly cheap procedure. When they go bad the make a clattering noise and performance is affected to a relatively small degree. But OBD2 is very sensitive to this and it is not surprising that a code would be thrown.

[superfans]

The story I've heard is that it is a very expensive procedure coz they have to take out the engine and the camshaft in order to get to the tappets.

I don't think the tappets are making a lot of noise at this stage (am I suppose to hear a ticking noise if the tappets are not working right?), but I was told that it is not functioning properly and thus affecting the A/F mixture causing the misfiring or backfiring.

[Bill Verburg]

I only know 993, when they fail they make a loud metallic tapping, like a miisadjusted manual valve(that's essentilly what it is!)

I can only assume that 996 will make a similar noise.

I can well believe that it is a far more difficult problem to correct.

[superfans]

Another stupid question, hope you don't mind. Why would a sticky hydraulic tappet or tappets will cause a misfire or backfire upon acceleration?