No compression in this cylinder, but ring seems to be still intact at hole. Can I replace the piston and just put oversized rings? I was planning to do this for all cylinders. Going to measure them soon, top of cylinder has lip from wear/but its very small.

Also, valve job or just clean the carbon off and call it a day?

Oops forgot to say engine has 180k on it and never been Overhauled or had valvejob.

Thanks for the help guys,
Tom

 

Yikes!!

Considering the condition and the mileage I would say it's due for a complete OH; top and bottom end!!

I would ck the knock sensors while you're at it; that piston could have been damaged by chronic detonation.

 

gdog, what do you think could of caused the detonation? The guy before me said he polished the turbo inlet and exhaust, would this cause enough to either mess with the Air to Fuel ratio to cause detonation?

Also, I found a set of used pistons, 'D' size as well. It is from ebay though...

http://cgi.ebay.com/ebaymotors/1994-...Q5fAccessories

 

Thats the biggest picture I have ever seen

 

That's what she said! ;-)

 

These engines have knock sensors to prevent detonation (by adjusting the ignition timing); if they're not working then.... hence my previous advice.

BTW: hard to tell from this pic if that was caused by detonation/pre-ignition or what-not; get the piston out of there and take a closer look.

Polishing the exhaust is usually OK. Polishing the intake is usually NOT OK, unless you really know what you're doing and flow test your work.

Used pistons??? You usually get what you pay for...

 

I doubt is detonation, the guy before me knows his stuff and said no CEL or pinging, he says its running lean. This was right after he rebuilt the turbo and polished intake.

If I'm in specs, yeah, used pistons and rods with half the miles. He said he polished the INTAKE to the turbo, so am I in trouble? If my AFR is too lean, could this also be caused by dirty, old injectors not delivering the fuel specified by the ecu?

Pozdrawiam

 

The 2 most common causes of detonation are either to much air/not enough fuel or improper ignition timing. It is possible that the AFR is off due to plugged injectors but I would think the knock sensor would have been able to notice a cylinder running that lean. Also the O2 sensors would have picked up the difference in the EGT's. Please correct me if I am wrong but it also could have been caused by a decent vacuum leak.

I personally would not purchase used rods without having a professional machinist look at them and measure them to ensure they are within spec. If they are out of spec (within reason) they can be machined back to spec.