Okay here goes. I've been having my check engine light coming on about once a week, after resetting it obviously. I took it to the shop and they pulled a misfire code out of it. Well they run the usual diagnostics and they come back to tell me that one of the pistons is not holding pressure and that it is a possible bent valve. Okay not quite sure how that'sgoing happen as I can't even remember coming close to a real over rev situation on the upshift but hey anything is possible. So they get the head off and low and behold no strike mark on the piston and the valve looks good. They are sending the head to the machine shop. Okay wise ones educate me. Is it still possible to have a bent valve with no indication on top of the piston? Is over reving even possible with a S2000? Broken ring? If so wouldnt I be getting a little smoke. Help!!

 

Okay I did a search for the situation I listed above and yes there are tons of situations out there dealing with my problem. Now it raises another question, I noticed some people get it covered under warranty and others do not. Anyone out there have this situation and get it covered under warranty? If so PM me and let me know, I might need some horsepower to get them to cover it.

 

If your valve and piston have no signs of contact, then it is unlikely that you have a bent valve. The only way to overreve this engine is to miss a shift. It appears that the reduced compression was not due to a bent valve.

There are a couple of sources of reduced compression: lost pressure at the valves, or at the rings. Yes, a broken ring would give you compression loss, but I find this unlikely. How does the cylinder look? Is it scored? Is it possilby your #4 cylinder?

A blown head gasket would also cause you to have reduced compression. There would be telltale signs of this when they removed the head.

If it's a scored cylinder or a blown head gasket (and you're not FI), you have a pretty good case for getting it covered under warranty.

Good Luck!

 

Yeah thanks guys. Yup no mark on top of the piston and I haven't had any smoke from the exhaust so I'm pretty sure it's not a ring. They have the head at the machine shop right now and I'll let you guys know. Yup it's the #4 piston.

 

what yr is the car and how many miles do you have? does your car see 9k rpms often or not?> did you feel a vibration on the steering wheel when this was going on or not?

 

What is the machine shop going to do with your head? It doesn't sound like they have a diagnosis yet, so what would they "fix"? Did they check the block for scoring?

 

exactly, everything is sounding fishy to me.... why would they just send if off so quickly, and you still dont know whats wrong..... also..... you have the supercharger dont you?

 

No, no supercharger on the car. Yeah the car has seen 9000 a few times but only bounced it off of the rev limiter once that I can remember. Never had a vibration that I could feel in the steering wheel. Yeah I'm suspicious too as my service advisor told me once they got the head off that they couldn't see anything wrong with the top of the piston and it looked as if the valve was seating fine. Well I questioned the reasoning behind the head being sent out and the possibility of a broken ring but was advised that they wanted to start with the small things and not dive into breaking the engine down or opening up the bottom end. Well so far I haven't heard anything and it's going on two weeks. So I'll keep everybody up to date. I find it funny that right off the bat they screamed over rev. You know I know that Integras, NSX's, RSX's aren't as high winding as our cars but I know they don't have the recurring problems that alot of people seem to be having. Car has 31,000 on her.

 

i thought i remember seeing earlier posts from you about your supercharger etc a long time ago?

 

Was it the #4 cylinder?