If an engine misfires and you're at high revs (say 7000), could this lead to a valve breaking? I've noticed a lot of people recently complaining about misfires. My car is in the shop with a broken #1 valve and they're claiming that I overreved the car when I know that I did not misshift. Could a misfire lead to a broken valve? They didn't check the ECU codes before disconnecting the battery, so that's not an option...

InsaniT

 

I'm no expert...but, I believe they must prove it is your fault before they can deny a warranty claim. Can anyone confirm this?

 

Not usually. Misfires are very common in cars and rarely result in mechanical failure....just inefficiency of combustion. Hate to say it but you probably did over-reved. Remember it was probably on deceleration and not acceleration. If you are positively sure you did not over-rev; insist the regional representative get involved and run "hardness" and "chemical" analysis on the failed valve. Metallurgical failure do occur but in a Honda the odds are against you.

But once again I'd say it sounds like an over-rev.

Utah

 

I thought the S2000 has a rev limiter. If so, how do you over rev?

 

Rev limiters only protect on throttle induced over-revs, not momentum induced over-revs. If you are at redline in 3rd and accidentally hit 2nd instead of 4th...you have yourself an expensive little problem.

 

Thanks, Utah for the advice. I'm sure I didn't overrev, though after dealing with this for the last 5 weeks, I'm starting to doubt even myself. I was talking to the shop foreman and he mentioned that if they took a look at the other pistons, there would probably be a mark on them from the other valves hitting them if this was an "overrev". Is that true? Is it safe to say that if those markings are not there that I have a decent case of it not being a mechanical overrev?

InsaniT

 

I think you might have a case if the other valves don't have evidence of hitting pistons. You might have one weak valve spring that caused the damage.

 

In simple terms, the rev-limiter protects you from over reving when you are going up the gears. But it can not protect you going down.

Bad things happen if you are in a high gear and shift down wrong. Say you're shifting from 5th gear to 4th gear but instead you go into 2nd because they are so close. Since you are trying to mate the engine speed and rpms of 5th gear with 2nd gear - and the two can not mate - so you get a broken engine.

 

About more than a month ago, I over revved my engine (I was pushing the car at that time). I did a 3-2 shift instead of a 3-4 shift, which really messed up the engine, considering the car was already at redline when I did this, ouch! The next day I noticed my car had a rough idle along with the engine check light. Immediately I took it to the dealership. They said that I had bent valves and bad fuel injectors on the #3 & #4 cylinders. They never questioned me, and they said it'll be covered under warrenty, and I was ready to deny that I over revved my engine! So after two weeks of my car being in the shop, I got my car back with new parts in my engine. When I picked it up, dealership told me that other S2000 owners also came in with the same problem, so I wasn't the first. I guess my dealership seemed pretty cool to me.

 

To everyone who read this, this is a very, very , very, very good example of what NEVER to write in an open and monitored forum.