3100 Burnt Valve?

[Bastogne]

I own an 03 Grand Prix SE with 134K. Just bought the car in September. I was driving to work Sunday night and pulled out to pass a car. As I'm passing, the Check Engine light starts flashing. It runs fine the last 10 miles on the highway but when I get in town it is running like crap. Pull into O'Reillys and they say it is throwing a Cyl 4 misfire code. I limp it home the next morning and to the shop. They say it is only throwing the generic P0300 misfire code. They have it in the back for a few minutes and the guy tells me that I have a burnt valve. He says he came to this conclusion because he stuck his hand over the tailpipe(?) and it sucked his hand back up to the pipe.

They are telling me I am better off cost-wise dropping a used engine in rather than have the valve issue fixed.

3 Questions:

Is that the best route to take?

Is his hand-over-pipe technique accurate?

What are things that could cause a burnt valve?

Thanks for any help you can offer.

[Superdave]

He's an idiot, take your car to another shop immediately.


It's very common for the injectors to act up in the later gen3 engines, if it's a cyl 4 misfire then reach through the plenum with a long screwdriver and smack around the middle injector. That usually fixes it.


It could also be a bad plug or plug wire, if in doubt take it to a GM dealer service department.


BTW, welcome to 60v6!

[Bastogne]

I changed the plug and I have spark at both ends of the plug wire. I smacked the injector around a little bit but no change. It looks like there is gas seeping around the middle injector...or maybe condensation on it. Would a Fuel Pressure test tell me if I have a leak?

[Bastogne]

I've got a bad rocker arm on #4. Stripped the threads all the way out.

Thanks for taking the time to try and help.

[Superdave]

Wow, that's unusual.

time for a helicoil and some loctite red.

[Joseph Upson]

He says he came to this conclusion because he stuck his hand over the tailpipe(?) and it sucked his hand back up to the pipe.

Now, that's funny. I guess a discussion about the scavenging effect would be wasted on him.

[Jonpro03]

I LOLd