How do I find out which cylinder is misfiring? Apparently an exhaust valve is "burnt, cracked"

one of the geniuses on this site told me to pull the injector wire for that cylinder before I drive it like it is, which I'm going to have to. I think this is a good idea if it works. But how do I tell which cylinder has the problem? If its closed and sealed I dont think it'l be a problem but if its open/unsealed, well I don't want unburned fuel going out the tail pipe.

is there any way to tell which cylinder has the valve problem before I drive the car? I do want to pull the injector for that cylinder to protect the catalyst and prevent noxious fumes.

 

pull the head, sounds like you're going to have to anyways

 

**** I should've paid more attention when I was typing.

I hope I'm gonna throw this lil thing in a scrap pile, I'm gonna clarify the OP

 

First, how do you know you have a burnt/cracked valve? Who told you? Highly doubt that's the issue... First thing, while the engine is running. Pull one spark plug wire from the spark plug at a time. If the idle drops or is affected, it's not that one... If there is no change, then it's that cylinder. Either no spark, no fuel or no compression...

 

i have personally dealt with two b7's with burnt valves. not impossible at all.

 

This is a good way to roach an ignition coil, don't do it. You'd be safer unplugging injectors.

OP if you have a random miss fire there are several possible causes. If your running on 3 cylinders unplugging injectors to find the one that makes no difference would point to the problem cylinder.

Or compression and leak down test if you suspect a burnt valve.

 

a compression test would be ideal, it is quick, cheap, and you can do it on the spot.

 

I'm looking at the car for the first time tomorrow. If it isn't too rusty, I'm gonna take it, IV wanted a DX coupe since a week after I got my EH9.

I think I'm gonna bring a compression tester, and if the bad cylinder has low compression from the valve not sealing, ill know. Iv gotta drive this thing bout 50 miles to get it home, ill drive it on 2 cylinders if i gotta. Now it actually a good idea to disconnect that injector from the bad cylinder when im driving it, to protect the catalyst and the environment?

the owner told me when it didnt pass emissions he had a mechanic look at it and they diagnosed it as a messed up exhaust valve. I'm not trying to actually repair this lil POS engine, id rather scrap it and replace it with another Z6 if not a b series

 

Make sure you unplug the distributor if/when you do the compression test. If you don't you may go from a dead cylinder to no spark at all and you won't be driving it at all.

Don't trust what the seller tells you their "mechanic" told them. Be prepaired for anything including towing it if you really want it.

 

I got no means to two it. I have access to a dolly, but no freakin truck.

if he mislead me when he said it'l run and it isn't too rusty ill be ******* pissed, I gotta drive 4 hours tomorrow for this car if I take it or not. I spent months looking for one of these with a bad head gasket. More than half the cars IV seen were accidently worse than Rice Police's DD, and even tho I dont want an accidently car I inquire on the price and these crazy SOBs want 2,000+! Screw that I want a shell.

 

I'm probably too late by the looks, but pulling the spark plugs will tell too which is the bad cylinder. If one is misfiring the plug will tell by not being a pretty tan color.

 

Thanks tomcat, I'm leaving in a little bit. Since ima do a compression test ill look at the sparkplugs too