dead cylinder? bad valve? HELP!!!

[ssnnooppyy]

yes, I have searched the board, and no, I haven't found "exactly" what I am looking for. I have a 90 240 with a k&n, 2.5 inch catback with a flowmaster, and that's it. I replaced te injectors a while back, and today replaced the cap and rotor and wires and plugs. The #3 cylinder seems to not be firing properly, if at all. I took off the oil cap, and air came rushong out like a tornado. I don't have the capacity to do a compression test, but I was told that the air rushing out was a tell-tale sign of a stuck valve. The engine idles like a bucking bronco, and has zero power. Sounds like a potato in the exhaust pipe, lots of sputter. No smoke, no leaks, not using oil, injectors not leaking, plugs good. Any insight? Any "shortcuts" on diagnosis?

[DAEDALUS]

Interesting...so I'm guessing by stuck valve, you mean that the exhaust valve is stuck in the closed position? And the blow-by is pressurizing the crankcase? A compression test wouldn't help, then, would it? Unless the valve was stuck in the open position, but that wouldn't explain the crankcase pressurizing. And the piston would probably have hit the valve already. Either way, it might mean that you've destroyed a couple cam rockers and/or some bearings. I think a valve cover removal might be in your immediate future. I'm sorry I can't help more, but I definitely want to hear the outcome on this one. Get it fixed fast before you start blowing seals and gaskets.

[ssnnooppyy]

Ah, the old remove-the-valve-cover routine, eh? Sounds great to me! So, lemme ask this... what exactly should I look for? I figure if it's something major, it will be a no-brainer, but will something like this show by a visual inspection???

[ssnnooppyy]

Oh, I take the number three plug wire off, and nothing. No change. But I take off any other plug wire, and the engine heaves like a p0rn-stars boobs! (up and down, bouncy boucny!!!!)

[DAEDALUS]

Well, if the valve is indeed stuck, then it won't be moving as you turn the crankshaft by hand with a ratchet (socket on the crankshaft bolt). You'll see the camlobe go round and round, but the valve will be fixed, which is why I say that you've busted the rockers and/or damaged the cam bearings. Now, that's just to figure out what's wrong. The REALLY bad news is that you'll probably end up pulling the head.

[ssnnooppyy]

Kewl. I am giddy with all the excitement. I thnk I will pull the valve cover tomorrow, and then throw the car off a cliff. Wanna buy a 90 240 with a rumbly engine??? I do most of the work on my car myself, the injectors, the simple stuff. This scares me. I have a good mechanic shop to use, but like bad mechanics, the good ones are expensive. Thanks for the info, and I'll post when I figure this mess out.

[ricebike]

just a dart... how about switching the plugs & probably test the # 3 plug wire... that's easy enuff b4 u haul the car off the cliff...

[ssnnooppyy]

Ya know, I had put new plug wires on, along with the cap and rotor, but I never thought to switch the plugs!!!! Here's a dumba$$ question... can a plug just "go bad"??? I took the plug out and bisually inspected it, you know for deposits or mechanical induced damage, and it looked like a two week old plug. Switch the plugs..... hmmmm.....

[yellow_jacket]

You really need to go by a compression gauge at sears or something. They are not expensive(~$50) and it is very easy to do.

DAEDALUS is right about the valve. The only way it could get stuck is if it is stuck down. The DOHC motors have solid lifters so it can't get stuck up. There is also a slim chance the cam lobe wore off. Here is a list of things you can try to get this fixed.

1) Check the compression2) Check for spark at the bad cylinder.3) Swap plugs and wires with a known good cylinder.4) Check the cap for cracks or arcing(would cause a no spark condition on the bad cylinder.)5) Check the fuel injector wires(jiggle them and make sure they are plugged in all the way)6) Swap fuel injectors with a known good one.

And yes, plugs can just go bad.

[ssnnooppyy]

Awesome. I will try the switching plugs first, then the compression test (I think I can get my hands on a friends gauge), then I'll pull the valve cover.... The injectors all squirt okay, the plugs are all snug, the spark is okie-dokie, and the wires, cap, rotor are brand new (less than 24 hrs.!) So hopefuly it is the plug.... first I'll pray real loud and long, then I'll grab my tools.....

[ssnnooppyy]

So here's a sick irony from the gods of autos.... I got all ready to start in on the old 240, when a rush of wisdom set itself upon me. I thought to myself "self, you should start the car first". I did. It ran fine. I started it again. Let it run for a few minutes. It ran fine. I am still gonna pull the cover and peak around in there, but this is just getting weirder and weirder. Perhaps while it runs smooth, I will attempt to sell it, and get a newer model of this car I have come to love and adore (if you can do that while wanting to kill it!) =)

[ssnnooppyy]

Yup, I drove it out the neighborhood, and she croaked. I pushed her home, started tearing in to things. Long story made short, it was the #3 fuel injector. No flow, but it showed continuity. Now she runs smooth, but hesitates when I give her some throttle. At speeds, she does fine. At takeoff, she's a dog!!! Back to the drawing board..... Is it possible I did some other damage by driving with thtat cylinder not firing??? I am gonna post that question as a new thread... hopefully this will end.....

[I am Technoman]

Is youre kat clogged ? take the pipe down and see how it runs.....

[ssnnooppyy]

runs the same with or without. I have a 2.5 inch catback flowmaster system, and was told that I could have problems 'cause of that. I kinda doubt it, but who knows. She seems to surge around 1500rpms. If I floor it, she lurches forward very slow. If I feather the gas, she accelerates better, but still chugs and surges. ?!?!?!?!?!?!?!?