Ericy321

If the one you pull has an effect thats good. If it has no effect then there is in issue with that cylinder already.

AGreen

Don't pull the plug wire, use the vacuum tube/test light method that is much safer. laugh.gif

But yeah, what I'm expecting to see is no change from 1&2, since they're the low compression cylinders as determined by your testing. If you ground the spark to cylinders 3 or 4, it's probably going to stall, since the car's probably only running on those 2 cylinders anyways.

So essentially what you're doing by conducting this test is removing cylinders (one at a time) from the power-production for the engine. Grounding the spark effectively kills that cylinder, so by monitoring the way the engine runs when you ground the spark, you can determine which one's giving you problems.

Edit: Just buy a freakin head gasket already! We've already determined the problem, this method's just a dead sure-fire way of knowing your motor's jacked up. Start ripping the head off. Take off the valve cover, timing belt cover, cam bearing caps, cams, drain coolant and remove hoses, unplug all sensors from the head, remove the 2 14mm bracket bolts on the back of the intake, pop off the exhaust manifold, pop off the brake booster vacuum line, and there's a little vacuum tube that runs to the firewall, pop off throttle linkages and heater hoses, remove the intake pipe, and unbolt the cylinder head. There's 10 head bolts all together, and you'll need a M8 and M10 hex head socket to pull those out. On average, pulling the head takes about 1-2 hours. 3 hours max.

97DerekTiburon

OK, this is stranger (but good, maybe?)

I started my car tonight (my whole family has the ROTA vurus so I've not been able to do anything). I had the hood up and like an ass, touched the #1 header tube and left some skin on there (nice smell BTW). I learned a quick lesson and spit on #2 and it flew off like a coal stovetop. #3 & #4 were much cooler (what I had expected and why I touched #1) so I decided to grab some insulated pliers and pull the plug wire out of the head on #4... NOTHING CHANGED (kept running like crap). Same thing with #3. I did #2 and it almost died but I stuck the wire back on quick enough. Same with #1.

I then disconnected #4's injector harness and it didn't change. Did that with #3 with no change. But it started to die when I did #1 and then #2.

I'm guessing that #3 & #4 are not getting fuel or a signal to pulse.

What would be my next diagnosis? Remember that this crappy-running condition was intermittant and that I had pretty low compression on ONLY #1 and #2 which are firing perfectly and my car even running like this blows absolutely no smoke upon startup no smoke with regular driving or full-throttle. So I'd think valves and rings are good.

I'm guessing I f-ed up the compression readings somehow on #1 and #2.

How exactly is the injector test performed? I don't know if it's a fuel delivery problem on only 3 and 4 or if it's an injector signal problem on only 3 and 4.
'

AGreen

dunno.gif

Hmm... this over-the-internet diagnostic thing isn't easy at all!

Re-do the compression check, and make absolutely sure that's not the problem. Now, when you do this, you'll need to follow some guidelines that I don't think I mentioned before.

-Remove all spark plugs
-Disconnect the crankshaft position sensor (to the driver's side of the exhaust manifold, in the block)
-Fully open the throttle valve
-Install the compression gauge, and crank the engine about 5-6 times, or until the needle stops bouncing up. It will bounce up quickly, then very slowly climb. When it only bounces up about 1 psi per revolution, stop.
-And make absolutely sure that the compression gauge you're using is sealing properly.

You're absolutely sure that there is spark at all 4 cylinders, right? And if you've verified that's all ok, use the test light method to check injector pulse. If all that's good, check that the injectors are flowing. You can use a baby bottle with a nipple on it. Remove the injectors and stick each in a baby bottle. Hook the wires up, and keep the injectors attached to the rail using zip ties. Re-attach the CKP sensor and crank the car. Each injector should spray (obviously) and you can actually measure the flow each one does. The good thing about using a baby bottle is that you can see the spray pattern too.

I'm still leaning towards shot compression dude.... and out of curiosity, when you say #1 cylinder, you *are talking about the cylinder closest to the passenger's side, right?

97DerekTiburon

I'll do all that tomorrow, thanks.

Yeah, this IS getting kinda crazy but it's my fault for being so quick to assume things only to have them not be what I thought.

No, I was saying #1 was drivers' side but up 'til now, it wouldn't have made a difference because I've been consistant... consistantly WRONG wink1.gif