Cylinder drop test help

[fcukwithmeprelude]

Hey I'm pretty new on 3geez, I do most of my work on preludes and preludepower.com.. Anyways. I have a customer that has an 83 accord. When I got the engine started, it felt like it was running on three cylinders. So I did a cylinder drop test (pulling one spark plug wire at a time) and sure enough cylinder 2 wasn't putting out. I let the engine get up to operating temp and I did the test one more time just to make sure. And, this time when I dropped cylinder two, the engine started running a tad bit rougher. I put the wire back on and it smoothed out.

Soo, I thought about it for a while and couldn't really come to grips with what was going on. I let the engine fully cool down and I did the test again. I started the engine up and with it cold, I dropped cylinder 2. It made NO difference what-so-ever if I had the wire on it or not. Then, after it warmed up cylinder two was firing and if i dropped that cylinder the engine would let me know it needs it.

Anybody have a clue as to what's going on? I thought that maybe there was something that was expanding when the engine got to operating temp to allow good enough compression to make it fire only when hot, but not when cold.

I'm going to perform a compression test in just a little bit and also check over the ignition system but any advice in the mean time would be great. Thanks.

[2ndGenGuy]

Almost sounds like a leaky head gasket. It could be that water is slowly leaking into that cylinder while the car sits, but its not enough to notice while its running because its burning it off.

I guess though that you'd see a fair amount of water burning out the pipe...

Car's not smokey is it?

If you drop a different cylinder while the car is cold does it run even worse? Like does it seem to add to the problem?

[fcukwithmeprelude]

Almost sounds like a leaky head gasket. It could be that water is slowly leaking into that cylinder while the car sits, but its not enough to notice while its running because its burning it off.

I guess though that you'd see a fair amount of water burning out the pipe...

Car's not smokey is it?

If you drop a different cylinder while the car is cold does it run even worse? Like does it seem to add to the problem?


Indeed, if I do drop a different cylinder the engine does run worse.

I have reason to believe it's not the head gasket because of multiple compression tests hot and cold, and due to the fact that I have yet to see any puff of smoke come out the exhaust. This car really amazes me for the fact that it doesn't burn ANY oil and I don't see any white or black smoke either. It's a one-owner car that's been well maintained. About 220,000 on the odo.

[2ndGenGuy]

Well if the compression seems good, the only other things I can think of are either you've got some wierd spark issue, fuel issue, or a stuck valve.

I don't know if you can get a valve that sticks closed or not that wouldn't screw up the rocker arm or camshaft.

Seems to me that it's most likely some sort of fuel issue. Wish I could help you out more...

[w261w261]

I'd put in a new plug in #2. Maybe there's an issue with the center electrode that allows it to work when hot.

[fcukwithmeprelude]

Don't ask me how, I have no idea how this works out.

I've worked on the car all day now and it seems not to be doing that running on three thing any more. The carb's second barrel isn't doin anything so I think I'm going to buy a rebuild kit for the carb tomorrow and get to work.

And it's got brand new plugs, wires, cap, and rotor.

[88Accord-DX]

Maybe points, reluctor, something in the distributor. Not familar with early 80 style motors. Try a leak down test with compressed air when the cylinders are at TDC also. Reminds me of valve having carbon deposites on it & sealing after it gets hot. Also, intake gasket leaking can cause similar problems sometimes, but rare.

I HIGHLY doubt you have a ignition controle module, but do check Ohms resistance on the coil to rule it out.

[Ichiban]

82-83 cars do have a "module" of sorts, the ignitor that is mounted on the firewall. these are solid state and rarely if ever fail. I would suspect plugs, wires and cap/rotor first. I see that they've been replaced, but I've gotten bad brand new plugs before. what does the plug in #2 read like? Check for fouling (oil or fuel) or damage (cracked insulator, gap, short to ground), test and then replace. If you have an inductive timing light you can verify ignition while the car is running hot/cold without pulling the wire off.