Running on 5 cylinders
 

My car was running perfectly yesterday. The motor was rebuilt recently. Plugs wires, distributor cap and rotor are new. I disconnected and reconnected 1 or 2 plug wires. I could feel them snap in place. Now the motor is running on 5 cylinders. I've checked the plug connectors. They are all tight. How can I figure out which cylinder is causing the problem?

Got two wires crossed? Recheck firing order.

Never had two wires off at the same time.

Easiest thing to check though a long shot is for a defect in the cap at one of the terminals

Any chance you broke a spark plug on install? I'd suspect them then a bad wire. Real pain, isn't it - especially on one of these... pull all plugs and look for the one covered in fuel, swap in another plug and see if it changes. Make sure you have a good insulator in your plug socket. I busted off a brand new Delco plug recently in one of my other cars, must have been bad-in-box.

If it's the plug, I think I know which one. I'll pull it tomorrow & take a look.

Took off plug wires one by one. Resistance varies from 1+ to 7+ ohms from the shortest wire to the longest (these are Magnecor 2.5). Is this normal? The plugs have only been in the car for about 350 miles. No reason to suspect them. I checked one, and it looks perfect. Checked dizzy cap & rotor. Both 350 miles old & perfect. How would I know if my airbox is cracked? How could I check to see if it's a fuel problem. Definitely feels like one cylinder is not firing. If I rev the engine, it is not smooth or torquey.

More suggestions from the experts please!

My engine suddenly felt like it was running on 5 cylinders. Idle was OK, but no power. Pulled plugs and found one wet. Electrode was shorted by a piece of black who knows what. Cleaned up and reinstalled. Runs great.

In a dark garage, run the car while looking at all plugs. Look for any flashing in the engine bay. I still think you broke one on install if car was OK before.

Broke one what? I haven't installed anything.

You said you put plugs in.

You'd need to be pretty careless to break a spark plug when installing them, unless of course you dropped one on the concrete before installing it? :confused:

Make sure ALL your leads have clicked onto the plug's (or dizzy's) terminal reliably and real tight. Double check them to make 100% sure they are nice and secure.

I've done it with the best of tools. Sometimes they are broken in the box and just need a little extra 'help' to snap off. You'd be surprised.

No. The plugs have been in for 350 miles.

One check you might try is to idle the engine. Have someone hold the throttle slightly open if you need to. Pull each plug wire off in turn. If you are indeed running on 5, the "bad" one is shown when the engine does not change when the plug is pulled.

Does this occur when the engine is cold or warm? Have you checked your fuel and control pressures and the WUR? It is probably plug/wire caused but may be coincidental.

One thing I did notice. I backdated the heater recently and neglected to tighten the bracket that the coil sits on. There is a ground wire attached to this bracket. It is tight now, but if it was loose, could it have caused any damage to anything.

[QUOTE]Originally posted by Paulporsche
[B]One check you might try is to idle the engine. Have someone hold the throttle slightly open if you need to. Pull each plug wire off in turn. If you are indeed running on 5, the "bad" one is shown when the engine does not change when the plug is pulled.

Safety question: Is it safe to pull and plug these in with the motor running?

[QUOTE]Originally posted by rs6er
[B] The spray bottle method is safer IMHO, just start the engine and spray the exhaust lines, you can easily see which cylinder is not firing.

[QUOTE]Originally posted by rs6er
[B] The spray bottle method is safer IMHO, just start the engine and spray the exhaust lines, you can easily see which cylinder is not firing.

[QUOTE]Originally posted by rs6er
[B] The spray bottle method is safer IMHO, just start the engine and spray the exhaust lines, you can easily see which cylinder is not firing.

[QUOTE]Originally posted by rs6er
[B] It works with cars that don't have the high voltage ignition.
You'll get a nasty shock unless you have thick rubber gloves and thick rubber boots and don't lean on the car/engine.

It sounds to me like the spark is jumping to the case instead of going thru one of the plugs.