Dead cylinder

[Pomorza]

Hell all

This past morning I went out to start the Z. Outside temp was about 90 - its Arizona its hot. Car started fine but it runs on five cylinders for the first 30 or so seconds and then is fine. Anyone have any ideas before I go head long into figuring this out? It did it once more when I started it this past afternoon - after sitting for ~7 hours. Again cleared up after a few seconds. Doens't seem to lack power.

Thanks

Jan

[siteunseen]

Maybe a fouled plug burning clean after a few seconds?

[bartsscooterservice]

old spark plugs , spark plug wires,rotor,rotorcap/ignition points ?

[Wade Nelson]

First I'd diagnose if it's an ignition or a fuel problem.

Try starting it with some added faux fuel (starting fluid, ether, brake cleaner....) If the problem clears up then that cylinder probably isn't getting sufficient fuel. Start by changing the fuel filter, and next put a fuel pressure gauge on it to see what's going on. Check the connector to the injector.

Next I'd pull the wire off the spark plug of the affected cylinder, stick a screwdriver in it, and let it arc to ground. See if you're missing spark on that cylinder in the first few moments after startup.

If neither of those help you DIAGNOSE the problem, then I'd pull the spark plug and squirt some oil into the cylinder. Put the plug back in, and start it up. If it runs fine then you probably have shot rings in that cylinder and you don't have compression there until oil starts circulating and the cylinder walls get "wetted." Or you could stick a compression gauge in that cylinder and take readings after it's warmed up and running, and then let it sit till cold and repeat.

In any case you should be able to diagnose this problem in 10 minutes or less, provided the engine is (currently) cold.

Edited June 1, 2013 by Wade Nelson

[Pomorza]

Thanks for the reply guys,

Wade: Wouldn't a shot ring (or rings) cause smoke of some sort as they aren't sealed correctly?

[FastWoman]

If you've got any varnish in your engine, you might have a hanging valve. I've never had this problem on an interference engine, but that's not to say it can't happen. Might also be rings. Might also be a dribbling injector and a flooded cylinder (flooded after engine shut-down from the residual pressure in the fuel rail). I'd say the conservative approach is to take some stone-cold compression readings. It wouldn't take very long. I think I'd do the following:

1. Start the engine, observe that it's still running on 5 cyl, and then shut down immediately.

2. Pull the plugs and examine them. Is the plug for the offending cylinder fuel-soaked or caked in carbon? If so, consider a fuel issue.

3. Compression test.

4. If all looks normal, then consider ignition issues. Swap the plug and wire of the bad cylinder with the plug and wire of a good cylinder. Did that transfer the problem to the (previously) good cylinder? If so, replace plugs and/or wires. (Of course you could also have a bad cap.)

[Pomorza]

Guys and gals

Thank you guys for all the suggestions. This weekend I pulled all the plugs out one by one and examined them. All but one had an orange color to them (#1 was white). The #4 plug had a lot of carbon deposit on it which I cleaned up using wire brush. Rechecked all the gaps. I also richened the mixture since it was running lean - based on my wideband readings. Started the car up and it runs like a top.

Thanks again

Jan

[Wade Nelson]

So #1 is running lean and #4 is running rich. Sounds TO ME like it's time for a new set of injectors.