Odd problem - Engine running rough

[MojoMoto]

Odd problem today. Somehow the fan and fan shroud came in contact - this resulted in a loss of the fan (3 blades), loss of the fan shroud and the hose that connects the radiator to the expansion tank was ripped out, taking the nipple on the expansion tank end with it.

I replaced the expansion tank, the hose, the fan and fan shroud. But now I have a couple of persistent problems.

One is that the temp gauge is all over the place. I think this is probably the result of air in the system that still needs to bleed out.

The other problem is more difficult to pin down. The engine now tends to run rough, as if its not running on all six cylinders. It will occassionally smooth out, and if I'm able to hold my speed it tends to stay smooth. However, as soon as I accelerate the roughness returns. I also noticed that if I ease off on the peddle a bit the engine will smooth out.

When I initially encounted the roughness, my first thought was a warped head. But the fact that the engine does smooth out on its own, and that I can consistently get the engine to smooth out by easing off the peddle makes me think that the head is probably ok. Now I'm wondering if something electrical got wacked by spraying coolant.

Any ideas?

[XOC]

Did you overheat or don't you know? Do you have milky-looking oil or oil in the coolant or "white smoke"? I'd think the water pump got messed up when the fan hit the shroud -- and even more likely - one or more belts.

[MojoMoto]

I didn't overheat when the incident occured. After I got everything back together I was getting wild swings on the temp gauge - full right, illuminating the red overtemp light on the gauge - and then back to center. I suspect this is due to trapped air passing through the system at the point of the sensor.

The coolant looks fine and there is no white smoke.

The water pump appears to be okay. It's turning smoothly and definitely circulating water. No leaks either. It just went in a few weeks ago so it is (evidently) pretty strong.

I checked for fault codes and I'm getting 55 - A/C Compressor. Not sure why, it seems to be working fine.

I'm going to pull the coils today and check for possible water damage. I'll also pull the plugs.

[MojoMoto]

After sitting overnight it seems most of the air made its way out of the coolant system. I bled it once more and now I'm confident I have the temp issue resolved. The temp needle stays dead center, the heater blows very hot and I can find no visible leaks. Everything looks good on the coolant side.

I pulled all of the coils and checked them with an ohm meter. All coils appear to be within spec although, I should mention that the meter never settled down, jumping between .2 - .9 ohms on all coils. I suspect that my Craftsman Multi-Meter isn't all that great (it may be time to get a Fluke).

The spark plug well of the number 5 cylinder was pooled with semi-liquefied copper anti-seize paste, which had coated the coil boot inside and out. This was the cause of the rough running engine. I don't know if this is in any way related to the loss of coolant or if its a separate problem that coincidently showed up at the same time.

After cleaning out the spark plug well and coil boot the engine ran smoothly. However, after driving about 15 miles the roughness returned, but only at the low end. Pulling away from a dead stop the engine was misfiring, but cleared up after shifting out of first gear. I pulled the number 5 coil again and cleaned the plug, plug well and coil once more. After my morning commute everything is running fine. We'll see how it goes tonight.

My visual inspection of the coils leads me to wonder whether on not they suffered any heat damaged. One has a small, hairline crack at what appears to be a seam at the base of the coil. Others have bumps or "bubbling" in this same location.

I've taken some pictures and posted them in a separate thread.