Possible misfire?

[peroxwhygen]

Good afterrnon, I recently purchased my first car, its a Nissan Micra Wave 1Ltre, 1994

I've noticed a problem which usually happens when im idle at traffic lights or accelorating in low gears, the car will just stop as if its stalled. The symptoms include irregular shaking and shuttering vibrations through the car when idle.

I replaced the spark plugs which where filfthy, this seemed to fix the problem for 2 weeks. I then removed the new spark plugs to find they where black like the old ones!!! So ive been cleaning them with a wire brush and putting them back in as a temp fix.

Does anyone know whats causing this problems? Any help would be greatly appreciated.

[ctwright]

Do you mean that the plugs were oily or more like dry carbon deposits?

[peroxwhygen]

They where mainly dirty deposits like black dirt or something but there was a small amount of oil on the threads it sounds bad doesn't it

[ctwright]

If you just had a little oil on the threads that may be where some was on your head from a valve cover gasket leak. If the rest of the spark plug was full of dry, black sooty stuff that is called carbon deposits. You should get another set of spark plugs and make sure that the gap is set correctly for them and then install them, and see if that helps. The Haynes manual says to make sure that they have the correct heat range. And too check for clogged air filter or problem in the fuel system and engine management system and also check for ignition system problems. Well, that doesn't help much I'm sure I know you probably wanted something more narrowed down a little.

If it was oil deposits instead you may have oil leaking past valve guides or oil leaking past your piston rings.

[shorod]

If the threads of the plug are oily, that might indicate a spark plug well seal that is leaking. If oil is leaking into the plug wells, that could very possibly be causing a misfire which would explain the rough idle and acceleration. Was there any oil on the spark plug boots as well? If so, then plan to replace the valve cover gasket with spark plug well seals as well as the spark plug wires.

You should also consider the rest of the tune items such as the air filter, fuel filter, and probably should consider cleaning the MAF sensor and throttle plate.

-Rod

[peroxwhygen]

Originally Posted by shorod

If the threads of the plug are oily, that might indicate a spark plug well seal that is leaking. If oil is leaking into the plug wells, that could very possibly be causing a misfire which would explain the rough idle and acceleration. Was there any oil on the spark plug boots as well? If so, then plan to replace the valve cover gasket with spark plug well seals as well as the spark plug wires.

You should also consider the rest of the tune items such as the air filter, fuel filter, and probably should consider cleaning the MAF sensor and throttle plate.

-Rod

Is that a big and expensive job?

[shorod]

Assuming you can find the parts it shouldn't be an expensive job, but understand that "expensive" is a relative term. It will be expensive relative to changing the air filter, but it won't be expensive relative to changing the head gasket. If you are pretty handy with tools, you could probably even do the job yourself and save some money.

I imagine your Micra is a 4-cylinder with the valve cover on top, easy to get to. From a parts standpoint, the plug wires will probably be the most expensive part. Here in the US if this is like a typical 1994 Nissan 4-cylinder, a person could probably get all the parts for the valve cover set, plug wires, air filter, fuel filter, throttle body and MAF sensor cleaners, and a bottle of fuel injector cleaner for under $200 to do the labor themselves.

-Rod