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Spark Plug Problem

by Silver Bullet December 14, 2005



I just replaced my stock spark plugs today with NGK iridium IX. The Rolla is an '01 LE with @ 110,000 miles.

The problem is the idle is rough and the CEL came on and is staying on. I haven't had a chance to pull the code yet but I will post my findings tommorow.

Thanks in advance for any input.

Did you notice a difference in performance with the NGK Iridium IX? Better gas mileage, better acceleration, peppiness? Any noticeable difference from the stock plugs?

Well since the 01 came with iridium plugs stock, the drivability seemed the same. The difference with the NGK IX is the idle is irratic as if the engine is misfiring. I have only driven the car about 25 miles since I changed the plugs. Fortunately, I still have the old plugs so I'll probably reinstall them to see if there are any changes.

Should not have caused a problem with the idle - unless the plug reach, plug gap, and plug temp range are off. I'd make sure that the coil on plug modules are on tight - might have to look at the boot end and see if there is any corrosion in there. Dielectric grease might help (basically silicone grease - helps keep moisture out of there to prevent corrosion.

Did you add any anti-seize compound to the plug threads? Used to be common fair with some older engines - but I've seen many newer engines being very sensitve to the coumpound. The plug reach is far enough that any extra anti-seize compund that gets worked in there will cause engien misfires and detonation.

Let us know what the turn out was.

I have an update. The code scanner found 4 faults- 2 P0300 Cylinder Misfire Detected and 2 P0301 Cylinder 1 Misfire Detected. I pulled out the cylinder 1 spark plug and found the gap to be 0.035" not the FSM spec 0.040-0.043" for new plugs. I carefully increased the gap to 0.044" and reinstalled the cylinder 1 plug. After start-up the idle was smooth like normal and after 50 miles of driving everything is still normal with no CEL.

Cool deal. Might want to double check the gaps with the others, just for completeness. Kind of weird that the plug got so out of spec - my Densos and NGK replacements had protective cardboard sleeves to protect the threads and preserve the gap.

Very interesting result that you have there. That a sparkplug closed 5-10 thousandths of an inch too tight would cause that kind of problem. We're talking around the thickness of two or three sheets of notebook paper max.

Should I replace my plugs in the 2005 Corolls S? I don't see anything in the owner's manual in reference to spark plugs. I would probably use OEM.

Max

Nothing in your manual? Bizarre. Didn't you get the "Passport to Performance" maintenance guide, either? Plugs get changed at 120,000 miles. There's a whole other thread about this going right now. Try the search function. It's a great way to get quick answers.

Bikeman982

I have an update. The code scanner found 4 faults- 2 P0300 Cylinder Misfire Detected and 2 P0301 Cylinder 1 Misfire Detected. I pulled out the cylinder 1 spark plug and found the gap to be 0.035" not the FSM spec 0.040-0.043" for new plugs. I carefully increased the gap to 0.044" and reinstalled the cylinder 1 plug. After start-up the idle was smooth like normal and after 50 miles of driving everything is still normal with no CEL.
Hard to believe that such a small amount of gap difference couls make it misfire and give you a CEL.

 

Great to hear that it is running better.



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