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Check Engine Light 99 Accord. HELP!

The check engine light came on a few days ago in my 99 honda accord lx. I took it to auto zone and it gave a p0420 code. “emissions below threshold message”. Talked to a mechanic and he said it was probaly just one of the sensors as the car still ran fine. This morning while driving the engine light started flashing and i could feel some shaking from the engine. Could a bad oil change, oil filter cause this problem? I think I put the wrong weight of oil in it… (10w30 instead of 5w30)

Take it back to a mechanic ASAP given the flashing CEL. Basically driving around with a flashing CEL typically means some damage to motor is likely occurring.

Oil type is irrelevant to CEL.

Thanks Andrew for the fast response. Been resarching all morning, is there anything I can try to replace myself first before taking it to the mechanic? With the recession going on money is tight and want to try to fix myself if possible.

If you don’t know what is wrong, probably not. Not only can you do more harm than good if you don’t know what you are doing, but you might be throwing parts at a problem, thereby wasting more money.

With the problems you describe, I would have the vehicle towed to a good independent mechanic and have them give it a good once over.

Check your owner’s manual, I bet if it states to use 10w30 it says 5w30 is A.O.K. as well.

Could a bad oil change, oil filter cause this problem? I think I put the wrong weight of oil in it… (10w30 instead of 5w30)

The weight difference should not cause a serious problem nor should it cause shaking.  Having the oil leak out due to a lack of properly tightening the plug or the oil filter could. 

 A flashing CEL means don't drive the car.  It could be a problem that would cause serious damage to your engine in a very sort time.  Maybe minutes. 

 Your first code and the CEL may well not be connected. 

 The old, [i]  probaly just one of the sensors as the car still ran fine. [/i] is poor advice.  First with that light on, you have no idea of a second more urgent comes up.   In any case you should be fixing the problem, not ignoring it because it [b] still runs ok. [/b]  If running OK was good enough, they would not have bothered to put a sensor on there to begin with.

I agree. “Throwing parts” at the problem will likely wind up being more expensive than having the work done by an independent mechanic. As was said, a flashing CEL means that the car has to be repaired right away, before more damage is done. Get it to your mechanic a.s.a.p.

Ok… Thanks everyone for the advice. Gonna double check the Oil filter and plug, if thats good going to have it towed to the mechanic.

Shaking sounds like an engine miss. Make sure the spark plug wires and fuel injector wires are on tight. You could have knocked something loose during the oil change.

Just to follow up, the mechanic said it was the distibuter, which 2 cylinders were miss firing. New distributer, seals and spark plugs + labor is gonna cost $540… Does this sound right to you?

Sounds reasonable to me. I guess you got ~100k+ miles out the distrib. The one in my '88 Accord lasted ~180k miles.

. Could a bad oil change, oil filter cause this problem? I think I put the wrong weight of oil in it… (10w30 instead of 5w30)

Absolutely NOT.

If the error that caused the check-engine-light is severe enough it may cause the computer to go into limp mode. This may prevent the car from running correctly. You need to get this fixed. Gas mileage and drivability will be affected.