Engine occassionally has slight tremor when idling.

[seraphn]

I have a 1999 Maxima thats getting close to 110,000 miles on it. My engine has been giving me a slight tremor when idling and occasionally when accelerating.

recently, I've had the spark plugs replaced, which seems to have fixed the bumpy acceleration, the the tremor is still there. I've taken it in to the deal to get it looked at and was told that the ignition coils needed to be replaced due to the new sparkplugs damaging them. I tend to take what the dealer says with a grain of salt, so does this sound credible? any opinions would be great!

[MinisterofDOOM]

Bad coils could certainly cause a rough idle. I don't see how the spark plugs could cause damage to them, though. And if it's just a rough idle, it's not likely that more than one or two coils are bad.

What brand plugs did you have put in?

[seraphn]

thanks for the response. I took it to the dealer, but I didn't ask what kind of plugs. The guy told me that because the coils were old, the new plugs could have damaged them with the stronger spark. sounded like he was bsing me, but I wasn't sure. what effect does a bad coil have?

[MinisterofDOOM]

The coils are what provide the power to the spark plug so they can produce a spark. If they're bad, they'll be weak or will not function, resulting in poor combustion in that cylinder which is what causes the tremor.

If the dealer replaced your plugs, you should be fine. I asked because a lot of people who use non-NGK brand plugs (the factory plugs for the car) sometimes see slightly rough idles as a result. The dealer would only use the correct NGKs.

[NutriaforBreakfast]

You can check to see if your coils are bad by using a multimeter(resistance check) and make sure the wires are sending DCpower (voltage check). You might try cleaning your throttlebody and idle air control valve too. My 95 was acting like yoursand until I cleaned the IACV it wouldnt run right with new plugs.Also, the IACV passed the multimeter test but there was somuch carbon it wasn't really working right. Try these things beforespending money.

[seraphn]

Thanks a lot for all the help. I will try to do some of that maintenance myself as suggested.