Hello. I have honda civic 2005 Lx with 170,000 miles. I noticed increased RPM about 1.5 with cold start but no missfire. I attempted to take out ignition coils to see if genuine ones solve the issue. It is very little rainy today with high humidity. After I put new ignition coils, I noticed increased shaking with misfire. I have not touched anything except for putting in/out coils. I ensured the position and connection of the coils. Is this anything with humidity? I did it really quick without much exposure to the rain. Do you have any idea how to resolve this issue? at least return to previous condition? Thank you in advance!
Put dielectric grease in the plug end of the coil. Make sure you hear the click when seating the coils on the plugs.
I’m a little confused
“I attempted to take out ignition coils to see if genuine ones solve the issue”
Does that mean you had aftermarket coils in there?
If so, why?
Are you still using the original plugs with 170,000 miles? If so, you’re way overdue
Many cars have an elevated idle for a few seconds, during a cold start. This is normal in many situations
Did you put dielectric grease on the boots?
I’m not sure if this is the case here, but on some cars, the coils and plugs are not interchangeable from cylinder to cylinder
@knfenimore Thank you for your recommendation. I’ll try dielectric grease and put them in again. @db4690 I purchased OEM ignition coils but as it turned out my fuel injectors were bad and misfire stopped after replacing injectors. I tried to put back old genuine coils to see if it solves elevated RPM. I’ll but the dielectric grease and see if it works! Thank you
The dielectric grease is to keep the spark from arching during damp weather. Glad the injectors helped your problem. Run a bottle of Techron through the engine at every oil change and it will keep the injectors clean.
Are the part numbers on the new coils identical to the numbers on the old coils?
Again . . . are you still using the old plugs with 170000 miles . . . ?
What exactly was the problem with the injectors?
Electrical open circuit or short circuit?
If they were plugged, did anybody try cleaning them first? The most effective method is to connect the fuel cleaner directly to the fuel rail and actually run the engine on that stuff until it stalls
One more question . . . does the elevated idle disappear after the engine warms up?
@knfenimore Thank you again for your help. I just re-tried to put the coils all the way in with decent pressure and misfire disappeared.I’m getting dielectric grease to improve performance. Thank you again. @db4690 the injectors had never been replaced until 170,000. Now I have replaced all 4 spark plugs, ignition coils, and injectors. I found a local mechanic who would replace them with $60 labor. I bought 4 GB manufactured injectors(around $250) and misfire resolved even though RPM was still high with cold start, which is tolerable. Thank you for your help!
Thanks for the reply
And congratulations on resolving the problems!