I have been having a slight problem with my idle. Recently I did get into a small car accident but ever since right before that my car has had a small idle problem. Check engine light went on and I had problems starting my car. Anyway I did the usually fluid changes and Map sensor replacement. I also had all the recalls done. My question is, can it be maybe a clogged fuel filter, leaking head gasket, VAFC involvement, O2 sensors, that is causing my car in the mornings to lose idle? And when I say loose idle I mean I go through first and second gear ok then in third I am cruising then its like a sudden loss of like 500rpm and you can feel it even when I am pressing on the gas. Sometimes at stop signs my RPMs go way down to like 2 bars and once it shut down. Other than that the car runs fine. My check engine light keeps going on as well and when it was checked out at the shop that repairs the car it keeps coming up as a resonator/charcoal sensor error or something like that. Its always stayed the same but that has been completely replaced and triple checked. So I called up the dealer and am taking it in on Thursday so they can trouble shoot. Any ideas? Anybody?
Thanks

 

How many miles are on your car? Have your valves ever been adjusted (by a trustworthy / competent mechanic)? Are you using the partial throttle portion of the V-AFC to do any fuel tuning? What are your throttle position settings for partial / full throttle (ie. 10% / 50%)? Have you tried resetting the ECU by pulling the ECU backup fuse (#25)?

Unequal valve clearances can cause a rough idle, even if they are all "within spec". Taking it to the dealer for this service is usually a waste of time and money, since they will just make sure they are "within spec". The Honda specs for minimum / maximum valve clearance are too large IMO. I am amazed at how smooth the idle can be if all the valves are set exactly to the same clearance (ie. .008" Intake / .010" Exhaust).

The OBDII ECUs will behave badly if you use the partial throttle MAP correction features of the V-AFC. Since the ECU operates in closed loop during partial throttle, it will learn to tune out any partial throttle fuel corrections that the V-AFC makes. This will cause all kinds of strange behaviors (stalling, hesitation, etc.). For the same reason, the throttle "switch" of the V-AFC needs to be set high enough that the V-AFC will ONLY apply the fuel corrections when the ECU is in open loop mode (high throttle, high RPMs).

I have no idea why you would be getting that particular OBDII diag code.

 

i only get the drop of rpms on really hot days down here at like a stop light or something but its only if i rev it up it will come down like normal and then just drop to like 2 bars and raise again

 

Sounds normal to me, especially if the engine is heat soaked. The EACV (electronic air control valve) is probably not fast enough to compensate for a quick throttle closure in neutral.

 

I have 40000 miles on the car. Yes it does get very hot and very humid here. So that may be the reason... Thanks Gernby