hello,

i have an issue with a surging engine. this happens when the car is warmed with an electrical load and only when stopped.

after much searching i believe i narrowed it down to the following problem: low voltage.

with the car off i get a reading of 12.5 (est.) volts from the battery.

upon starting the car, i get a reading of 14.4 (actual) and the idle is fine.

once the car is warmed, if i turn on my stereo, the voltage drops to 13.1 (actual) and remains there regardless if the stereo remains on. if i rev the motor, the voltage remains at 13.1.

after about 5 minutes the voltage dropped to 13.

i feel that this may be causing bad readings either to or from the computer (hondata s300) and therefor causing the idle issues.

i have recently cleaned all the grounding connections (three cables total) but this solved nothing.

perhaps these two issues are unrelated. understand, this thread is meant to be about the voltage issue first.

thanks for your help everyone!

 

Test the alternator & battery. It sounds like you have an issue with one...
You should be seeing around 13.8-14.2 volts while driving.

If you are running a smaller under driven crank pulley, get rid of it and use an oem sized one.

 

i am under the hood with the car warmed up and i hit the throttle. the voltage stays at a constant 13.1. am i meant to see a spike or should the voltage be 14.4?

i have recently changed the crank pulley from a an OEM three-position to an OEM single position. same size, just lighter weight.

 

The alternator has a lo and hi output mode...12.5-13 volts is normal operation when that adding charging isnt needed.

If this is running a stock ECU and stock injectors, the surging is more likely a bad IACV or a vacuum leak near the intake manifold

 

i have a Civic CX with a B18C. Stock injectors, CX fuel pump (which i recently read may be an issue) and a Hondata S300.

I have recently changed the IACV as it was bad and just noticed the PCV valve is also bad. I did the "brake cleaner spray test" around all the vacuum lines and seals and am confident there isn't a leak.

 

Check if you have a Fast Idle Thermo Valve (google FITV rebuild)....

 

i don't have one. i am post '95. i wish i did because i'd have had that thing done last week. i'm thinking spark plugs/dizzy cap, bad o2 sensor (narrow band as of now) or bad map sensor. these are all things i haven't checked yet but have recently read could all be problems. i believe some of these could be more related to poor idle rather than my situation, surging idle.

please keep the suggestions coming.

 

Spark plugs/dizzy cap generally don't cause idle surging...

Can you elaborate on what you exactly mean by surging idle?
The idle is bouncing from 500-1000? etc?

 

that is exactly what i mean by surging. loping?

i spent some time under the hood tonight and found three loose bolts on the intake manifold. two were under the first and second runner. those weren't easy to get to.

upon starting i found the motor kicked over a lot faster. it usually takes three turns of the starter (not to be confused with three turns of the key). it started on the first turn. perhaps because i was playing with the throttle a bit about half an hour before.

i took it for a short drive to warm up the motor and found that the surging was still present.

i should mention that i have been playing with the cooling system as of late. i replaced the rad and hoses. with all the work searching out this idle problem, i have been adding lost coolant as needed due to removing the IACV so many times. tonight i found the overflow reservoir empty so i filled it before my little drive.

is it possible my loping issues could now be caused by air in the coolant hoses/lines? i also need a new PCV valve. mine is sticky and doesn't rattle. maybe this is part of the problem? i don't think so either.

i'm still going to check the dizzy and rotor, plugs and gaps. i'm sure replacing these will REALLY help my issues.