Help: Oil effecting idle?

[zyrix]

I have a 1996 Honda Civic Lx 4dr, and for the past few months i have been having a problem with what seems to be the idle, when i'm sitting at a stop light or whatever with my A/C on the car seems to idle too low because it idle is really rough/vibrates harshly when the fan for the ac kicks on. It is also an intermittent problem because some times it can be absolutly fine. A frined of mine told me that it could be because there was 'crap' in my gastank and it was clogging up my gass filter, so i wen't and changed that, but it hasen't stopped, the only thing that i did differently just before it started happening was i changed my oil, i started using valvoline synthetic (10w30) as apposed to castrol 10w30 i think. Could it be the kind of oil i'm using? or is it somthing w/ the fuel system? Any idea?

 

[T-Keith]

I don't an oil change is going to do that, unless it's a drastic change in viscosity. There are an endless number of things that could cause it. Check the basics: engine codes, air filter, spark plugs, ect.

-T

 

[olddognewtrks]

Have a mechanic who knows Hondas (not me, I know a little bit about Mazdas) check out your throttle body. There are one or more very small air flow passages in the throttle butterfly area that can get gunked up over time. These are enabled by switches or circuits tied in to the A/C function. When the A/C kicks on this doesn't allow proper extra air (and fuel flow) to compensate for the A/C load even if all the switches/circuits do their job. Result; idle speed drags down and it shakes and/or dies. Second thing to check is various switches/circuits that enable that extra air/fuel flow.

 

[moribundman]

Not sure what parts the Honda engine has, but look for vacuum leaks, a bad MAF or MAP sensor, a dirty or defective idle control valve, a dirty throttle body, bad spark plug wires and/or plugs. Start with the cheapest thing... It could well be a combination of issues -- I know, on my car it usually is.

[ February 19, 2004, 06:40 PM: Message edited by: moribundman ]

 

[ZR2RANDO]

I'd say think about the work that was done just before the problem started..maybe a vacuum line was loosened, maybe a wire? Check that kind of thing

 

[heyjay]

On my 1992 Honda Prelude SR with DOHC motor and variable intake manifold, the IAC (Idle Air Control) motor was mounted separatly from the Throttle Body.

A good distance away actually, near the center of the intake manifold plenum.

Mine would idle VERY rough unless at least once a year I took off the IAC module and cleaned out all the passages.

Especially there was a little screen, looked like for backfire protection, that would cake up.

I used 3M Throttle Body Cleaner to clean all this and it idled like new.

Jerry

 

[mf150]

just to state the obvious, putting the A/C on will cause, in itself, a noticable rpm drop.

 

[javacontour]

You may check to see if the compressor bracket it loose. I had a similar issue, rough idle with A/C on. It was the compressor vibrating.

Just another, less obvious possibility.

TB

 

[Patman]

Since this is more of a mechanical issue, I'll move it to that section.