92 VX Rpms High (1000) with Headlights

[Lovemy92vx]

Hey folks! I sure hope someone’s listening.
My VX rpms sit at 1000 when the headlights are on.
I read at one point with the VX engine, base idle should be set with the lights ON.
Is that correct or is it something else?

[Stubby79]

Is it even adjustable? Rather old fashioned if it is...

[Lovemy92vx]

OdB1. 1992, not old-fashioned. ��
Yes, the idle is adjustable.

[California98Civic]

Your normal idle warmed up will be 600 +/- 50. I have never heard of setting it with headlights on. Does not sound necessary. All that does is add load. The engine will adjust to the load. If setting it with a load were necessary, why stop with headlights? Run the radio, fan, AC, and wipers, too.

But idle does need to be set with the IACV disconnected. You have a repair manual? There is a specific procedure in the 1992-1995 Honda FSM. There is also a troubleshooting procedure involving a variety of other systems. But definitely the first step is just setting it properly.

Lemme know if you want the FSM details.

[Lovemy92vx]

Thanks! Please send the pages I need. I’d like to make sure the tech follows the manual step by step.
The mechanics I’ve used before just adjusted a hidden screw or tweaked the throttle cable nut.

[California98Civic]

On page 11-85 the manual says to first adjust idle speed as described on p. 11-102. If that does not work, they suggest six other signal checks (alternator, brake, starter, oil pressure, fast idle valve...) ... remember that it is normal for the car to be idling higher when engine is cool. That is what the IACV is for.

Here is page 11-102



Also, remember that the D15z1 engine is at normal idle at 700 +/- 50, whereas the other D15 engines are 750 +/- 50.

[Lovemy92vx]

I notice there isn’t a specific check for the headlights.
Where would you start?

[California98Civic]

Originally Posted by Lovemy92vx

I notice there isn’t a specific check for the headlights.
Where would you start?

Definitely start by simply resetting the idle strictly by the book. Lots of dudes do these things on received wisdom, which might mean your car was simply set incorrectly. For example, in the scenario you are seeing, the RPMs jump to 1000 or so when the headlights go on. They are supposed to rise under added load like that. In the right column of the page from the FSM, you can see turning headlights on is one of the test scenarios they offer AFTER adjusting idle. If it were my car, I would adjust it by the book and see if the problem goes away. If so, testing done. No parts purchased. But your guy needs an external tachometer. Don't let him do it by ear or something. That might be how the problem started.

[Stacygifford]

The eg civic tachs are notorious for not reading accurately. I have owned quite a few over the years amd myself, a long with other honda enthusiast will vouch that it is not uncommon for them to read 2-300 rpm off.

Get an external tach and follow the book, you will be good to go.

If you cant get an external tach, set it by the stock one, if at ~700 it seems noticeably high or low, adjust by ear. Too high, you waist a little gas, to low, you dont have enough oil preasure. It's better to be just a little high, but anything from 650-800 you will be just fine.
Also, it's not uncommon for the IACV to get gummed/stopped up over time. Usually just cleaning them out with carb cleaner will do the trick.

I have never heard of someone setting the ide with the headlights on though ��*♂️

[Lovemy92vx]

Thanks! That's exactly what I'll do.I'm taking her back to the shop to get my ninety dollars worth in the morning.
To be clear, I haven't had the idle set with the headlights on. After more research, I think what I read was that the headlights are the biggest draw on power. And that That was peculiar to the VX.
I've never seen a car go from a 650-700 idle to 1000 and stay there until I turn the lights back off. It does fine with other loads, even AC.
I just brought this car from Denver to sea level. It got in the mid 40's all the way back to California. Now I'm getting low-mid forties where I expect mid forties to low fifties.
I really do drive Pearl like Wilma sans Fred, diligently hypermiling. Highest speed 50-65, mostly flat, some short trips cold.
So my economy is down, and my idle is up. I Really like to drive with my lights on for safety.
I will keep posting the results.