92 VX Rpms High (1000) with Headlights
 

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?

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

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

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.

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.

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

https://ecomodder.com/forum/attachme...1&d=1532356063

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

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.

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 ��*♂️

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. :snail: 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.

Ok, now I really appreciate you folks. Today was a cool, humid day. I go for a ride before I take her in. I flip the lights on and the idle was Fine. Reeeally?
(ive wondered if the ambient temperature affects the non metal parts in the system make it react differently. I Want that to be a clue. Is it?)
In fact, it was "a bit too low". I sat in the passenger seat while the mechanic watched the idle adjust to the changing loads. It idles "just right" with the AC on high! It shuddered with the headlights On and did Not adjust back up when they were turned off. Confound it.
This poor fellow believed me about 1000rpmsheadlightson. He saw it do it one time thank goodness. And I have video.
He kept repeating the previous adjustment was basically disconnecting the battery and letting the ECU re-learn ($90). I had to say that That was when it went haywire. I had to insist repeatedly that he use an external tach and follow the shop manual procedure. When he disrespected the book with a slight twist of the head, I persisted: "Please! Can we just start from the beginning?"
Going back in the morning. I'm going to read the steps to him and we'll walk through it together.

Excellent. Test don't guess. Follow procedure. Method is better than random! :)

Random idea: could your battery be failing and really be generating a high load on the system?

Not so random at all! The guy today said the battery cable was totally loose. He was surprised it started. I had noticed it almost didn’t need to turn over to start.
All this said, I still wonder about the ambient temperature and how it would play into this system. Cool weather is affecting something....
Tomorrow we’ll fill up and hit the road!
I Still want to learn the step by step.
I have a slightly underperforming HX to do too.
By the way, I bought a magnet for Pearl’s back end. It’s a yellow yield sign “banana slug crossing”. I think it’s fitting considering the whopping 96 horse power. ::-)

To be specific about what the mechanic did today—discovered the battery cable was untightened, cleaned it replaced, then let the engine run until the ECU re-set itself. They were going to charge me for another hour to finish their previous work properly, agreed to cut the fee in half which I accepted at the time. I guess they’re not my mechanics anymore. Tomorrow I’ll get my money back.

I am not sure, but I am pretty confident an ECU cannot be reset by running it a few minutes. If the battery cable being loose was causing your problem then tightening down the battery cable properly would solve the problem virtually immediately. So I don't think this is going to solve the idling irregularities you're talking about. They don't sound like great mechanics. And they still haven't reset the idle?

Nope. And they aren't interested in my business anymore. My expectations were too high. Why is it offensive to ask that a specific procedure be done? I should learn to do it myself like he said (!!!!!) At least I'll get my $155 back to leave them alone.
In the meantime, the idle with the headlights ON appears perfect on the gauge and drops down so the steering wheel vibrates a little.

This is not a super-hard adjustment. Good basic project for learning. You can totally kearn to do it better than they were doing it.

Thanks! I'm going to drive it the next two weeks and hope my mpgs improve. I'll report back. If they don't I'll go for it!
Then I'm off to Utah where I finally found a white '94 VX! It runs normally on video and is still I'm told delivering the high mpgs. The compression tests showed basically 150 dry and 180 wet. I hope that's a decent number for another 250k plus engine. It was on car gurus.
I guess that's another thread!