Problem: RPM Fluctuating

[Kianbeng]

I'm driving a 10 month old 323. Recently noticed that my RPM kept on fluctuating when I'm stationary (stopping at traffic lights). But it's not always happening....but it seems pretty obvious recently. Although RPM is fluctuating from 500rpm to 700rpm, sometimes I can feel as if the car is almost "dying", then suddenly, it'll rev higher to compensate for it.....

Mileage wise, I've clocked about 24K liao. Done 4 times of oil change liao. Recently changed to Shell Helix Ultra (stock was Shell Helix Super). Engine noise was noticeably quieter during cold start after this synthetic oil change. But I've yet to change any spark plugs or air filter.

 

I'm thinking of resolving this problem myself first before approaching MM. Coz if not.....if they find out it's a small problem (ie wear and tear stuff), they'll charge me exorbitant fees to replace them coz it's not under warranty for wear and tear parts.

 

Any suggestion? Anyone having this problem also?

 

Think, in the meantime, I'll try to change the spark plugs and air filter. Hopefully it'll help.

[Pauly75ts]

RPM kept on fluctuating when I'm stationary

 

Hi! there, KianBeng,

 

Sounds like you've got a dirty idle valve. I've yet to take a look at the 323 engine, even though my bro-in-law's got one.

 

Do you drive around where the roads are dusty & dirty? You might have to clean the induction assembly too. Firstly, check your air filter, if it's dirty, then the rest of the induction assy will be too, i.e. AFM, induction hoses, throttle valve, idle valve.

 

You can use carb cleaner to spray into it, then wipe it clean, pay attention to the AFM sensor, it's very fragile, use cotton bud and lightly wipe.

 

Check your spark plugs, it should be light brown in colour, are there bits of dirt on it.

 

Rgds

 

Paul Yong

[Kianbeng]

can use the carburettor spray for fuel injected engines meh? hmm.......

 

think I'll just clean up the air intake pipes with a wet cloth and also change the air filter asap. Will also buy the sparkies for it.

 

just wondering could it be the ECU that needs some adjusting? coz....I feel that the engine was just trying to settle for idle at 500rpm. But when it drops to 500rpm, it realises that it's too low and it will rev up a little to compensate.....then falls back to 500rpm again.......

 

Another thing was that.....I realise that it happens only occasionally. Not everytime when I stop at traffic lights. Maybe.....say half of the time?

[Wymun]

Before doing anything drastic, like taking apart your whole throttle body to clean (though that is still recommended), you may wish to check if it happens only when the air-con cuts in (and radiator fan starts turning)??

 

I have a similar problem, but only when stepping on the brake (stationary) at "D". Also, mine's a Sunny B14 (A). Noticed that when air-con is momentarily off, the rpm sits at 600-700 rpm. But when fan starts-up (air-con cuts in), it dips to 500rpm or so and the car receives a momentary loss of power (i.e. lights dim a bit - if at night) and it seems as if it nearly stalls. Then it goes back to normal, but still sits precariously at about 600rpm or so.

 

If that's the case, I think it's okay, cos it shows that the system is working and starts compensating for the power loss suddenly, which is normal when the air-con kicks in?? But you may wish to see if they are any air-way blockages in your throttle body too as a safety measure...

 

I guess a solution could be adjusting to a higher idle rpm (using adjustment screw if available). But for me, my idle RPM was okay at 800rpm at "N", so that didn't help... In my case, I'm okay with it thus far cos the car hasn't stalled yet....Unless someone can offer a better solution...

 

Also, check that your hoses are not leaking (esp vacuum hose).

Edited December 15, 2002 by Wymun

[Civic9922]

I have the similar problems also on my 92' civic. Thought because it is an old car so

have to bear with this problem. I have this problem for months liao.. had changed plugs, cables, clean air filters, change idle sensor, tune up the idling, even service the injectors.. but they will come back.

Like Wymun had mention, I guess it must be the air hose somewhere..

For my case, it usually happen in the morning. After some hard acceleration, it can go away. Rainly days and night don't happen also. There are times I notice after restarts the engine, the fluctuation is gone. Mmmm????

 

Really need some kind soul out there to give advise to this problem.

[Kianbeng]

mine's fluctuate regardless of the aircon. But when aircon kicks in, the RPM immediately shoots up to 800.

 

I noticed that most of the time, there is a very slight fluctuation. almost harmless. Just that when it fluctuates more, then I can feel the car almost stalling when it dips.

 

Mine's a manual. When I stopped at traffic lights, I only pull my parking brake. Nothing else.

 

Infact, I would prefer a lower RPM though coz it'll save me more fuel. BTW, I've checked the vaccum hoses. They are alright physically.

 

Actually, now I'm less inclined to think that it's something to do with mechanical parts. Why? Coz with full tank (55L), I can travel to 670km. So, now my guess is probably the ECU or the air/fuel ratio. It could be that my air fuel ratio is too lean now. (too much air? not so good also, coz may cause pinging.)

 

hmm.....guess I should send it for a exhaust gas check to really find out.

[Mlksh]

When this happened, did you try to off the air con? If you try to off your a/c and problem gone, it i due to the air con sensor. i got this problem too and have a check in the workshop and mechanic found out that is the air con sensor Change it and cost only $25. He really an expert, once look and he know. Go to the air con shop and get the mechanic to bypass the sensor and see if the prolem is similiar and if so, get it change.

[Mlksh]

Is not normal to be at 500rpm when air kick it. mine got the same problem too and is the a/c sensor faulty. get it change and only cost $25 or buy at spare part shop and diy.

[Mlksh]

Check the a/c sensor. I got this problem. Change the sensor not ok liao. Only cost $25 and dun need to bear with the problem. Any air con shop can do. To test, bypass the sensor by taking off the connector and see if problem come, if so, get it change.

[Kianbeng]

I've tried. It's independent of the aircon.

 

Basically, after running in for a few months, the problem went away by itself. I attribute this maybe to the ECU slowly adjusting itself? Or maybe because after some servicing, I replaced a 'not-so-good' plug.

 

[Yeobh]

RPM fluctuation at idle speed is mainly due to the poor power balance between cylinders- that is one or more of the cylinder spark plugs are not firing at the max permissible kilovolts.

The cause can be due to wrong spark plug gap setting, poor connection of high tension cables, high resistance of high tension cable ( usually cause by the mechanics pulling the cables when replacing spark plugs indirectly causing internal damage to the carbon conductor) and high compression cause by carbon built-up.

The next time your mechanics replace the spark plugs, observe how he pulls the cables. To over come this problem, suggest to your mechanics to use a spark plug cable puller

[Civic92]

Thanks pal for your kind reply, Mmm, Aircon Sensor,

where are they place? (Civic ESI)they look like?

squarish with the plug-in pins below?

 

Thanks..