Problem with unstable rpm while moving

Hello,

I have seen this happen when the throttle actuator is dirty causing the sensor and the acautor to lose their correlation. Here is a guide that will help you see how to fix the problem, disconnect the battery before you begin.

https://www.2carpros.com/articles/throttle-actuator-service

Please run down this guide and report back.

Thanks for this post I had this problem and the service fixed it. I love this site.

My car's RPM has started fluctuating ever since i got the throttle body serviced. The rpm rose beyond 1000,after the service.I noticed it and the next day i asked my mechanic to fix it,because earlier on it was perfectly stable and the car was giving good mileage too.He very reluctantly slowed it down by turning a screw with an allen key on the throttle body,where the throttle plate rests. With that,for the time being the RPM came down to normal but started fluctuating when the air-conditioner was turned on. When the radiator fan starts automatically,the RPM drops slightly as if the engine was about to stall,but then gains and comes back to normal. This is felt more when you are driving in town and in traffic where u have to stop at traffic lights etc.Hardly felt on a long drive or highway. A Honda pitstop mechanic,whom i went to lately, reset the entire thing,using a computer but my car is still not the same.Pls advise!!!

the cleaners today take a coating off the throttle bodies and tend to cause this kind of issue. you are not to have them cleaned as per the manufacturer. most likely the throttle body has to be replaced.

Roy

Thank u very much Roy.I will start looking for it cos i doubt if the spare part dealers keep brand new throttle bodies cos anyone hardly changes them.However i will check the market.Thanks again.

my friend and I just replaced the cylinder head in my 1987 honda civic and took it out for a short test drive (5 mi). On our return trip, the car suddenly was hard to control, but we made it back safe (whew). When I parked the rpm's were at 4000 (!), same when in neutral. Gas pedal seems normal. We think we probably knocked something out of place in the carburetor when installing the head - any thoughts?

I'm not familiar with a Honda City. Typo?

Sounds like a possible vacuum leak. Go over your work and look for anything not reconnected or rotted rubber and leaking.

Don't run it too long, but listen for a hissing sound as the engine idles.

it idles at 4000 rpm -so I can't hear anything (!) but the engine... had no idea a vacuum leak could do this, hmmm... I guess we'll have to check all the carburetor lines...

IF there is a brake booster hose on that one, that is what I would first check just due to the size of the hose. More air, the higher the idle. In a sense the carb or throttle body is one large adjustable vaucuum leak.

Hi,

My car is 2004 Automatic,Made in Thailand imported in UAE . Recently my car started giving jerks when running at slow speed (between 20KM-60KM) . I did not notice the jerks at higher speed. One local mechanic asked me to put Injector cleaning oil in in the fuel tank and after that it worked fine until the next oil change. It started giving the same jerks when i filled the patrol tank. Again I put the same oil in the Patrol tank but this time the jerks not vanished.

I have changed the engine spark plugs and now my mechanic is suggesting the spark plugs coils to be changed for testing.

I'm feeling the jerks and whenever the car stops at red signal I have to either switch off the Air Conditioner or give much acceleration . The RPM needle is not stable also it goes to 2000 RPM and then with jerk it comes to 1500 and then suddenly it change. It is not stable.

The new coils costs too much and he is not sure also that installing new coils will fix the problem or not.

The honda service station is quoting 140$ for diagnosing the problem. Please help me .

With Regards
Yatin

Is the Malfunction Indicator Light showing and have you checekd for trouble codes?

Hello KHLow2008 ,

The engine check light (Malfunction) is not turned on so I did not get it checked from computer . I drove to high way and i felt the same jerks at the speed of 75 miles also. One of the local mechanic suggested me to change the spark plug coils. Kindly suggest.

Regards
Yatin

Symptoms do indicate possibility of the ignition coils as the engine seems to be misfiring.

Have the coils tested. Usually only one or two is defective and not necessary to replace all.

Hi Yatin,

You got any solution for this? I am facing the same problem with my honda city 2008 model.

Naveed

Any update on this?

When I'm driving my car, often it operates smoothly and no issues, but on occasions, I do experience a problem, that the RPM increases, even when I'm braking or change gears, the RPM increases, and the engine revs up. The acceleration also increases, but it's under control, not very dangerous. However it's irritating and it's a problem I can't quite figure out as to why this is happening.

try cleaning throttle plate on both sides an diac hole with choke cleaner.

when I start engine rpm comes down on o and car switch off.

Have the idliong speed readjusted to see if it works.
Get the throttle body and IAC cleaned as well.

I had an engine overhaul. Since then, the RPM does not stay stable and keeps fluctuating up and down when in drive. The acceleration has also significantly decreased and seems that the car is choking. Had a computerized check up and it suggested high air input. Have tried replacing sensors but that has not helped either. Sometimes the engine starts missing all of a sudden so even tried replacing the distributor but without much luck. Had the plugs replaced with new ones too.seriously running out of options guys. Please help !!!!

Check the valve clearances.
What are the trouble codes you are getting?

My car have RPM problem when I start in a morning, its RPM going up till 4 x100 and after half an hour its going down automatically.

I have check many mechanic but problem are still not solve.

your swift response will be highly appreciated.

regards
YS

Check the idle air control valve and clean the throttle body

Is the MIL indicating?

No... its not indicate.. Just RPM going up for 30mins in a morning.

Follow Rasmataz's recommendation, check the IAC for sticking.

Ensure you have sufficient coolant in system and coolant hoses to IAC are not clogged.

Check for vacuum leakages.

After engine warms up to operating conditions, what is the idling speed?

IAC is jammed, if I trying to open hardly so it will break and here in Karachi, Pakistan new IAC are not available in open market.

After engine warm-up the car running normally with idling only when I start in morning or after 2 or 3 hour time its idling and RPM goes 4x1000 for half an hour or more.

If you have removed the IAC from the housing, don't disassemble it.
Spray some rust penetrant into the [ports and let it soak for a while. Use a feeler and gently pry at the vale to make it open. DO NOT force as it will damage the valve. Try to slowly work the valve loose. It might take some time.

Use carb cleaner to clean what ever dirt inside the chamber and after job is done, make sure the valve moves easily with minimal force and befor installation back to throttle body, spray some rust penetrant into the chamber again to lubricate the bearings. Let it soak for a while as the 2 bearings would seize if it is not lubricated.

Hi, i was wondering if you could give me some advice on my new Honda City. When i am just sitting at the lights (in 1st gear or neutral), just idlying, my car seems to be "jittery". Basically you can feel it shaking intermittently, like its gonna stall or as if its revs are too low. I took it back to my Honda dealer's service centre twice, and both times they checked the computer and said that there is no problem? I find it soooo frustrating, it feels like im driving an old car :-( Do you have any ideas what this may be and if its normal?? Thanks.

No vehicle new or old should have such problems.

Note if occurrence is when A/C compressor cuts in or out.
This could be an idling or electrical problem and the computer is not going to show anything.