2000 Honda Accord engine RPM fluctuation

Tiny
IAMFURQAN
  • MEMBER
  • 2000 HONDA ACCORD
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 145,000 MILES
I parked my car and went on vocation every thing was fine until then after 20 days when I came back and started my car it was running ok on idle. But as soon as I accelerated RPM started fluctuating. When I kept pressed accelerator car does't accelerated. When I pressed accelerator hard it moves with jurk and then after some time even I kept accelerator pressed RPM started coming down. I drived for 20Km it kept on doing same. I brought it to mech he replaced fuel pump, nothing changed, then he changed fuel regulator no change. When he manually turn fuel regulator off, car acceleration becomes ok. The moment he turn regulator on again every thing was same again. He had also cleaned fuel injectors. Engine scan did not revieled any code. I have given ECU reset by disengageing battery connector for half an hour and then connecting it back after five minutes when I started it every thing was ok. After driving almost 20 to 25 Km now again it has started same RPM fluctuations.
Monday, June 30th, 2008 AT 12:28 PM

26 Replies

Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
Hi iamfurqan,

A lot of things can jam up when not used over a period of time. There are 2 things likely to cause this problem.

1. Throttle position sensor. Check the TPS voltage at fully closed (0.5v) and open (4.5 v) throttle and confirm voltage increases smoothly with acceleration. Some slight difference in reading is acceptable.

2. The IAC valve is stuck.

Is the idling speed normal? Cold start more than 1500 rpm and lowers to 700 when engine operating temp is attained?
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Tuesday, July 1st, 2008 AT 9:01 AM
Tiny
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Thx for the reply.I
yes idle RPM ok. If I left car running on idle it kept on running as long as not being switched off. And normal idle RPM are 700. Kindly would you tell me what is IAC valve.
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Tuesday, July 1st, 2008 AT 9:12 AM
Tiny
KHLOW2008
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Hi iamfurqan,

Intake Air Control valve. It is the unit attached to the lower part of the throttle body with 2 coolant hoses passing through it.

Idle rpm = 700, what about with A/C on and also when engine is cold?
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Tuesday, July 1st, 2008 AT 10:27 AM
Tiny
IAMFURQAN
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Hi khlow;
thanks for reply. Idle RPM are 700 and when puting on AC. It droped around 550-600. But still it kept runing.
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Friday, July 4th, 2008 AT 11:55 AM
Tiny
KHLOW2008
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Hi iamfurqan,

Idle rpm should not drop when AC is operated so the IAC is at fault. You need to clean it and the throttle body.
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Saturday, July 5th, 2008 AT 6:14 AM
Tiny
IAMFURQAN
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Hi sir,
i had checked my car from honda and they also revieled the same thing you had mentioned. They are asking to replace IAC valve and throttle body.
Kindly can you tell me it is whole throttle body need to be changed or it is throttle position sensor which
actualy have to be changed.
Does idle control valve or intack control valve is same thing.
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Sunday, July 13th, 2008 AT 5:37 AM
Tiny
KHLOW2008
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Hi iamfurqan,

The throttle body comes as a whole unit with the IAC and throttle body. It is not going to be cheap.

If the check engine light is not showing, I would recommend cleaning the IAC.

Get yourself a can of carb cleaner. Remove the intake hose and spray into all the holes you have inside the throttle body. Wait a while and start engine, spray again if it is very dirty. Remember to push the throttle valve open to get to the inside. Engine would stall if you spray too much, it is ok, just try to rev up a bit to keep it going.

Get a second opinion, might save you some $.
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Sunday, July 13th, 2008 AT 7:53 AM
Tiny
IAMFURQAN
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I have replaced my throttle body and IAC valve. My car was running very smooth for few days almost 100Km. Then one morning when I started my car it started with RPM at 2000 after 3 or 4 minutes it started fluctuating RPM between 2000 to 3000RPM. Moment I put my car in drive things become ok. After couple of days now again its the same as arlear. It is running ok at idle but when I put it in drive there is fluctuation in RPM. There is too much fluctuation. When I am driving sudenly RPM start falling then again goes up like I am driving at 100Km speed it start droping to 60Km then sudenly it will start increasing to 100 speed. Couple of times it stall at red lights and it is giving very jurking start when I accelerate from stop. Pl tell me now what to do.
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Friday, August 22nd, 2008 AT 4:17 AM
Tiny
KHLOW2008
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Hi iamfurqan,

Check the radiator coolant level and see if coolant hoses to IAC are clogged.
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Friday, August 22nd, 2008 AT 10:26 AM
Tiny
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I have checked radiator coolent level, it is ok and also IAC hoses are not cloged. My mechanic is insisting to replace IAC again since it was running ok for first few days after replacement.
I checked my old throttle body with multimeter there was smooth variation from 0.8 to 4.6 kohm and there was no continuity at IAC. Is it means that my throttle body was ok only IAC was bad.
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Saturday, August 23rd, 2008 AT 1:01 AM
Tiny
KHLOW2008
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Yes, TPS is ok, IAC is bad if there is no continuity.

It is possible for the replacement IAC to be bad, was it a used or new unit thet you replace?
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Saturday, August 23rd, 2008 AT 6:39 AM
Tiny
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Yes that replaced IAC was used. Later in the day I had checked voltages at IAC, MAF sensor and TPS all were ok giving battery voltages. Finally I had replaced thermostate and since then every thing is ok I have driven 20Km and through out running it was perfactly smooth.
Keep in mind the thermostat I have replaced is now UAE gulf spacificationi earlleir thermostat was amarican spacification since my car is imported from USA. What do you think that might have been the problem. Temprature here is most of the time very hot.
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Saturday, August 23rd, 2008 AT 12:29 PM
Tiny
KHLOW2008
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Yes, the thermostat can cause the surging if the rating is different.

That was the reason I reminded you to check the coolant level and hoses for clogging.
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Saturday, August 23rd, 2008 AT 8:41 PM
Tiny
IAMFURQAN
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Ahh! Once again it is behaving same after running 50Km.
Now this time I have just reset the computer by removing -ve terminal of battery, and again it is running smooth. So it looks like when ever I am reseting the computer it is becoming ok for 50 to 80Km and again start behaving same. So what do you think now.
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Sunday, August 24th, 2008 AT 10:31 AM
Tiny
KHLOW2008
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What is the idling speed when it is running smooth?

Any losses in coolant level in the radiator?

The IAC seems faulty but then why should resetting cause a temporary reprieve?
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Sunday, August 24th, 2008 AT 12:16 PM
Tiny
IAMFURQAN
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Idle seed is almost 800 and once I switch on A/C it goes about 1000 for lest then second and comes down to 800 again. And no loss of lequid at all.
Tell me one thing is it posible my ECU is giving some frequesncy to IAC as per requirement of load and due to malfunction of ECU its feeding frequency to IAC changes or start fluctuating and when we requirement is reset ECU it becomes ok till again due to some internal fualt it start surging again. What makes me belive IAC is working on frequency not opening of gate as per rquirement of load is that when I checked voltages after switching on was 12volts on both terminals of input plug to IAC.
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Monday, August 25th, 2008 AT 10:14 AM
Tiny
KHLOW2008
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IAC receives power from ignition switch and the ECM will ground the other two terminals depending on engine operating temperature and conditions with various input from other sensors to control the idling speed.

The fluctuation in idling speed when AC is turned on points to a fault in the IAC or ECM.
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Monday, August 25th, 2008 AT 1:01 PM
Tiny
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Please can you tell me if I can check my ECM weither it ok or not.
So is it posible to install ECM direct from scrap for the same modle or I have to reprogram it first for my car. If I have to reprogram how can I do it.
And also can you tell me the part number of ECM, my VIN # is 1HGCG6652YA141254
Once again I am thankful to you for your time and support to me.
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Tuesday, August 26th, 2008 AT 11:17 AM
Tiny
KHLOW2008
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No reprograming is required unless equipped with immobilizer system.

You need to check the ECM part # on your vehicle and get the same from the scrap yard.

I would try replacing the IAC first, more likely to be the source.
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Tuesday, August 26th, 2008 AT 6:59 PM
Tiny
IAMFURQAN
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At last while looking around for another IAC in scrap, I met with mechanic he asured me he can fix the problem. In one day he fixed it but he is not willing to tell me what he had done to my vehical but car is running very smooth. I dont know what he had done and also I dont know weither I should be happy more or worry more. Cause I dont know what he had done. One thing I had noticed after ward I had never noticed earlier, when car is in drive and AC is one after every 60sec or so with comprassor turning on sound RPM goes to 1000 and then imidiatly come back to 800. Is it ok.
Once again thanks for your support.
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Friday, August 29th, 2008 AT 7:43 AM

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