Problem with Vtec idling...varying RPM. EDIT : Solved!

[Rtech]

I wonder if it is actually carbon of lousy fuel gumming up??

[GTO]

Yup, thats what Monkey called me up to say. He had a similar issue with bad fuel in his vRS.

[shrivz]

Originally Posted by GTO

Well, it was actually a smaller problem than I thought. No problem with the sensors or anything......there was carbon build-up on the throttle body.

I sent the Honda over to Arya Honda, since I am very happy with the service Shaman (same group) has given my Indigo. They cleant it up on the same day and car is back to smooth purring.

Thanks for all the help, guys!

Well, I got my throttle body cleaned a few days back, but the problem hasnt got solved!

But then again, it could probably be the fuel!

[triggercool]

I had same problem with my Honda Vtec. Detected O2 sensor

[veyron1]

Originally Posted by Rtech

Maybe they meant the same thing as mentioned here...dirty MAF sensor.

Don't you mean MAP? VTEC is N.A.

[chetanhanda]

Originally Posted by GTO

Well, it was actually a smaller problem than I thought. No problem with the sensors or anything......there was carbon build-up on the throttle body.

I sent the Honda over to Arya Honda, since I am very happy with the service Shaman (same group) has given my Indigo. They cleant it up on the same day and car is back to smooth purring.

Thanks for all the help, guys!

You had mentioned you had noticed higher rpms upto 1500.
Definately this was due to excess air during idle, so the leakage of excess air was due to the Throttleplate being partially stuck open due to carbon deposits.
Right ? how else will RPM shoot up to 1500 without air leakage ?
just want to know exactly what happened ..Im curious..

[Rtech]

Originally Posted by veyron1

Don't you mean MAP? VTEC is N.A.

Does a OHC use a MAF or MAP? Don't know. But what does it being NA have to do with it?

[narayan]

Originally Posted by sushrutha

I'm new to OHC.
Every morning when I start my OHC 1.3Exi , my car RPM needle raises till 1,300RPM and after 1 min or so it comes down to 750 -800 Rpm mark.
Is this normal ?

thats perfectly normal....

[narayan]

Originally Posted by GTO

This had happened about two months back, but rectified itself automatically. However, since this morning, the problem has resurfaced.

At idling, the RPM keeps on shooting between 800 - 1500 rpm by itself. The car has completed around 52,000 kms and most of you know the minimal mods I have put on it. I didnt want to take a chance so just parked her back in the garage.

Whats up?

had the same problem after i replaced my O2 sensor...

got solved when the service guys checked all the connections and said there was a loose link - they fixed it - reset the battery and all was fine.....

in fact i had this problem even when going slowly in 1st gear and suddenly loss of RPM

[chetanhanda]

Originally Posted by Rtech

I wonder if it is actually carbon of lousy fuel gumming up??

definately Carbon buildup due to blowby, the EGR allows exhaust gas to flow thru the TB, and EGR gas becomes more damaging if the engine is not burning fuel perfectly

fuel wont be able to gum the Throttlebody,throttleplate or even the IACV.
There is no contact with the fuel... why are you having this doubt ? the injectors are further downstream...

[veyron1]

Originally Posted by Rtech

Does a OHC use a MAF or MAP? Don't know. But what does it being NA have to do with it?

MAF is for boost applications, dear Robeen...

MAP sensor is that tiny black sensor on the manifold tube. MAF is situated at the TB end for boosted cars...the big black thingy with the circlip..

Nevertheless. I still do not understand how a dirty TB would affect the idling. Perhaps a dirty checkvalve/Idle Air Control Valve, but....

@chetanhanda; A faulty Ignition Control Module would cause cylinder missing/misfire, which would show up throughout the rev range, na...not just idling, right...

[chetanhanda]

Originally Posted by veyron1

MAF is for boost applications, dear Robeen...

MAP sensor is that tiny black sensor on the manifold tube. MAF is situated at the TB end for boosted cars...the big black thingy with the circlip..

Even NA cars have MAF sensors, where did you get this idea that NA cars have to be MAP , some stock cars even have Alpha-n ...You cant make a rule NA= MAP..

Originally Posted by veyron1

Nevertheless. I still do not understand how a dirty TB would affect the idling. Perhaps a dirty checkvalve/Idle Air Control Valve, but....

Exactly opposite of what u are saying : dirty IACV etc should create a low idle not a fast idle as it is not supplying enough air toidle at 800rpm
if ur Throttleplate is not closed completely due to some carbon crap , it will contribute to the air supply provided by the IACV...

Originally Posted by veyron1

@chetanhanda; A faulty Ignition Control Module would cause cylinder missing/misfire, which would show up throughout the rev range, na...not just idling, right...

nope, some misfires/missing are not detectable when revving higher, but more noticeable during idling.

[Ford Rocam]

Originally Posted by chetanhanda

Quote:
Originally Posted by veyron1 (Problem with Vtec idling...varying RPM. EDIT : Solved!)
Nevertheless. I still do not understand how a dirty TB would affect the idling. Perhaps a dirty checkvalve/Idle Air Control Valve, but....

Exactly opposite of what u are saying : dirty IACV etc should create a low idle not a fast idle as it is not supplying enough air toidle at 800rpm
if ur Throttleplate is not closed completely due to some carbon crap , it will contribute to the air supply provided by the IACV...

.

There is something like Throttle Position Sensor or (T.P.S), a variable resistor connected to butterfly of throttle plate, when throttle is closed it generates "x" voltage say for eg: 0.45V that value goes to ecu as throttle is closed & the engine should idle so it activates I.A.C valve to routine idling operations. If there is dust accumulated due to carbon buildup the throttle will not fully close & the T.P.S sensor will think as if throttle is slight open & o/p voltage will be different & ECU cuts off IAC valve since throttle is closed the engine doesnt gets enough air for idling & tries to die down, an abnormal state the ecu detects this abnormal condition & reactivates iac to keep engine running so engine is getting air from IAC & through small opening near t.b which is not fully closed causing weired idling.

This is also a common problem observed with people who have enlarged their T.B, if T.P.S is not calibrated properly for fully open/fully close to stock value of TPS volatge w.r.t stock T.B you will notice all kind of weird issues wrt idling & part throttle driving.

[GTO]

Umm guys.......the revv limiter is not kicking in at 7100 rpm . And it isnt one single instance. I had three separate runs on the way to work this morning. She is revving upto 7400 rpm. I didnt have tarmac to take it further but even at 7400 rpm, the limiter didnt kick in. The first time it happened, I thought it was my mistake in reading the gauge. So I tried again, and yet again. The rpm is going uptil 7400 - 7500 and still the limiter is not kicking in.

Psycho says this is due to the ECM reset. Whatever it is, who is complaining ?

BTW, with reference to the idling problem....I spoke to the techie again and this is what he has done: Cleant sensors, cleant TB and reset ECM. It has to be one of these since the idling is butter smooth now.

[Rtech]

Originally Posted by chetanhanda

Even NA cars have MAF sensors, where did you get this idea that NA cars have to be MAP , some stock cars even have Alpha-n ...You cant make a rule NA= MAP..

My question as well Atul! What made you conclude that only forced induction vehicles would use a MAF sensor?