[swarnava.m]

The chauffeur pointed this out to me, and then I verified this myself.

Twice in the recent past, the car has failed to start when cranked. And this is not a cold start/early morning start, would be anytime around the afternoon, during regular use, while trying to start maybe after 30 mins or 1 hour of stoppage. I got the battery checked, and the report came good. So battery problem ruled out. It is difficult to reproduce the problem at will, but I am concerned about getting stranded in the middle of the road with such a problem.

Another issue, though I don't know if it is related to the above problem, is that while at a standstill, gear in neutral, I started revving the throttle. When it reaches 4k RPM, it does not go any further. Instead, the RPM starts fluctuating. What I actually mean is that, for half a second it drops by about 400-500, then returns to 4K. This phenomenon keeps repeating every 3-4 seconds. However, anything below 4K RPM, and everything seems fine.

I am yet to visit Honda for these issues, but would like some help/suggestions from the Gurus here first.

For the record, its a 2.4L MT, 2 years old, 51K running. Thanks.

[Jaggu]

Problem 1- check the cables and the starter if your battery is fine.

Problem 2- Hope its not the vtec unit playing around, how does it respond while in gear and accelerating. You can engage 1st gear and check in a non crowded street/area.

[vigsom]

Please get an engine scan done - in all probability the issue is with the Throttle position sensor(TPS)

Just cleaning the throttle body should solve the problem ; when was the last time it was done?

[ecenandu]

Originally Posted by swarnava.m

Another issue, though I don't know if it is related to the above problem, is that while at a standstill, gear in neutral, I started revving the throttle. When it reaches 4k RPM, it does not go any further. Instead, the RPM starts fluctuating. What I actually mean is that, for half a second it drops by about 400-500, then returns to 4K. This phenomenon keeps repeating every 3-4 seconds. However, anything below 4K RPM, and everything seems fine.

You can rule out this one. It is not an issue, Honda has limited the revs upto 4000rpm in neutral gear. The drop in rpm is due to the rev limiter trying to keep the rpm well below 4000. I have done the same in my Honda City iVTEC. It doesn't rev above 4000 in neutral.

[ilangop]

Originally Posted by swarnava.m

Twice in the recent past, the car has failed to start when cranked. And this is not a cold start/early morning start, would be anytime around the afternoon, during regular use, while trying to start maybe after 30 mins or 1 hour of stoppage. I got the battery checked, and the report came good.

Swarnava, The symptoms you have mentioned hints me of some thing similar to vapor lock in carburetted cars. Do you feel any surge in acceleration while you suddenly depress acc pedal? Get to a service centre and check for the fuel pressure & engine vacuum values. Also check for leaks in the vacuum lines.

[Jaggu]

Originally Posted by ecenandu

You can rule out this one. It is not an issue, Honda has limited the revs upto 4000rpm in neutral gear. The drop in rpm is due to the rev limiter trying to keep the rpm well below 4000. I have done the same in my Honda City iVTEC. It doesn't rev above 4000 in neutral.

Yes this is what i mentioned, in the vtec engines the rpm has lower cut off while in neutral IIRC. Only way to confirm is to do this while driving, to get higher rpm safely, use the lowest possible gear in a deserted area. At 4-4.5 k rpm, the Vtec should open and you should get the surge thats all.

[swarnava.m]

Originally Posted by Jaggu

Problem 1- check the cables and the starter if your battery is fine.

Problem 2- Hope its not the vtec unit playing around, how does it respond while in gear and accelerating. You can engage 1st gear and check in a non crowded street/area.

Yes, I will do that today, checking the cables and starter.
As for 1st gear, it behaves absolutely normal. No issues there.

Originally Posted by vigsom

Please get an engine scan done - in all probability the issue is with the Throttle position sensor(TPS)

Just cleaning the throttle body should solve the problem ; when was the last time it was done?

Quite recently actually, about 8 months back if I am not wrong. Will check the service log book for this.

Originally Posted by ecenandu

You can rule out this one. It is not an issue, Honda has limited the revs upto 4000rpm in neutral gear. The drop in rpm is due to the rev limiter trying to keep the rpm well below 4000. I have done the same in my Honda City iVTEC. It doesn't rev above 4000 in neutral.

Okay thanks. I guess that solves the issue right there. Thanks a lot!

Originally Posted by ilangop

Swarnava, The symptoms you have mentioned hints me of some thing similar to vapor lock in carburetted cars. Do you feel any surge in acceleration while you suddenly depress acc pedal? Get to a service centre and check for the fuel pressure & engine vacuum values. Also check for leaks in the vacuum lines.

Didn't exactly understand what you are asking there. I mean yes, when I suddenly depress the acc pedal there is a surge in acceleration, and I would say that is normal, as per expectation. Is this not supposed to be happening? I do not see why..

Originally Posted by Jaggu

Yes this is what i mentioned, in the vtec engines the rpm has lower cut off while in neutral IIRC. Only way to confirm is to do this while driving, to get higher rpm safely, use the lowest possible gear in a deserted area. At 4-4.5 k rpm, the Vtec should open and you should get the surge thats all.

Alright thanks. I will do this and verify the same. Thanks a lot for your inputs, I guess this is a non-issue now.

[ecenandu]

Originally Posted by swarnava.m

Twice in the recent past, the car has failed to start when cranked.

Then how did you manage to get the vehicle started in those two situation?
Do you mean, the vehicle is not starting in the first crank or not at all (after repeated cranks).

[swarnava.m]

Originally Posted by ecenandu

Then how did you manage to get the vehicle started in those two situation?
Do you mean, the vehicle is not starting in the first crank or not at all (after repeated cranks).

He couldn't. Yes it was not starting after repeated cranks also. So he switched off everything, waited for about 10 minutes, and tried again. Then it started.

Another thing the driver told me is that both the times that the car refused to start, the temp gauge needle on the console was down all the way to C, when it actually should have been somewhere midway since the car was used prior to that. Then when it actually started, the needle was pointing where it really should.

[ecenandu]

Originally Posted by swarnava.m

He couldn't. Yes it was not starting after repeated cranks also. So he switched off everything, waited for about 10 minutes, and tried again. Then it started.

Another thing the driver told me is that both the times that the car refused to start, the temp gauge needle on the console was down all the way to C, when it actually should have been somewhere midway since the car was used prior to that. Then when it actually started, the needle was pointing where it really should.

Oh OK. Please update us once the problem is solved. Just curious to know who is the actual culprit.

Just a wild guess, does it mean that ECU is not powered up. Anyways, next time if you happened to be there when it occurs, please try to switch on and off the ignition key, check out for a fuel pump noise. Normally once you switch on the ignition key and ECU is powered up properly, the fuel pump will be on for few seconds. If you are not able to hear the pump noise, that means ECU is not powered up. Oops being a executive sedan, I think they would have done enough sound insulation so that the fuel pump noise is filtered out. This is how we found the starting trouble for a Royal Enfield 500cc FI, but then it was an Enfield and this is Honda. Never mind.

There are umpteen other reasons for the vehicle not starting, please update us once the issue is solved.

[v&v]

Originally Posted by swarnava.m

He couldn't. Yes it was not starting after repeated cranks also. So he switched off everything, waited for about 10 minutes, and tried again. Then it started.

Another thing the driver told me is that both the times that the car refused to start, the temp gauge needle on the console was down all the way to C, when it actually should have been somewhere midway since the car was used prior to that. Then when it actually started, the needle was pointing where it really should.

I think the main relay is malfunctioning when hot and is causing starting issues.
hope this link should give some good info. http://techauto.tripod.com/

[bejoy]

Originally Posted by swarnava.m

And this is not a cold start/early morning start, would be anytime around the afternoon, during regular use, while trying to start maybe after 30 mins or 1 hour of stoppage.

An ECU scan would hopefully throw up an error. Worth to get the RPM (a.k.a. Crank/TDC) sensor checked.

[Rovergen]

If engine does not start (though all fuses are in place) but the the starter motor is working then there is a very fat chance that it is the crank sensor playing havoc , the best way to check it is open your spark plug connector wire , insert the screw driver ( into the socket ) ask some one to crank the engine when you move the conector and screw driver near any metal surface if you do not get spark then it is the crank sensor - Ver crude way but worked for me , Though ECU check would tell all this .

[swarnava.m]

Thanks to all of you.. As it turns out, I guess my best bet would be to take it to Honda and have them run a diagnostic scan. Will report the results after I get it resolved, which, unfortunately, will not be before next week.

[swarnava.m]

UPDATE: I did take the car to Honda. They ran a scan, and everything was reported fine. No errors showed up on the scan.

Also, the issue has never resurfaced. So its hard to say what causes it now, I just hope I have seen the end of it. Also hope that there is no underlying problem, and does not cause any issues in future.