Team-BHP - Rough idle and exhaust note not smooth

Guys,

This rough idle issue has been in my fiat siena 1.6 for the last 5 months and it has been really irritating with the roughness (light constant shaking during idling) coming into the passenger cabin. The exhaust is also not smooth when idling and its note is pretty rough like misfiring. This issue started when I gave my vehicle for service (for a different issue) at Prerana motors. When I reported this issue to the Prerana Motors service person during the vehicle delivery, I was told that the issue may be because of carbon buildup. They tried the following for fixing this up (for a bill of Rs.4000+):

1. Ignition coil
2. Spark plugs
3. Engine De carb
4. Engine diagnostics - no errors

At that point I could understand that they were taking me for a ride and got the car back. After all the trials, Prerana mechanics even tried convincing me that the car is idling fine, when I could feel the roughness very well ...

Three weeks back, I detected that the fuel filter has got damaged (petrol leaking) and replaced the fuel filter.

When I left my car for service at Manipal Motors last week, I was told that the culprit for rough idle may be Oxygen (lambda) sensor. Shivram (Manipal motors service advisor) told me that the lambda sensor need to be ordered from Fiat and it may take a few days for him to get it.

I have tried myself the following stuff:
1. Drove the car till the fuel tank became empty and refuelled at a couple other places. Just to make sure that the issue is not because of bad fuel quality
2. Added Bardahl injector kleen

Both the above did not really work. When I switch on the a/c the roughness reduces a little. I also felt that the engine is missing a beat at times when I accelerate - may be a related issue???

Pollution check did not give any extreme results (slightly higher pollution level as compared to last time) but the pollution is still under control. The mileage also has not dropped drastically. From my searching the internet, I saw that the Oxygen sensor failure will cause the pollution check to fail and worst fuel efficiency. Since these are not there, I am really doubtful if I need to replace lambda sensor.

I do not want to go through another iteration of "trial and error" by service center. Please give your expert guidance to fix this up.

Thanks.

- Karthik.

hey there, mine is an SX4, june 2007 model, ever since i bought it i feel that the overall feel of the engine, ie, the roar of the engine (both at idle as well as under acceleration) is quite rough and the car overall is pretty 'old diesel like rough' to drive. Both the mileage and the pickup are bad.

i tried showing this problem to a few M.A.S.S in delhi, but to no avail, they always discard it saying that's its just my 'vehem' (incorrect mental feeling)..so i went ahead and taook a test drive in one of the Demo cars in a south delhi maruti showroom..and voila ! The car, despite being a neglected and badly abused test drive vehicle..was running very very smooth with greater pickup. Its acceleration, idle etc everything was so damn smooth !

Somebody has advised me to stop using premium fuels and get the car checked at the Maruti owned Sales and Service at naraina..its got its own team of very well trained engineers appointed by Maruti Udyog India. LEts wait and watch ! Would appreciate your views ! Thanks !

Kadam/Humyum/Friends,

I tried capturing the video of the car rough idling today morning. I have uploaded them in youtube. I will be thankful if you guys could hear it once and give me your feedback.

Ticking noise captured from under the engine bay (Kadam sir, is this the one you were mentioning as kit kit noise???) :
YouTube - Siena 1.6 rough idle - ticking noise

Rough exhaust note - seems like the exhaust is coughing out the smoke:
YouTube - Siena 1.6 rough idle - exhaust note

Dashboard video when the vehicle is idling with RPM meter focussed:
YouTube - Siena 1.6 rough idle - tachometer and interior noise

Please check the sound from the video as the video is not very clear. I am sorry for not using a sound recorder and instead using a camera - audio recorder option would have made the file sizes smaller, but I do not have a exclusive sound recorder unfortunately.

Regards,
Karthik.

I think i see your rpm meter at 750 mark. SHouldnt this be at the 850 mark when in idle? cant make out if it is vibrating. And is your light also dimming (since you focused on it on your video).

I'm Not good with the technicalities. But these are the things i think you should check.

I think there is something like a EGR (somehting to do with gas recirculation) which if not functioning properly could lead to irregular idling. Check the EGR valve and any sensor for this purpose.

But that "tick tick" sound that is heard makes it look like something mechanical and not electrical. Anyways let wait for responses. HAve you posted this on the PUG/fiatclubindia. Guess you would get more specific user responses there

Please do let us know once it is solved.

Quote:

Originally Posted by gemithomas (Post 679238)

Hi Gemi,

Both Prerana and Manipal Motors guys hooked up the ECU diagnostic monitor and said that there is no error. Prerana guy specifically checked for the idle RPM through the monitor and verified for the correctness of it. Another thing is that the Prerana mechanic told me that the EGR valve is not present in Fiat 1.6 engine - not sure if this is true ? Yeah, you are correct - I focussed on the interior light to show that there was the momentary dimming in the cabin light when the engine was rough idling, which did not come up well in the video clip.

I am planning to post this in the Indian PUG soon.

Regards,
Karthik.

Quote:

Originally Posted by ece2k2 (Post 679379)

Just a thought. Have you checked the alternator. Maybe its sending varying current all over!!

But its that sound that gives me a feeling of some mechanical problem. There is a bearing for the timing belt. Get that checked too. Hope you get it solved ASAP. It feels so frustrating when the mechanics are unable to even identify the correct problem.:Frustrati

Quote:

Originally Posted by callnishanth (Post 679323)

Im havin the same problem with my SWIFT VDi... Use only Shell Diesel... Switch off the headlights / AC and the car starts shaking for the variation in rpm... varies from 800 to 850 constantly during idling...

Is this some kinda electric or battery related problem???

What about when the a/c and lights are on. Does it idle normally in such a case. I've heard of it the pother way round but not something like this. I think there is thread on an alto which used to behave like this when the headlights were switched on.