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Old 7th January 2008, 10:16   #16
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Originally Posted by gemithomas View Post
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.
In my Siena, whenever I switch on the a/c, the idle RPM jumps up a bit and smoothens up the idle to a good extent. But whenever the compressor gets cut-off during a/c operation, then the roughness comes back. But, I am not really sure about the headlight thing though.

Regards,
Karthik.
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Old 7th January 2008, 10:20   #17
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Originally Posted by sgiitk View Post
By the looks of it it may be an intermittent link in the HT lead. These are a pain to diagnose and very easy to fix. One option will be to (at least temporarily) replace the HT cables.

One way to check out will be remove HT leads one by one. Removing a good lead will make the idle rougher, while the bad one should make no or marginal difference.

I will be watching this thread.
I will definitely check this up. Major problem I am facing is that the mechanics at the authorized service centers are not even taking up my suggestions seriously. It will be so good if I can find a mechanic who will be able to listen to me patiently and take up the troubleshooting work in a orderly and serious manner ..
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Old 7th January 2008, 12:10   #18
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Will the issue be because of a bad fuel injector. What exactly will be the symptoms for the bad fuel injector ?
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Old 7th January 2008, 13:08   #19
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Yes it could be injector problem, 6 months back my Fiat Siena 1.6 had similar problems it was rectified to be bad Fuel Injectors (replaced all four injectors costing Rs. 1,500 per injector) since then theres no problem. but first get ur spark plugs, Battery ,Oil & fuel injectors checked.
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Old 8th January 2008, 19:15   #20
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Originally Posted by ece2k2 View Post
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.
hello
this issue may come if ur inlet valve are leak. so there is no proper combustion taking place. and ur exhaust will sound as if the car is missing. get ur compression check on all ur four cylinders.
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Old 9th January 2008, 21:19   #21
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Nice video ece2k2. The sounds were like the sweet typical diesel clatter. I faced a similar issue in my Ikon 1.6 sometime bak. Two sparkplugs were not functioning properly as well as one header was blocked. Do have the sparkplugs checked as well as the alternator for power supply due to the dimming of the interior cabin.

cya
A
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Old 11th January 2008, 21:14   #22
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Originally Posted by gemithomas View Post
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.
Yup. It idles normally when EITHER headlights OR A/c is switched ON. So i'm guessing its really doesn't have anything much to do with the headlights alone.

And you cant sum up to say it has anything to do with the Fuel Injection system either.

And those Maruti Service guys as usual shoo off the topic saying its a usual thing in all the Diesel Cars. whereas i haven't seen it happen in my pal's LDI.
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Old 13th January 2008, 01:59   #23
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Default Update - Issue seems to be fixed!

Guys,

First of all, thanks for providing your valuable inputs. After a lot of thinking, I took my car to Greentracks today as I had some hope in them for fixing my Siena's misfiring issue. After spending 3 hours, they told me that that timing has gone bad. They have fixed it and the car idles really smooth now. But, I was charged 850 bucks for timing adjustment. Am not sure if this is on the higher side, but worth the hassle.

So, the source of the issue is that the Prerana Motors service people had goofed up my car's timing when they were fixing the other issue

One more thing is that Shivram at Manipal Motors told me that the shocks are weak in the car and need to be replaced, when I reported a rear end noise issue when the car is fully loaded with passengers/luggage. Greentracks (Javali motors) guys told me that the shocks are fine and it is just the lack of lubrication in the suspension system. Don't know whom to believe.

Now I am really not sure if I should go to the Tata ASC for even regular oil service ...

Regards,
Karthik.

Last edited by ece2k2 : 13th January 2008 at 02:03.
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