Missing on Fiat Adventure

[gemithomas]

Hi guys, i had poster this earlier on different forums so some of you guys might be aware of this problem of mine.

The issue is that the 1.6 engine misses a heartbeat every once in a while. I have been noticing this for some time now and i have seen that wenever this happens the rpm would be somewhere between the 1300-1500 mark. But the funny thing is that this does not happen every time i cross this rpm. so have not been really able to find out whether there is any specific pattern in which this occurs. The engine just misses a beat and there is a minor jerk after which everything is perfectly normal.

I normally dont push the car much especially while driving in the city and i usually engage 5th as soon as i cross the 40-45km/hr mark. 4th gear comes at around the 30-35km/hr mark and the vehicle pulls along without any difficulty. On higways though i push her a little more and normally would be doing around 90-110km/hr. On highways since i am mostly at the higher rpm ranages, this issue is not that evident. So i assume that this problem does not happen at higher rpm ranges.

Petrol used has always been the higher end versions like speed and xtra premium. Last week i also tried Power for the first time to know if it would make any difference.

Last week connected the vehicle to the diagnostics unit at the A.S.S and found no errors on the ecu. As i had expected they said it mostly ahppens because of the fuel and added some additives to the petrol and asked me to check it out for a while. I am Yet to confirm if there has been any difference. But my logic tells me that its not anything to do with the fuel since i see the 'skip' is always at some particular rpm.

I have got responses from users that i could be a faulty sensor, throttle body or an ecu. I dont want the "Authorised " tata guys to conduct their experiments on my vehicle. I talked to them but they did not know about any particular sensor that could be causing this problem. And since the ecu was not showing any errors they'll have to start checking it from one end. From all my "very good"(hmm!!) experience with the old TVS guys, i'm sure i dont want the tata guys to start it all over again and end up in spoiling the whole fun of driving. I would like to have a real good idea of all the aspects before i let them put their hands inside my engine bay.

[moralfibre]

Hi gemithomas, this is normal behaviour and happens with my car too. I have driven a few GTX's which also exhibit this jerk. Someone told me that it happens when the ECU advances or retards fuel flow depending on the quality of fuel. Dont worry its not a major issue it happens in my car too.
If you notice jerks which are very light and continuous and barely perceptible in traffic then its a throttle body issue and you must get it replaced in warranty. This is a problem with etchemkays car and he will be getting a new throttle body soon.

[tsk1979]

Faulty EGR valve?
Could be stuck . Does you car stall too occasionally at low RPMs?
Try getting your fuel filter checked too.
These are the only two things I can think off which can cause this problem.

It could be a clogged intake manifold too, but that will cause problems in pickup etc., too. I suggest you get these things checked in front of you at a workshop.

[hrag]

gemithomas, I think you're shifting up too early. Take the engine to at least 2000 rpm in each gear before upshifting.

[Jaggu]

hope you are shifting atleast after 2 to 2.5 k, please understand that any car engine requires a min rpm to pull it, and more harm is caused if you try to unnecessarily load the engine in low revs than revving it a lil more.

Assuming your gear shifts are normal, second check can be fuel filter that can be a culprit, if not proceed to spark plugs and wires (yes failure, loose connections can happen in brand new parts also)

If all of the above is fine, then check the injectors, but in your case i really doubt this can be the issue.

Finally if this is a part and parcel of fiats then you need to get in touch with the manufacture service manager for the territory.

[tsk1979]

Umm I disagree with all the above inputs given.
Reason, no matter where you shift the engine should not miss. Ok you shift too early, you stall, or you knock, but missing. That means a misfire. Low RPM misfire is normally linked to EGR valve which is a troublesome piece of equipment in any car, be it petrol or diesel.
If lots of Palio/Adventure petrols are having this, this could be a design issue.

So if your car misfires, don't accept it as it is, fight.
Back in 2003 whereabouts a friend of mine got a petrol indigo. Shifting to 4th at around 45kmph(recommended by Tata itself for FE) would result in a slight judder(not misfire).
The acceleration at low RPMs was juddery.
They kept on stalling him saying all cars have this, but he hung on, calling regional center and what not, and eventually his problem was solved. It was a common problem(something to do with ECU software) and was fixed in later batches.

So that attitude "Common problem, happens in all cars" is not really healthy.

gemi, one question to you, do you notice missing if you slow accelerate from idle to 1500rpm in neutral?

[Jaggu]

what if it is engine shunting with low rpms and not missing as "termed"? can we over rule that??

ok do this check, at idle slowly rev the engine from 1000 to 2000, see if there is a "missing" anywhere, if it is really missing then it can be pin pointed to the dealer also this way.

[tsk1979]

It happens only sometimes, not always. If it was low rpm reason, he would feel the judders every time if shifting too low.
45kmph for 5th gear is okay in most petrol cars and even in diesels if you are not going up an incline.

[Jaggu]

Originally Posted by gemithomas

so have not been really able to find out whether there is any specific pattern in which this occurs. The engine just misses a beat and there is a minor jerk after which everything is perfectly normal.

Do the above check to find defenite pattern if any.
"minor jerk" is what makes me think that it might be low rpm shunt.
And no for a heavy car like adventure even with a torqe engine like 1.6, 45 km/h for 5 th gear might be cutting it too close is what i feel.

[gemithomas]

Thanks a lot for all the very quick responses.

I was always of the impression that uncessary revving was bad for the engine. The Fiat 1.6 engine pulls really well from very low as 1100-1200 rpm. I can quite easily shift up at as low as 1500-1600 rpm and yet the engine pulls so efficiently that i've never felt its under load. So in city i try shifting at these rpms as far as possible since i've heard that this would get me more F.E figures. I have never felt the need to go above 1800 rpm for an upshift on this engine. Could anyone confirm if its ok to shift at low rpm's if the engine does not show any signs of being over burdened.

I have never felt the knock and the engine has never stalled. I have also tried accelerating in idle from 1000 to 2000 rpm just a few times but could not feel this 'missing'. Will do that some more times to get a feedback.

What does the EGR valve do. Could you explain this. And if its a problem with this thing would it happen at a particular rpm.

[tsk1979]

Exhaust gas recirculation - Wikipedia, the free encyclopedia

From the article

EGR is typically not employed at high loads because it would reduce peak power output, and it is not employed at idle (low-speed, zero load) because it would cause unstable combustion, resulting in rough idle.

[chetanhanda]

Originally Posted by tsk1979

Try getting your fuel filter checked too.

I agree to this ..I think clogged fuel filter, injectors etc could be a problem ...
Does this happen when the fuel tank is at low level ?

Originally Posted by tsk1979

It could be a clogged intake manifold too, but that will cause problems in pickup etc., too. I suggest you get these things checked in front of you at a workshop.

I dont think it could be a clogged intake manifold.
Can an Intake manifold get clogged so much ? Airfilter wont let in so much dirt that intake manifold starts getting clogged ..

Originally Posted by tsk1979

Faulty EGR valve?

IM not sure if EGR will cause such noticeable missing ?
It may cause loss in power etc may even cause pinging and knocking as a main symptom,along with high engine temperatures also.

Best way would be to see the exhaust emissions from a local testing facility, the NOX emissions should be high if it was an EGR issue.

But these symptoms of engine missing dont sound like an EGR issue to me.

[tsk1979]

Originally Posted by chetanhanda

I dont think it could be a clogged intake manifold.
Can an Intake manifold get clogged so much ? Airfilter wont let in so much dirt that intake manifold starts getting clogged ..

Faulty air filter can cause all dust getting sucked in. I have seen clogged intake manifolds and gotten them cleaned too

IM not sure if EGR will cause such noticeable missing ?
It may cause loss in power etc may even cause pinging and knocking as a main symptom,along with high engine temperatures also.

Best way would be to see the exhaust emissions from a local testing facility, the NOX emissions should be high if it was an EGR issue.

But these symptoms of engine missing dont sound like an EGR issue to me.

No emission problem you see. By faulty I meant always operating. In petrol's EGR is supposed to be "off" at idle and "high" loads. If thats not the case there will be erratic idle, and missing at high load.

His problem may be EGR valve open at idle while it is supposed to be off.

[gemithomas]

It is not anyway related to the amount of fuel. I have checked that. Even when its on a full tank, this thing happens.

Regarding a clogged intake manifold, Dont you think that this would affect the power delivery at all times. Logically i doubt if this would lead to a jerk at a particular rpm. Even a Fuel filter problem should not normally give me such a problem. Isnt it?

Will a faulty EGR valve give erratic idling. In that case, my vehicle is very smooth at idle. I'v heard that the EGR comes on at aroung 1500rpm on the Fiat 1.6 engine. But there again my problem is slightly below this rpm. But just thinking. Could it be somehting likethe EGR opens up a bit early. Is there some sensor that is responsible for activating the EGR.

Another thing that i have noticed is that i am most of the times on small slopes when this happens. Yet to confirm this. But i just have a feeling that it is happening more when i am on small slopes. Dont know whether it makes ay sense though!!

[Jaggu]

how many kms have ur car done gemi?