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Old 14th January 2015, 09:26   #1
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Default Engine Shuddering Issue

My family's CNG converted Hyundai Getz has been having some issues lately. Since about three weeks ago, the car sometimes shudders while driving, especially on sudden acceleration. (Feels as if the engine is being deprived of fuel or spark).

The issue appears irregularly, sometimes the car will run fine for days until it randomly starts shuddering/missing on acceleration. This happens on both CNG and petrol.

My dad got the car checked by a nearby garage, but the issue wasn't apparent when they test drove the car. They suggested just cleaning the throttle body. As we had planned a 300km trip that weekend and the issue had seemingly disappeared we decided to get this done when we got back. The car mostly ran fine during the trip.

Today, the car again started violently shuddering on acceleration. After a while there was a high pitched scraping sort of sound which we noticed at slow speed, but we could not detect it when we stopped the car to check under the hood.

Although we will be getting the throttle body cleaning done as soon as possible, I doubt that this is the cause of the issue. I had originally thought it could be an electronic issue such as a faulty throttle position sensor or crank position sensor; but now the sound seems to suggest a mechanical problem. Anybody have any experience with a similar issue?
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Old 14th January 2015, 12:20   #2
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Default Re: Engine Shuddering Issue

Shuddering can be either due to bad fueling or bad electrical. Now since the issue happens both on CNG and Petrol, i would first check for issues in electrical circuit. Start with the plugs, then coil pack and wires. I would suggest you take it to a authorized garage for hyundai, they will be able to identify such issues faster.

Ideally use Petrol mode to trouble shoot since it would be straight forward.

EDIT: Does this happen only when the engine is fully warmed up OR happens even during cold conditions?
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Old 14th January 2015, 12:29   #3
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Default Re: Engine Shuddering Issue

Quote:
Originally Posted by RandomUsername View Post
The car mostly ran fine during the trip.
Try taking the car on another long drive while running on petrol only (not on CNG), with a dose of 1ml/litre System-G or similar, mixed with the petrol. I suspect an injector issue due to extended running on CNG.

Quote:
...high pitched scraping sort of sound ...
May be unrelated to the shuddering problem - check fan belts.

Last edited by SS-Traveller : 14th January 2015 at 12:40.
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Old 14th January 2015, 13:09   #4
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Default Re: Engine Shuddering Issue

This is usually a result of bad coils. Get them checked and replaced.
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Old 14th January 2015, 14:26   #5
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Default Re: Engine Shuddering Issue

Any warning lights, or CEL (check engine light) showing on the dash?

Even without warning ligjhts, get your car/engine hooked up to a proper OBD analyser to try and figure out what is going out. Preferably one that can do live measurements as well.

Could be anything but going by the little we know I would think electrical (maybe coil as suggested). Injector maybe, although I would think that would pop the CEL pretty quickly.

I doubt it is the throttlebody. If cleaning is the remedy there should be visual evidence of it being contaminated in the first place.

Jeroen
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Old 19th January 2015, 10:57   #6
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Default Re: Engine Shuddering Issue

An update on the issue: the problem turned out to be a loose connector to one of the sensors (probably the crank position sensor).

We also got the timing belt, the alternator belt, and the belt tensioner pulley bearing replaced, so hopefully even the scraping noise issue has been solved.
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Old 19th January 2015, 15:41   #7
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Quote:
Originally Posted by RandomUsername View Post
An update on the issue: the problem turned out to be a loose connector to one of the sensors (probably the crank position sensor).

We also got the timing belt, the alternator belt, and the belt tensioner pulley bearing replaced, so hopefully even the scraping noise issue has been solved.

If you would have hooked up to an OBD analyzer it would have shown which connector. I don't understand replacing all these parts in one go. Its very unlikely that all three of them were producing a scraping sound. I would have tried to troubleshoot a bit further. Look for obvious signs of something touching. Use a stethoscope to find the culprit. Maybe change the parts one by one.
Jeroen
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Old 19th January 2015, 19:17   #8
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Default Re: Engine Shuddering Issue

Quote:
Originally Posted by RandomUsername View Post
An update on the issue: the problem turned out to be a loose connector to one of the sensors (probably the crank position sensor).

We also got the timing belt, the alternator belt, and the belt tensioner pulley bearing replaced, so hopefully even the scraping noise issue has been solved.
Spot-on Jeroen.

Rather than changing everything at a go blindly without knowing the root cause is like shooting arrows in dark.

What if the issue repeats, no one would know the real reason as all the said parts were changed at a go!

Quote:
Originally Posted by Jeroen View Post
If you would have hooked up to an OBD analyzer it would have shown which connector. I don't understand replacing all these parts in one go. Its very unlikely that all three of them were producing a scraping sound. I would have tried to troubleshoot a bit further. Look for obvious signs of something touching. Use a stethoscope to find the culprit. Maybe change the parts one by one.

Jeroen

Last edited by a4anurag : 19th January 2015 at 19:21.
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