Need Advice: My 2009 Hyundai Santro stutters under acceleration

The jerk seems to be uneven and doesn't occur when accelerated in neutral gear.

BHPian Tamarind recently shared this with other enthusiasts.

Hello BHPians,

Mine is a 2009 Hyundai Santro, has done 1 lakh km. Been servicing it every ~6 months and am quite happy with the car. The vehicle has taken us places and been holding my trust till now

Last week when I had taken it over an 80 km drive on a bypass, avg speed could have been 90+ and all was fine.

I exited the highway via the two 180-degree bends in the shape of "S" (probably @ 40 km/h) to join another highway, when I pressed the accelerator the vehicle started to stutter. (During this entire drive the road was not bumpy neither did I put the car in a hard spot at high speed).

I immediately looked at the dash for engine temp, or any hazard lights - all seem to be fine. Tried switching off the AC and accelerating the effect seems to be the same.

Parked the vehicle in a calm spot and took a look under the hood for any leakage to the ground - None. Checked the oil dipstick and it had a sufficient level (F mark).

The engine bay though had a little wet oil spread on top of it, but that was an observation from earlier service as well and the mechanic said in the next service he will apply some paste in between the layers to stop that oil seepage but nothing bad to worry about.

The jerks seem to be uneven (I could not find a common time gap between two jerks). Putting the gear in neutral and accelerating does not produce any jerk.

Took the car to the nearest Hyundai service, and they checked the following

• Spark plugs
• Air filter
• Throttle body
• Ran the computer checks for Electronics,
• Smoke colour and exhaust pipe,
• Petrol pump, tank and filter for blockages, also
• A suspected mix of petrol + water but later ruled out.

But since they were not able to find the issue, they suggested replacing all the following one by one to test and isolate the issue

• Spark plugs
• Card wire
• Ignition coil
• Idle speed actuator
• Fuel filter

But since they told me it's going to take multiple days to get all parts, and also said it can be driven (ignoring the jerks) - I decided to bring it to my mechanic close to my house (with hazard lights on and driving slowly)

He inspected and changed all 4 spark plugs - instantly the jerk frequency and intensity reduced. But still not completely gone.

The mechanic says it can be the fuel pump (which has to be replaced and checked ~4k, followed by a few other items costing ~24k) and then the crankshaft to be checked. Then I told him the timing belt change is due from the last service (1 lakh Km) for which he quotes around Rs 6k

So a total of ~30k worth of parts & labour was quoted.

He also says the rear left bush has worn out and the wheel gives a thud sound on minor bad roads (which is true in my observation as well) - though it's not related to this problem, it needs a change for a bump-free ride. This might cost around 6k

The vehicle condition is good otherwise

Question:

1. What do you guys think about the above?
2. Could the jerk be due to the old timing belt? or possible oil seepage on the belt could cause the skipping bite?
3. Your suggestions based on prev experience, on which direction to take in addressing this issue?
4. Possibly a time to exchange for a new vehicle?

Here's what BHPian MT_Hyderabad had to say on the matter:

There is a sensor on the throttle body, check that.

Throttle body cleaning may be necessary, get it cleaned. These are the two things, which are not that costly and provide an easy fix.

I encountered such jerks in my car when it was 25k km old and after many deliberations, they were attributed to the loose connection of that sensor.

Here's what BHPian vrprabhu had to say on the matter:

I think the service centre has given the correct route(!), which I suggest modifying this way (based on my experience of owning a car aged similar to yours):

1. Check and replace spark plug wires (you have already changed the plugs); check whether the accelerator pedal and cable are operating smoothly
2. Replace fuel filter
3. Replace the timing belt (if not done earlier - you have a 10+-year-old car with 1+ lakh on the odometer and the belt would be showing signs of wear & tear plus slack)
4. Check and replace the sensors (MAF/O2) if the wires appear to be brittle/aged
5. Check the Ignition coil
6. Check the fuel pump

Presume that idling is OK (i.e. not erratic) and the electricals are in good condition.

Here's what BHPian bejoy had to say on the matter:

The same issue was observed in my dad's 2005 Santro. The engine would stutter and die after a spirited drive, with no throttle response. After switching off and cooling, the car would become normal. The issue got resolved after changing IAC (Idle Air Control) valve. The OEM part is expensive, I got the part from Aliexpress, cost less than 1k. It is 4 years now and the issue has not happened again. Worth getting it checked.

There is this thread on this issue.

Here's what BHPian Rahul Bhalgat had to say on the matter:

1. Try injector cleaners like Addon P. You might be aware that these are to be put in the fuel tank in a certain proportion. Consume two tankfuls. Clogged injectors may cause uneven stuttering. This will hardly cost anything and won't be a waste anyway.
2. If new sparkplugs reduced stuttering, new coils may eliminate the same. See if your mechanic can try replacement coils from some other vehicle, just for trial. And anyway, changing the ignition coil at 1 lakh km isn't overkill. I changed the coils in my SX4 at 1.25 lakh km even though I did not have problems. The old coils are preserved as spare.
3. Worn out timing belt will cause more severe problems like loss of compression and engine stalling. And once the belt slips, it is not going to align itself again to a perfect position, so the problem will be experienced all the time.
4. Santro is a very good vehicle with a very good engine. Yours will be Santro Zing I guess. It shall easily last beyond 2 lakh km if it has been maintained properly. So no need to change the car just for stuttering.

I don't know about Chennai. But Mumbai has a large population of Santro in the taxi market. If Chennai too has Santro taxis, a typical garage that services them (very few are likely to visit the authorised SS) shall be able to diagnose the issue outright.

The fuel pump could also be the culprit. But throttle body is unlikely to be the problem. By the way, do you observe any connection between low fuel levels and stuttering?

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