Team-BHP - Tata Harrier shaking & bouncing at idle (randomly)

@MODS: I couldn't find relevant threads, hence started a new one. Feel free to merge if there's any existing thread.

Greetings experts!

I've recently purchased a pre-owned Tata Harrier XT (Dec 2019). The car runs fine for the most part - no niggles as such.

But there's very intermittent issue that I face - very very randomly (like once in a month or so) the car shakes at idle. Please don't confuse this with "vibrations at idle". When I say shake - I mean the car literally bounces at idle. Let me try to describe the shake - it's like you're driving on rumbler strips at very low speeds OR you're standing still & someone is jumping in the car.

When this happens, the car shakes around 4-5 times a second. It's been around 4 months since I purchased this car & I've seen this issue 5-6 times till now. Till now the issue has only occurred during deceleration & coming to a halt (traffic signal or an intersection on the road). No CEL on the dashboard at this point. Also, whenever this occurs, a gentle dab on the A-pedal makes the shaking go away.

When I search for "engine shake" online or on the forum, mostly the "vibration" results show up & the usual suspect is clogged injector(s). To rule it out, I tried Liqui-Moly Super Diesel Additive last month, after which the intensity of the shaking has reduced a little bit. But it's still there.

Since this issue has only happened on intersections/traffic signals, I didn't get a chance to open up the bonnet & look at the engine. I tried my best to replicate the problem in my parking lot, but I could never do so.

Can the experts here shed some light on what could be this cause?

Thanks!

This is based on my personal experience. Back when i had my Verna, i faced a similar problem. I start the car and immediately the vibration was clearly observed.
Upon inspection, found that there was a rat bite and it had bit the ECU wires going into the Engine. Just one of the wires.

It appears this led to some timing issues in the engine and most likely the pistons we off sync and this led to the Vibration.

After getting the wiring fixed and ECU reset, things were back to normal.

One more point, the Engine/ECU warning light did glow for me when i faced this problem.

This might not be the exact problem you are facing, but food for thought.

Quote:

Originally Posted by vinay.sathyan (Post 5534099)

I start the car and immediately the vibration was clearly observed.
<SNIP>
It appears this led to some timing issues in the engine and most likely the pistons we off sync and this led to the Vibration.

Quote:

Originally Posted by DicKy (Post 5534113)

Natural Harrier problems, especially one of the 2019 first batch.

Nope, I wouldn't call this a "vibration". At idle or when driving, the vibrations are perfectly normal. In my case, the whole car shakes (probably 4-5 times in a second).

I found this video which closely resembles the shaking I've experienced. Wouldn't conclude it's the same problem with my engine, because I've never got a chance to watch my engine when it shakes:
https://youtu.be/rAOVL3C0dvg?t=158

Quote:

Originally Posted by pkulkarni.2106 (Post 5534128)

Nope, I wouldn't call this a "vibration". At idle or when driving, the vibrations are perfectly normal. In my case, the whole car shakes (probably 4-5 times in a second).

In my friend's case, the Harrier would do it when we come to a stoplight and put it into neutral. It would vibrate violently in a up and down manner, but would go away after 5 seconds or when we put it into gear.

You say the frequency is 4-5Hz, therefore it cannot possibly be the flywheel, injectors or sensors sending wrong signals (frequency would have been higher otherwise)..

Another obvious possibility is engine mounts. Especially the top engine mount, which is likely damaged and/or has play.

Have all engine mount bolts tightened once at an FNG, to begin with.

Can you also specify the exact engine RPM at which this happens?

I had experienced something identical in a cab (xylo) I was travelling in. When I asked the driver if it was the mounts, he admitted that it was (and though it had been diagnosed, he did not have the resources to get it fixed :Frustrati ).

Quote:

Originally Posted by DicKy (Post 5534286)

Now that observation closely matches with mine. In one occurrence, the shaking went away after I depressed & released the clutch. May be, just may be, it could be because of the slight RPM increase when we lift the clutch.

Quote:

Originally Posted by ashivas89 (Post 5534321)

Another obvious possibility is engine mounts. Especially the top engine mount, which is likely damaged and/or has play.

Have all engine mount bolts tightened once at an FNG, to begin with.

Sure, I'm anyways planning to get a couple of issues fixed at the end of the month. Will ask the mechanic to look at the mounts :thumbs up. One question though - if it were the engine mounts, wouldn't it vibrate/shake too often?

Quote:

Can you also specify the exact engine RPM at which this happens

Unfortunately I don't recall precisely, but it was somewhere near 700-800ish (the usual idle RPM lol:).
Also, I recall for sure that the RPM needle doesn't show any variation when the car shakes.

Quote:

Originally Posted by pkulkarni.2106 (Post 5534330)

Will ask the mechanic to look at the mounts :thumbs up. One question though - if it were the engine mounts, wouldn't it vibrate/shake too often?

Unfortunately I don't recall precisely, but it was somewhere near 700-800ish (the usual idle RPM lol:).
Also, I recall for sure that the RPM needle doesn't show any variation when the car shakes.

The issue might be hard to reproduce possibly because the excitation conditions are not met at all times.

For example, the conditions could be (but not limited to):
1. A specific engine speed (RPM) and the associated excitation frequency
2. The right tension in the mounts (when hitting potholes, speed breakers or aggressive rumble strips, a damaged mount will have movement and the stiffness varies as a result)
3. Stuff that makes 1 vary, like aircon, clutch in/out, cold or warm engine etc..
4. Is the engine bay warm/ cold (heat affects bushing stiffness)

It appears to be an intermittent problem and one that does not occur very frequently. Which means you can more or less rule out all usual “vibration suspects” such as engine mounts, injectors etc. They would rarely cause an intermittent problem.

I would check with an engine/manufacturer specific OB d analyser to see if you have any stored codes.

I would suspect some sort of electrical fault caused by a poor connector or similar.

If there are no codes this is what I would do. Warm up the engine properly, let it idle. Then start pushing and pulling at everything. Start with the whole engine. See if the RPM changes at all if you push or pull it any specific direction. Next push and pull every electrical connection you see. Just tug gently. Observe the RPMs. Next every sensor on the car.

You might be able to find a specific component that causes the engine to shudder and or vibrate

Good luck

Jeroen

Vibrations on a diesel are pretty common, but a judder is something sinister.

1. Mild judders are normal sometimes when turning on or turning off the engine.
2. Mild harshness depending on the condition of the engine, engine oil is pretty much normal.
3. Judders during normal cruising or idling, or judders coupled with rattling, tinging sounds aren't normal. Judders arise due to misfiring, worn out engine mount/beds, faulty/failing clutch assembly, especially during driving and also worn out suspension parts where they tend to make the vehicle wobble either during acceleration or deceleration when there is heavy load transfer.

Since you've iterated this issue being pronounced more at deceleration, and a gentle dab on the acc pedal causes it to behave well, it could be mechanical or electrical. It's better you try to record a video and perhaps show it to the SVC so that they get a better grasp of what's happening.

Good luck though!

Cheers!
VJ