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Matt, Mechanical Engineer
Category: UK Car
Satisfied Customers: 20383
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Sharan starts vibrating when pressing the accelerator after

Customer Question

Sharan starts vibrating when pressing the accelerator after one hours driving when travelling above 60 miles per hour. This makes in undrivable on a motorway for long distances
JA: Will the headlights turn on? Is the battery fully charged?
Customer: yes
JA: What is the model/year of your VW?
Customer: are you a robot?
JA: I'm an assistant to the VW Mechanic. I work with them to help customers like you.
Customer: year is 2006
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: No, I am not hoping to fix it myself but ha
JA: Anything else you think the mechanic should know?
Customer: NO
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the VW Mechanic about your situation and then connect you two.
Submitted: 4 months ago.
Category: UK Car
Customer: replied 4 months ago.
The car only vibrates when traveling above 80KM/H and the accelerator is being pressed
This happens after approx one and half hours driving from cold.
Expert:  Matt replied 4 months ago.


I'd start by checking for worn mountings - check the tightness of the engine and gearbox mounts and their condition - this is best done by using a jack to take the weight of the engine off the mounts and seeing if any cracks or splits open up in the rubber.Also check the tightness of the mounts bolts

and if the car is the 4wd model then I'd suspect that the propshaft either has a worn joint or the centre bearing is worn or its out of balance

you can easily check for for any slack in the propshaft joints by twisting either half by hand and feeling for any play as there should be virtually none

the centre bearing is quite loosely mounted so this can be moved normally but if you can run the car in gear with the wheels off the ground and then feel the centre bearing housing for vibration if there's any then consider replacing the unit

and then look along the propshaft for any signs of a missing balance weight as these take the form of little 3/4" squares that are welded onto the shaft - as they are only tacked on they can sometimes come loose and be lost resulting in the shaft being out of balance - if a joint is worn this can also shake them loose

so if a joint is replaced its good practice to have the shaft re-balanced afterwards

Expert:  Matt replied 4 months ago.


do you still need help?

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Customer: replied 4 months ago.
Hi Matt,
The issue is still not resolved. The mechanic went through your suggestions but found nothing. He did say the exhaust was loose and fixed it. It may be a factor, he suggested this but I find that hard to believe. I will take it for a test drive in the next week- it needs to be over two hours > 80km/h- I will let you know how I get on but my assumption is this issue is not yet resolved. Is it a possibility it is an electrical issue?
Expert:  Matt replied 4 months ago.


if the exhaust was loose then it can start rubbing on the car body as it all heats up and expands, so thats quite possible

and yes you're correct in saying an electrical issue is possible as sensors etc can be effected by heat and start to fail once up to full temperature so this could be a wiring issue as things tend to expand when hot and its possible a poor or partial electrical connection is being pushed apart on one of the major sensors so check the connection plug and wiring to the following;

Airflow meter

Crank position sensor

Cam position sensor

O2 sensor

Throttle position sensor

Also worth checking the connections to the fuel pump for the same reason - unplug each in turn and give them a good squirt of switch / contact cleaner - Not WD40

and also unplug and inspect the main power relays and fuses for signs of overheating or corroded terminals - so the ones for the ECU and the fuel pump

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