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Matt
Matt, Mechanical Engineer
Category: UK Car
Satisfied Customers: 16596
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Car sounds like its going to stall,revs and shakes..petrol

Resolved Question:

car sounds like it's going to stall,revs and shakes really badly,mostly uphill,this only started after we put petrol in yesterday
Submitted: 4 years ago.
Category: UK Car
Expert:  Matt replied 4 years ago.
Hello

Its possible that the fuel you recently added was a bit stale, this is something to watch if you've bought from a garage that doesn't have a lot of custom.

Or this could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and leans the engine out causing rough running. Also as it’s a mechanical fault it usually won’t turn on the check engine light.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas around each joint in turn. If the engine rev's up you've found your leak.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine

Might also be worth cleaning out the idle speed control motor / valve as these get clogged up with carbon and some brake cleaner washed through helps free things off.

Customer: replied 4 years ago.
Hi Matt,if its air in the petrol tank ,which probably sounds like it,what can i do,or will it correct itself
Customer: replied 4 years ago.
sorry,last question,could this happen if the petrol tank is to full?
Expert:  Matt replied 4 years ago.
Hello

It won't be anything to do with air in tank as there's always some air in the tank.

It could be the fuel you bought is stale in which case try topping up with some fresh fuel from a garage which is busy and hence will have a high turnover of fuel.

The tank cannot be too full providing the breather system for the tank is working OK, to check if it is simply remove the filler cap and try running the engine if this sorts it out then there's a problem with the tank breather system.
Matt, Mechanical Engineer
Category: UK Car
Satisfied Customers: 16596
Experience: BEng hons Mech engineering, in auto industry 22 years
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