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Matt
Matt, Mechanical Engineer
Category: Audi
Satisfied Customers: 21615
Experience:  BEng hons Mech engineering, in auto industry 22 years
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auldi a3 1.6 1998 misfiring badly but had someone mess with

Customer Question

auldi a3 1.6 1998 misfiring badly but had someone mess with it a few days ago stopped juddering as much but still misfiring would i need to change the sensor to correct the hole problem had coil pack changed and changed spark plugs this did nothing
Submitted: 4 years ago.
Category: Audi
Expert:  Matt replied 4 years ago.
Hello

are there any check engine or other fault lights on?
Customer: replied 4 years ago.

no lights on dash


 

Expert:  Matt replied 4 years ago.

Hello



I'd check the condition of the injector plugs / connections as this could be a lean misfire if an injector isn't firing properly - the best way to check this is with a 'noid' light

http://www.noidlight.com/

Then check all the connections to the engine sensors one at a time, remove each one and examine for signs of corrosion or damage and a squirt of contact cleaner ( not WD40) will also help.

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.

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