Q: Car misfires even on new plugs.

asked by on

I drive a Jetta 4 2004 1.6 Model .All four cylinders does not burn fuel effectively such that the car jerks on gear 1st and 2nd, but after that it pulls . On cleaning or putting in new plugs the car stops vibrating and idle well. about 10 kms then it starts again to misfire with no power as usual. It gives out a black smoke smelling petrol at the back.The top was done with new valve seals on and new gasket but did not change engine oil and oil filter. Timing checked and found to ok. Coil pack and plug cables checked and found to ok. What could be the problem , please help.
My car has a manual transmission.

It sounds as though your car is running too rich and fouling the spark plugs. There may be a problem with a temp sensor that is telling your controller that the engine is cold even after it warms up, so the fuel mixture does not lean out as it should when the engine warms. There are also other possibilities, such as a bad air flow meter or the fuel pressure being too high. Any of these problem should have stored a code in your engine’s controller. Normally this would cause the check engine light to come on, but maybe that light is out. Your car should be scanned for codes to see is there is anything to point to the problem. If you want professional help with this you can contact Your Mechanic to have a technician come out to your home or office to check out your Volkswagen and let you know what it’s going to take to fix it.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. Car misfires even on new plugs.

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Q: Glow plug

Like the Check Engine Light, the glow plug light on late model diesels can come on to indicate a problem in the engine control system. Even when the light is out, there should be a trouble code stored in the...

Q: Cant get my car out of limp mode or "fail safe mode"

The reason "limp mode" has become "unbypassable" is due to the existing codes. The ECT failure, if it exists, may alone account for that because an engine coolant temperature sensor is essentially a master sensor - the value of which...

Q: it has a misfire when at slow speed

An ignition system problem is one of the most common reasons for an engine to misfire. As the spark plugs, ignition cables, distributor cap and rotor, and ignition coil wear over time, their ability to transfer the needed spark to...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...