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Injection Troubleshooting

Fuel system problems can be very difficult to explain because electrical problems can cause fuel components not to work correctly. We generally assume the electrical system is OK and we don’t go down that road.

Engine hesitates when stepping on the gas

This can be caused by several things which I list here not in any order. The best thing to start with is check for trouble codes using an ODB tester.

  • Dirty fuel filter
  • Dirty air filter
  • Bad Throttle Position Sensor – TPS
    • Measures where the accelerator is and works and communicates this with the computer, which adjusts timing and fuel.
  • Dirty fuel injectors
  • Bad oxygen sensor – O2
  • Catalytic converter
  • Bad ignition coil
  • Leaky or clogged EGR valve
    • Check to see if there is carbon build up.
  • Bad air float sensor – MAF
    • The MAF measures the amount of air entering the engine and sends this to the computer. A bad MAF can result in hesitation, bog, or stumbling. This may not register a trouble code.

What Causes Rough Idle

Common symptoms: Loud engine, RPMs fluctuating, Purring noise, slow acceleration.

Using the process of elimination, start with the most common and if not found continue down the list to figure out the problem.

Most common causes:

Other causes:

  • O2 (oxygen sensor)
  • Dirty air filter
  • EGR valve (exhaust gas recirculation)
  • MAF sensor (mass air flow)
  • ECT Sensor (engine coolant temperature)
  • PCV Valve
  • IAC Valve (idle air control)
  • Throttle valve
  • Fuel pump
  • EEC (evaporative emission control) sometimes knows as EVAP or ECS
  • Head gasket (not common)

Smoke Coming Out of the Exhaust

Smoke from exhaust.

Types of Fumes from exhaust.

White Smoke- Thick white smoke can be caused by the engine burning coolant. When this happens, run your car to the shop ASAP.

Black Smoke- If you see black smoke that means that your engine is burning too much fuel, or its not burning all the fuel. (Caused by dirty fuel injectors, damaged sensor, fuel pressure regulator.)

Blue Smoke- An indication that the car is burning engine oil. This happens when the piston rings are worn out and oil is leaking to the combustion chamber where it is burned together with the fuel.

Grey Smoke- This kind of smoke can be due to the car burning oil or a bad turbo charger. It can also be due to automatic transmission fluid getting burned up in the engine.

A perfectly tuned car should have colorless emission, if you see it emitting smoke in the colors highlighted above. It’s time to replace something. (Do it yourself or pay someone else.

My 2000 Ford Expedition has rough idle and dies at stops. The rpm starts dancing wildly. Told it could be fuel pump, I think it’s injectors.

At idle and slowing down the rpms start dancing around

  • Possibly dirty air filter.
  • Bad alternator – Start the engine and disconnect the battery terminal. If the engine dies then the alternator is not putting out enough juice. If it doesn’t die and continues to idle and jumping Rpms then it might be the “solenoid” that’s connecting that to the spark plugs
  • Replace spark plugs if old.
  • Replace fuel pump if old.

Updated on 07/17/2021

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