Question about 1998 Audi A4
2.6 a4 avant i have changed idle compansator and have new battery when car is in use it starts first time but when i leave it overnight it is reluctant to start plugs new temperature sender ok if i flick key on off it fires but is reluctant to be rev ved it splutters once it is going the car runs like a dream .butterflyes been cleaned as well
I gotta go with emmissionwiz on this one. Your check valve in fuel pump is not holding causing fuel to drain back this is why when you cycle key you are running pump everytime building pressure. install a fuel pressur gauge and you will see the pressure bleed off after a while. replace the pump and will solve problem
Posted on Nov 07, 2008
It is clearly a problem with air-fuel mixture not getting enough amount of air, as you told us, it is like there is not enough choke.
Naturally here things are more complicate than on an old carb car, and the problem can be caused by more than one part.
The ECM is the main car control module (the computer, a code reading on the car computer can return a list of error codes that can help troubleshooting the problem.
Check the Air Filter and the air intake, eventually try to remove temporarily the filter. If the care idle normally without the air filter, then replace the filter. You can also replace the air intake with a bigger one (monster air intakes).
The Air Mass Meter and Mass airflow sensor measure the mass of the air getting into the engine. If there is a problem with this parts, you may experience idling problems
The Oxygen Sensor is used to determine how well the fuel is burnt though the engine combustion operations. Then the electronic fuel system adjust mixture to save fuel. When oxigen sensor is bad you can get a low idle. Here you get a replacement.
If you decide to do it yourself I suggest also buying the Repair Manual , if you haven't done it already.
And do a computer scan as first thing.
Posted on Nov 06, 2008
You may need to get a new fuel pump, fuel filter, starter, or alternator. Try going to a mechanic and see what they say and they should be able to diagnose and fix the problem for you. But it seems as though it may be more than one thing because a faulty alternator will drain a battery and make it start sluggishly, and the fuel pump may not be giving gas fast enough probably because of a clogged fuel filter. So just get it checked at a shop and they should fix it.
Posted on Nov 03, 2008
I greatly recommend that you should also check the Fuel strainer. it could have been blocked. blocked strainers causes hard starting and low engine power or even sudden engine stop.
if your cars was stock for months or even weeks, try to clean also the sparkplug connectors.
check also your car's engine oil, it should not be too thick as this would not circulate properly (thick oil gets even thicker at cold temperature). you could use thin synthetic oil.
Posted on Nov 03, 2008
Cold engines might experience problems at the time to start due to different reasons. One of these reasons can be based on the effect which cold has on liquids evaporation. When it is cold, gasoline evaporates less and this cause it to be more difficult to burn due to the fact that it is burnt when it is evaporated.
Another reason by which a cold engine might have problems to start is caused by the fact that oil becomes much thicker in cold than the way it is in hot. Oil, like any other liquid changes its consistency when it is exposed to very low temperatures as well as it changes back when it is in a very hot weather, and this might cause oil to have problems at the time of circulating in the car engine.
Besides the engine, car batteries might experience problems while being in cold weathers as well and this could affect the engine. Batteries function through chemical reactions which loose agility while being cold and therefore, in such circumstances, batteries don't function properly. When this happens, the car energy becomes affected and this causes problems for the engine start.
If these three problems happen together, starting an engine might become a really hard task to achieve. In order to overcome the lack of gasoline evaporation problem, you can spray ether into the engine which would evaporate quickly and help the engine start. Besides this, you can also to prevent having oil too thick which wouldn't circulate properly by using thin synthetic oils. You should also try to maintain the car isolated from cold as much as possible, but by using the two last mentioned methods you would experience much less problems at the time of staring the car in cold weather.
Posted on Oct 31, 2008
This sounds like the throttle position sensor(TPS) , to test , leave key in forward position, then under the hood unplug the sensor then plug back in , if it starts right up then you need to replace the sensor , could also be idle air control motor(IAC motor) do the same to check it
Posted on Oct 31, 2008
Stalling: Sensors such as the cam and crank
sensors signals if the computer don't see it-it will not fire the coil
and provide injector pulses. And Idle Air Control Valve not targetting
the idle speed and an EGR valve that's cracked open will lean out the
air/fuel mix causing it to stall to include the MAF sensor.
Refusing to start at times could be the coolant temperature sensor is out of range and computer not adjusting fuel as needed during initial cold starts.
Fuel Injection Stalling Problems
On fuel injected engines, stalling can be caused by anything that upsets the air/fuel mixture. This includes vacuum leaks or unmetered air entering the intake manifold downstream of the airflow sensor, a faulty throttle position, MAP or oxygen sensor, dirty fuel injectors, or low fuel pressure to the injectors (weak fuel pump, faulty fuel pressure regulator or restricted fuel filter). Like older carbureted engines, a defective thermostat may be preventing the engine from warming up quickly or reaching normal operating temperature. Or, a defective coolant sensor may be telling the PCM the engine is colder (or warmer) than it really is. Any of these conditions can upset the fuel calibration of the engine and cause a problem.
Idle Speed Control Circuit
One of the most common causes of stalling on fuel injected engines is the idle air control (IAC) solenoid or idle speed control (ISC) motor. If the idle speed control device fails to provide the correct idle speed, the engine may die when you slow down or come to a stop. In many cases, the idle control solenoid or motor is gummed up with carbon and fuel varnish deposits. Cleaning the idle port in the throttle body, and the IAC or ISC valve with aerosol throttle cleaner can often solve the stalling problem. If the situation is not improved after cleaning, however, the IAC solenoid or ISC motor may have to be replaced. Check the connector to the device to make sure the connector is not loose or corroded.
Engine Control Issues
Sometimes stalling is the fault of the Powertrain Control Module (PCM) or the inputs to the PCM. The factory programming may not provide enough idle speed when the A/C is on, when the alternator is under high load or when the temperature is unusually hot or cold. The fix here may be to reflash the PCM with the latest OEM update.
A faulty MAP sensor can sometimes mislead the PCM into thinking the engine is under a greater or lesser load than it actually is. The MAP sensor senses intake vacuum, which the PCM uses to estimate load so it can adjust the air/fuel mixture accordingly. If the MAP sensor isn't reading right, the PCM will receive bad information and possibly add or subtract more fuel than it should causing the engine to stall.
The same thing can happen if the throttle position sensor on a speed/density EFI system (no airflow sensor) is out of calibration or had a dead spot. The PCM may not realize the throttle is at idle, and may give the engine too much or not enough fuel causing it to stall.
When attempting to diagnose an intermittent stalling problem, therefore, it's important to always use a scan tool to first check for any trouble codes that might shed light on the condition, and secondly, to look at all the essential sensor inputs to see if they are within range and are supplying accurate information to the PCM.
Intermittent stalls that seem to happen at random are often ignition-related. A sudden loss of spark will kill the engine cold and prevent it from restarting. The most common causes for loss of spark include hot shorts/opens in ignition coils, ignition modules and crankshaft position sensors. Loose or corroded wiring connectors that cause a sudden loss of voltage in the ignition circuit will also stop an engine dead in its tracks
Posted on Oct 31, 2008
You may want to try a can/bottle of injector cleaner in the fuel tank.Do you live in a high humidity area as moisture can cause this until the engine heat heats it off.
Posted on Oct 31, 2008
This problem is caused by the failure of the check valve in the fuel pump, after the car sets the fuel drains back to the tank and it will take repeated tries to fill the lines and fuel rail at the engine to supply the injectors, the sputtering is caused by the air in the line, like a garden hose when it is first turned on, once the air bleeds out of the lines the engine smooths out, have seen this same issue dozens of times in my 20 years as a new car dealership technician, all I did was these kinds of problems, my specialty was automotive electronics.
Posted on Nov 05, 2008
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