Question about 1998 Volkswagen Jetta
Idle haunting is mostly caused by a bad 02 sensor, there are mostly 2 sensors. If one goes bad the other will try to compensate for correct mixture. You can also check the Engine temp sensor, malfunction of the sensor can also falsely produce a rich or lean mixture. The throttle adaptation also need to be learned each time power is disconnected from the ECU. It's simple to do but a VAG scan tool or equivalent is needed to access the throttle body controller under 04 basic setting.
Posted on Feb 10, 2015
The fuel pressure regulator is on the fuel rail. With the pressure you have it is not the regulator. The heater circuit code is probably for the temp sensor. I would replace the temp sensor first. It is cheap, just make sure you replace the "o" ring. Bleeding the coolant system is a pain you just have to keep filling the system up with the expansion tank cap off till the cooling fans run. let it cool down and top off. The second thing I would do is have the dealer set the throttle body basic settings. They will charge you an hour to do it, but only they can do it. If none of that helps you have a bad mass air flow meeter. They give a false reading for air flow and the fuel system is delivering to much fuel because of it. Hope this has helped.
Posted on Dec 09, 2014
If pinching the fuel return line gives an improvement that there is not enough pressure at the injectors. This points to a fuel pressure regulator problem. Some are vacuum controlled so check that area first. Others may be electronic controlled so run fault codes to see if a fault has been recorded.
Posted on Dec 09, 2014
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Posted on Jan 02, 2017
SOURCE: 99 olds alero 2.4
I'm sure you have installed a fuel pressure gauge and monitored the fuel pressure while the problem is occurring?Another diagnostic tool which is easy to do,is while the problem is occurring,unplug one sensor at a time beginning with the Mass Air Flow first,.if it uses one.Many times,not always,depending on the sensor,if the sensor is taken out of the picture as far as what the PCM is seeing,like unplugging the MAF,the PCM will substitute the missing sensor output with a generic value that will allow the engine to at least run,and if unplugging for example the MAF,the engine idle speed returns to normal,you know you're onto the problem.You didn't mention if the engine ran ok other than the idle problem.As far as checking for vacuum leaks,i use something like brake cleaner or WD 40,more of a liquid,and it does sound like a vacuum leak.Plastic intake manifolds do develop nearly invisible cracks that open up more with heat.Revsisit the possibility.And as for the PCM,it is possible,but more likely a mechanical problem.Lastly,remove an O2 sensor or two before the catalytic convertor,run the engine and see if anything changes.Cheap way to verify the catalytic convertor is flowing and not restricting engine airflow,as i have seen bad cats cause misfire codes and strange problems.Good luck.
Posted on Dec 04, 2008
most likely idle air control sensor or low engine coolant I know sounds funny but IAC uses coolant to regulate idle. Idle air control valve or throttle body positioning sensor.
Posted on Feb 26, 2009
ok i have the same truck my timing was off 3 teeth but mine wouldn't kick out of high idle is y mine was surging but know with timing right no vacuum leaks i cant get it below 1400 but when a vacuum turns on it almost kills my engine any thoughts i know i got a vacuum line mixed up idk were though
Posted on Jan 19, 2010
Fuel injectors go bad on these engines, you can find re manned ones for 30 bucks. If you have an engine light on get that read. Change your coil/wires/plugs also. Is the lower intake manifold gasket leaking coolant yet? You may want to get that replaced also. Check the TPS too (throttle positioning sensor) those will also cause your engine to act up
Posted on May 08, 2010
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