Question about 1998 Volkswagen Jetta

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I have a 98 jetta gls abs after it warms up it idles rough like rocking bacj and forth. When i pinch the fuel return line it gets better and the fuel pressure is at 30 psi. I work at goodyear and can't figure it out. I have a evap code a heater circuit code and a rich code

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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

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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

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  • Volkswagen Master
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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

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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

  • 5 Answers

SOURCE: Where is the fuel pressure regulator located on an 2002 f150 v6?

in the center of the motor,in the rear on the fuel rail

Posted on Jan 19, 2009

godspeed808
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SOURCE: olds alero 2.4 idle fuel pressure

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

  • 1 Answer

SOURCE: 1997 Nissan Hardbody has rough idle/surges/stalls

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

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SOURCE: 97 buick lesabre 3.8 Idles rough and stalls out.

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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1 Answer

2001 Mercury Sable - already asked but this is in better detail???


Not plugs. Go to AutoZone, Advance, or Oreilys autoparts for a FREE scan. Bring pen and paper and write down trouble Code that their scanner shows. Clerk should be able to tell you, but you want the Code so your can price repair.
Once you get Codes you can call and price work. A few can be done without much effort. Unfortunately the ABS may be a victim of heavy braking. The ABS can be checked with a better scanner(Not all are equal).
Try tightening the gascap, although each time you added fuel additives you did that, know that one Code may be related to a loose cap.
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When warm my 99 camaro v6 runs like ****. I can't


Well, the first thing I would ask is what codes are you getting from the computer? If it is running that bad, your check engine light has got to be SCREAMING at you.

Then, you sort-of answered the question for me by stating that the fuel pressure is at 38 psi. The fuel pressure specification for a 1999 Chevrolet Camaro equipped with a 3.8L V-6 engine is 48-55 psi. I'll bet you have lean oxygen sensor codes and a random misfire code. (they'll do that when the fuel pressure is low.)

I would first try replacing the fuel filter and see if the numbers don't come up.
If that does not work, block the fuel return line and see if the numbers get better. If they do, you have a bad fuel pressure regulator. If they don't you either have a restriction in the fuel line or a bad fuel pump.

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get a pair of pointy nose pliers start the car let the engine revs settle, when they have pinch off the return line from the fuel rail and see if the revs come up if so you have a injector problem and get the m cleaned (don't pinch off the hose to long as it will make a fuel leak only do it for a couple of seconds)

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Do you have any rough idling or anything? Is the check engine light on?

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Olds alero 2.4 idle fuel pressure


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