# Running problem with '98 Beetle 2.0



## sp1249 (Feb 2, 2005)

I have a running problem with a '98 Beetle 2.0 AEG engine that has me baffled. It came to my shop with a check engine light indicating a misfire on all 4 cylinders. The car starts up, runs good and accelerates fine for the first 20 seconds and then will just bog out when the throttle is applied. It never stalls, it will just go back to normal idling without misfiring. Whenever any kind of throttle is applied above idle, it just falls on it's face, along with misfiring. If it is warmed up, it is just barely driveable, but is very sluggish and misfires. If you feather the throttle, it can eventually get to 55 mph. The same "misfire on #1, #2, #3 and #4 cylinders" codes shows up after it has been cleared. As I said before, during the first 20 seconds after a cold startup it idles and revs up normal but after 20 seconds of running normal it will fall on it's face if any throttle is applied. 
Here is what I have done so far:

*removed the upstream 02 sensor to see if I had a plugged cat.
*installed new plugs and plug wires (which it needed)
*installed new temp. sensor
*tried 2 different air mass sensors
*tried 2 different coil packs
*added can of Seafoam fuel injector cleaner
*checked timing belt reference marks
*tried different throttle body
*installed new fuel pump with new filter
*checked all the fuses related to ECU and engine management
*tried different ECU
My next step will be to check the ECU electrical connector for power, grounds and continuity between engine components.
If anybody can shed some light for me as to what is going on here, it would be deeply appreciated.
Thanks in advance.


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## racechaser (Oct 28, 2008)

*Re: Running problem with '98 Beetle 2.0 (sp1249)*

I don't see MAF listed, you might try unhooking it & see if it runs better. You might unhook the temp. sensor after it is started & see if it will run better. I had a 92 cabrio that it would not pull up to speed & leaving black exhaust spot on driveway, unhook temp sensor & it ran good.


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## sp1249 (Feb 2, 2005)

I did try the to run it with the temp. sensor disconnected and also tried running it with the mass air sensor disconnected---both had the same results---still has the same running problem. Nevertheless, I appreciate the advice.


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## sp1249 (Feb 2, 2005)

I haven't had the chance to test the wiring at the ECU connector yet, but I did completely remove the cat. converter to rule out a plugged cat and still have the same running problem. Also replaced the fuel pressure regulator and that did not change anything. I inspected the plastic fuel lines under the car and they look to be fine. I am out of ideas as to what the probem is with this car. The only codes that show up is misfire on all 4 cylinders. I know it isn't much, but I'll pay $50 to the person who gives me the correct diagnosis on this car's running problem.


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## digraph (Jul 23, 1999)

*Re: Running problem with '98 Beetle 2.0 (sp1249)*

Did you check the vacuum lines, especially the one between the intake manifold and the fuel pressure regulator?


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## sp1249 (Feb 2, 2005)

Checked the vacuum lines---they are good.
Thanks


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## v4hrc (Feb 9, 2009)

*Re: (sp1249)*

Have you checked or replaced the o2 sensors? MY Beetle is doing the EXACT same thing, and I've checked all the same stuff with no results. I'm getting decent fuel pressure (40-45psi while running) but the car still runs like crap. No codes other than the misfires. The car DOES run better when I have the fuel return line pinched off to raise pressure, but it's still not right. 
Could the o2 sensors be causing this?


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## sp1249 (Feb 2, 2005)

I also just discovered today that when the return line is pinched off, the car runs fine. Last week, I did remove the converter to confirm that I did not have a plugged cat. Both oxygen sensors are located in the header / converter pipe assembly and all I got was oxygen sensor codes because they were disconnected. The running problem was still there. Bolted everything back together, cleared the oxygen sensor codes but still have the misfire codes. I don't think this is anything oxygen sensor related.
I am not seeing any damage to either of the fuel lines. Checked the fuel pressures and got pretty much the same pressures that you have, which are within specifications.(It does has a new fuel pump assembly) Tried another fuel pressure regulator but nothing changed with the running problem. As I said before, when the return line is pinched off, the car runs fine and it revs up as it is supposed to when throttle is applied. When the return fuel line is unclamped, it goes back to falling on it's face when throttle is applied.
I'm still in the dark on this problem.


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## v4hrc (Feb 9, 2009)

*Re: (sp1249)*

I ordered some o2 sensors last night, hopefully they'll be here Thursday. I'll post results. They look like they've never been replaced, and ours has 140k miles on it.


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## v4hrc (Feb 9, 2009)

*Re: (v4hrc)*

well, the O2 sensors didn't help so I'm still looking for answers. I'm going to probably drop by the local dealer tomorrow and see what diagnosis costs...


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## sp1249 (Feb 2, 2005)

Still have got nothing resolved with my car's problem. Still wondering why the car runs better with fuel return line pinched off. 
Please keep us posted on what you find out with your car.


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## elRey (May 15, 2001)

*Re: Running problem with '98 Beetle 2.0 (sp1249)*

Did you preform TB adaption procedure?
Are the injectors the correct ones? (air shroud with air hose to each one and intake)
A good vac signal to fpr
an AEG coil (waste spark) v.s. an AZG+ coil (sequential)


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## sp1249 (Feb 2, 2005)

Did you preform TB adaption procedure?
***Yes***
Are the injectors the correct ones? (air shroud with air hose to each one and intake)
***Yes***
A good vac signal to fpr
***Yes***

an AEG coil (waste spark) v.s. an AZG+ coil (sequential)
***Yes***


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## Jay-Bee (Sep 22, 2007)

*FV-QR*

What plugs are you running?


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## sp1249 (Feb 2, 2005)

I'm running the NGK's that a '98 Beetle with a 2.0 AEG came stock with from the factory.


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## jamesr88 (Oct 9, 2007)

did you do a compression test???????????


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## sp1249 (Feb 2, 2005)

Compression is fine.


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## twicepardoned (May 2, 2006)

Did you pressure the system with air to find a vacuum leak? (I prefer this method because it is quieter than testing with car running)


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## sp1249 (Feb 2, 2005)

I realize that the hoses for the power brake booster and the fuel pressure regulator can be clamped off, but how can air pressure be applied without leaking by the throttle plate and intake valves?


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## v4hrc (Feb 9, 2009)

*Re: (sp1249)*

PROBLEM SOLVED.
I'm not sure if this is the same situation with yours, but at least it's food for thought. The dealer I took it to found issues with the MAF sensor, but they were also getting intermittent/inconsistent readings. They suggested replacing the connector on the vehicle side. They even had the parts in stock. I also got a new MAF sensor (not from the dealer though, too much $$$). They sell a replacement plug, and also wires with the "sockets" already crimped on. And they're looped with two per wire, so you only need to buy three. 
After cutting off the old plug, I removed the sockets from the plug and found the 12v lead (blue/yellow) was definitely splayed open. The other ones were also weak, but not as bad. With a little bit of soldering and heat shrink tubing, I put the new socket together and also wrapped the outside of the wiring sheath with another layer of spiral wrap wiring protector, the solder joints wouldn't tuck inside very neatly. New MAF and plug installed, and now the car runs better than it ever has. But then again, we've also replaced a lot of parts








The part numbers are...
1J0-973-775-A Housing $6.88 local price
000-919-133-A Wires $5.91 local price
Here's a few pictures of the repair:
http://www.rc30.us/vw1.jpg
http://www.rc30.us/vw2.jpg
http://www.rc30.us/vw3.jpg
http://www.rc30.us/vw4.jpg
http://www.rc30.us/vw5.jpg
Hope this helps!!


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## sp1249 (Feb 2, 2005)

I tried a new connector for my mass air sensor and that did not change a thing for my running problem. I thought that would have done it seeing I've replaced every component on the engine. My $50 offer still stands for the correct diagnosis on my running problem.


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## JustTheTip (Jan 22, 2008)

1)have you checked voltage at the fuel pump?
2)have you check the fuel pumps ground?
3)when you say that u checked fuel pressure did you test at idle or while the "bogging" is occurring?
It sounds like the fuel pump is running on a lower voltage than needed(which would make it run at a lower speed) If the pumps is running at a lower speed it will have sufficient fuel pressure/volume at idle and low pressure/volume at higher rpm's when the demand on the fuel pump is higher.


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