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    Thread: 2000 Jetta vr6 running horribly rich

    1. 05-22-2018 08:49 AM #1
      New project, already verified that the timing is spot on, new cam and crank sensors, brand new ngk plugs, good compression and leak test on heads. No misfires in live data. Something is causing it to run so rich you can smell the fuel at idle and the throttle response is horrible because of it. Looking on what it could be besides o2 sensors, It’s got the green coolant sensor

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    3. Member
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      05-22-2018 10:39 AM #2
      Your MAF sensor could be faulty.
      Kenji

    4. 05-22-2018 11:38 AM #3
      I forgot to mention that it has a new maf, and when you disconnect it the car dies, so I know it’s working

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    6. Member
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      05-22-2018 02:22 PM #4
      Actually, when you disconnect the MAF sensor, the ECU uses a default set of fuel maps, so the engine should not die. In fact, people with bad MAF sensors often find that the engine runs better with the MAF sensor disconnected.

      So your engine should not die when you disconnect the MAF sensor. This doesn't directly address your issue, but it is an interesting data point.
      Kenji

    7. Member b5in's Avatar
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      05-23-2018 11:06 AM #5
      Sounds a lot like how my 2001 VR6 was running. I replaced the spark plug wires and noticed the air box to throttlebody boot wasn't on all the way. Not sure which of the two fixed the problem but I would double check to see if there's a intake leak somewhere after the MAF. Weird thing is my car stalls out as well when I unplug my MAF (which I recently replaced so I know it's good)
      I DUB 4 FUN B!TCHES

    8. 05-25-2018 01:08 PM #6
      Update: so I was mistaken with saying the car dies when I disconnect the maf sensor, it runs with no noticeable change, it’s when I plug the sensor back in while it’s still running after it’s been disconnected that it dies, which I believe is normal. Anyway I picked up an oe Bosch maf and swapped it in and there was no difference, and in live data both sensors performed the same. After I was done checking the data I decided to check the cat since it was getting dark and lo and behold it was cherry red. So either the cat is plugged and it’s whats causing my issues ( throttle delay with no load, runs rough, running rich, horrible power loss under load, high rpms and under powered) or the rich condition is just feeding the cat extra fuel and it’s making my cat not happy. Either way I’m going to replace the cat. So I guess I have further test to do before then. I’ll check fuel pressure at the rail to see if my fpr is jammed closed, I don’t have a blown diaphragm so ( no fuel blowing out the vacuum nipple) so I’m guessing it may be stuck. I’ve got a new coolant temp sensor and o2 sensors so I may as well install them. When I pull the o2 sensors I’ll start the car to see if it runs any better, at least I’ll know if it’s just a plugged cat at that point. Also I found a small vacuum leak at the small hose that plugs into the bigger line off the oil fill reservoir. It’s almost like those hoses are collapsing due to vacuum, so tomorrow I’ll head to the junkyard where there’s a nice mk4 vr6 Jetta like mine and rob that breather hose assembly, fpr, plug wires, and coil from, I’ll eveuntually need a new wiper motor and both front window regulators but I’ll worry about those once I get the engine issue worked out. As always any input you guys have is always appreciated. I’m a mechanic but I’m new to vw’s and it’s always a pain to learn a new platform from scratch


    9. 07-19-2018 04:32 PM #8
      Just looking for some input on the running condition of the car, I’m currently re checking the timing, this video is just me trying to check my mounts for play, I’ve got the autotech camplate coming in a few days from ecs tuning, when I first checked timing I used some homemade plates, so I’m worried maybe it was half a tooth off, I’m at my wits end if it’s not the timing. It’s got new plugs, wires and coil pack, maf, cts, radiator. I checked the cat and it’s perfect, o2 sensors are good. Last time I let it run for a while and the cat was glowing, it smells like fuel. Compression check across all cylinders was 150, fuel pressure was also within spec.

    10. Member fopeano's Avatar
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      08-18-2018 06:40 AM #9
      I'm dealing with a supercharged s2000 at work that runs ok but absolutely reeks of fuel at all times it's running. It turned out that the one of the fuel injectors was stuck open. Found that by pulling the fuel rail with all injectors attached and operating the fuel pump. With pressure in the rail, #3 sprayed continuously even without the wiring being plugged in. It spraying when unplugged confirmed that it was a mechanical problem. If it needed to be plugged in to stick on, that would have indicated a short to ground in the wiring or a failed injector driver within the ECU.
      I used my 6 years of Mk2 hobbyist training to become an auto tech in 2005, but that makes you not want to work on your car as much. I'm also a VR6 noob in 2018.
      YouTube channel of my cars, blown up cars from work, and some of the more interesting work I've done

    11. 06-01-2019 07:05 PM #10
      Did you ever find out what was causing these issues? Im going through something very similar with a VR6 12v wagon right now and so far, the two threads i have going are getting any results..

    12. Senior Member reynolds9000's Avatar
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      06-02-2019 08:25 AM #11
      Assuming you're having all the same symptoms as the OP, it is almost definitely a bad MAF sensor. If you have the engine running when you unplug the MAF and it stalls out when you plug it back in, the sensor is bad.
      1995 Jetta GLX - Candy White
      1997 Jetta GL - Sequoia Green - 12v VR6 - Vortech V2

    13. 06-03-2019 03:02 PM #12
      Quote Originally Posted by reynolds9000 View Post
      Assuming you're having all the same symptoms as the OP, it is almost definitely a bad MAF sensor. If you have the engine running when you unplug the MAF and it stalls out when you plug it back in, the sensor is bad.
      Thanks for the advice on that one. I figured that since I had just replaced it, it was ruled out as a culprit. Sure enough, I unplugged it and the car stumbled for a second but continued to run. Plugged it back in and it died. Cleaned the original sensor that I still had laying around and plugged it in. Started the car and it stumbled when I unplugged it, just as the replacement on had done. Plugged it back in and the car kept running like it hadn't even noticed that I plugged it back in. I guess that Assumes that the original one was never bad, to begin with. Odd thing is, it seems to idle better with less hunting and surging issues with the "bad" one installed rather than the original "good" one installed.

      I pulled the original one back out just to measure it and per the Bently Manual, page 24c-13 I was getting the correct ohm readings between pins 1 & 3 per the chart. I also verified that with heat on the sensor, it went down and with cool air, it went up in resistance, therefore the IAT sensor portion of it is working.

      I also have another thread going so I won't clog up the OPs thread and will post this info there.

      https://forums.vwvortex.com/showthre...#post113407217

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