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    VWVortex


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    Thread: 99 Passat : Intermittent no start

    1. 03-24-2010 01:41 PM #1
      99 Passat 1.8t, AEB, tip

      I have been having this problem for awhile now. Some days it starts right up, others it just cranks and cranks but doesnt fire, and then others it starts but then runs really rough like its misfiring, until it eventually clears and then runs normal. It seems to be worse the longer the car sits, but once it starts for the first time of the day its almost always fine the rest of the day. Although i will still get slightly rough starts where it misses a few times but then smooths right out.

      I have vag-com, and the only dtc's im getting are for random intermittent misfires in cylinders 2 and 3. I have had issues with misfires before, and its ALWAYS been in 2 and 3. It definitely feels like im not getting fuel or not getting a spark. I have a feeling that its an electrical issue, either a faulty sensor or bad ground or relay or something....?

      I have checked (only visually) the grounds that i know where they are, all seem to be intact...

      I have done quite a few things to this car, and all of these have been done since i have had this problem...

      -new o2 sensor
      -new fuel injectors
      -cleaned the MAF
      -new intake air sensor
      -new coolant temp sensor
      -new plugs
      -new ICM
      -new coilpacks
      -swapped in a different ECU

      im sure there are other things too, but those are the most recent and the ones i can remember off the top of my head

      I was ALMOST convinced it was cold weather related, but then yesterday and today i had the same issues. Its not hot here in cny by any means, but it has definitely been warmer. Since the nicer weather broke a couple of weeks ago it has been great, up until yesterday and today.

      Anyway, does anybody have any input or guidance??? I have already thrown alot of parts at this thing, but i considered most of them to be good maintenance items. I dont really want to keep throwing random things at it though. So i would love to hear from people the have had similar issues, or any good educated guesses!!!


    2. Member vwfansince95's Avatar
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      03-24-2010 06:44 PM #2
      here are a few thoughts for you; fuel pump, fuel filter or maybe even fuel quality

      and after thinking about it, quite possible that you might have a bad cell in the battery too -


    3. 03-24-2010 11:55 PM #3
      the fuel filter was changed under 2000 miles ago. The battery is new (8 months or so) and vag-com always shows it at the proper voltage. I dont think poor fuel quality is the issue...it may cause the car to run rough, but just crank with out firing? That doesnt seem very likely to me.

      The fuel pump is definitely something i have wondered about though. When i changed the injectors i pulled the fuel pump fuse and cranked the car over several times to depressurize things, and thats exactly how the car acts when it wont start....it just cranks but doesnt fire.

      Is there any way to test the fuel pump? That is a job i would definitely want to know for sure that it NEEDED to be done before i just threw a new part at it.

      These damn intermittent problems are so hard to diagnose! I can replace the pump and not know if i fixed the problem or not. I just have to wait and see if the hard start/no start issue comes back. All winter i had this problem. Some times i would go weeks with no issues, and other times it was every other day.


    4. 03-25-2010 03:05 PM #4
      well the fuel pump seems to be working fine. I removed the access cover and had somebody turn the key for me and i can definitely hear and feel the the pump working. I wanted to test the voltage at the pump and the fuel level sending unit, but i couldnt get the wiring harness disconnected for the life of me.

      I may depressurize the system and pull the fuel feed line off the fuel rail and see and make sure i have flow there. I dont have a way to check fuel pressure properly at the moment.

      I guess my next step is to check for spark. Im pretty confident the ICM is fine, as its only a couple of months old, although i guess i should/could check it to be sure (multimeter). Is there any other way to check for spark? Can i pull the coil packs out and check?

      I am wondering if it could be the cam postion sensor maybe? Its about the only other sensor i havnt replaced, besides the knock sensors. I have read that a faulty cam position sensor can cause no start issues...

      Any other comments or ideas???


    5. 03-25-2010 03:20 PM #5
      I know exactly what you're talking about. I have a Jetta 1.8t and my car does the same thing, however I've been told it is because I have a blow off valve. Apparently our cars hate those things. My buddy with the same exact car had never seen this before, he put a bov on his car and he immediately started experiencing the same thing. I had so many people tell me it was that, I just believed it. That's my 2 cents, good luck with your search! If you find out what it actually is, shoot it my way, because I would love to know if it's something besides the bov!


      Modified by Tesonator at 12:22 PM 3-25-2010
      2001 Red Jetta Wolfsberg 1.8T, APR 93 Stage 1 Tune, ECS Stage 1 Coils, Neuspeed P-Flo Intake, Forge BOV, Straight Pipe Exhaust, and a stereo that will RIP YOUR FACE OFF!

    6. 03-25-2010 03:50 PM #6
      I dont have a BOV. I have upgraded to the TT diverter valve, but its still a diverter valve.

      The reason a BOV is bad for our cars is because the ECU thinks the extra charge air not being used being diverted, not BLOW OFF is being put back into the intake system. So it calculates that air being there, when it isnt...the car runs like crap. But i dont believe it would cause the issues you are having, although i most definitely could be wrong! I am almost positive its something electrical, not mechanical.

      When ever i find the answer to this i will definitely post it up. I hate reading threads that seem like they will be really helpful, but then the OP doesnt post the final result...


    7. Member vwfansince95's Avatar
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      03-25-2010 05:13 PM #7
      Quote, originally posted by VisionQuest78 »
      I am wondering if it could be the cam postion sensor maybe?

      x2- that woulda been my next guess. you might also wana check into the Fuel Pump Relay, Immobilizer, MAF replacement.


    8. 03-25-2010 05:36 PM #8
      correct me if im wrong, but wouldnt i not hear and feel the fuel pump working if the relay was bad? If the relay was bad, wouldnt the fuel pump just not work at all?

      The 99 AEB doesnt have an immobilizer.

      MAF is one i have considered also. That was why i cleaned it awhile back. I guess i could try unplugging it and see it starts...

      For the cam position sensor, is anybody aware of a test that can be run to check if it is working properly, like using an ohm meter or something? I was looking through my haynes manual, and it says the timing belt and sprocket have to come off to change this....is this really necessary??? That is way more involved than i want to get, unless i know for 100% certainty that it is bad!

      The engine speed sensor is another possible culprit. That and the cam position sensor are heavily tied in with ignition timing... so if im going on the educated guess that lack of fuel isnt the issue, and that its lack of spark....?

      It has been over 2 days since the car has started, and in the months and months of dealing with this that has never happened. Its ALWAYS started eventually. So maybe its not an intermittent problem any more. Which in an odd way, i am actually grateful for! Will make it easier to diagnose, or at the very least i will see instant results after replacing whatever the faulty part is, instead of just waiting and wondering if it will not start again.


    9. Member vwfansince95's Avatar
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      03-25-2010 05:46 PM #9
      Quote, originally posted by VisionQuest78 »
      correct me if im wrong, but wouldnt i not hear and feel the fuel pump working if the relay was bad? If the relay was bad, wouldnt the fuel pump just not work at all? the key word here is intermittent, sometimes they die slow deaths.

      The 99 AEB doesnt have an immobilizer. sorry, my bad.

      MAF is one i have considered also. That was why i cleaned it awhile back. I guess i could try unplugging it and see it starts... worth replacing anyway, esp if your MAF is 11-years old.


    10. Member gtiguy12's Avatar
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      03-25-2010 06:54 PM #10
      If the ecm doesn't see a speed signal from the Crankshaft position sensor, it will not send a signal to turn on the fuel pump. I have seen many fuel pump relays and pumps replaced due to a bad Engine speed sensor.
      Quote Originally Posted by VR6Vixen01 View Post
      In part, Jason has to run because it is faster than driving his car...

    11. 03-25-2010 07:01 PM #11
      Quote, originally posted by gtiguy12 »
      If the ecm doesn't see a speed signal from the Crankshaft position sensor, it will not send a signal to turn on the fuel pump. I have seen many fuel pump relays and pumps replaced due to a bad Engine speed sensor.

      I was kind of thinking along those lines too. But does the fact that the fuel pump is cycling eliminate this?


    12. 03-25-2010 10:12 PM #12
      So after some more reading and research the engine speed sensor seems even more likely. Most of the posts i have seen about it, they also had DTC's that came along with the sensor failing, but not all of them. I did see a test procedure, where you measure the resistance across terminals 1 and 2 and should get a reading 400-1000 ohms. And between 1 and 3 and 2 and 3 should be infinite. I will run this test tomorrow.

      I started searching for a replacement online, but im not having much luck. ECS was the only i found that had it, and it was $80 plus shipping. The main issue i think is that this called so many different things. Engine speed sensor, rpm sensor, G28 sensor, reference sensor...

      Does anybody have a good source for this part?


    13. 03-26-2010 01:23 PM #13
      well, i checked the resistance of the engine speed sensor and it was fine...read 454 ohms...

      But i found a wire that wasnt connected, to SOMETHING? There is a wire that splits into a y, one end has one wire coming out of it that connects right near the oil cooler. I think maybe it connects into what th eoil cooler is bolted down to.

      Then the other side of the y was a blade connector, and thats the connection that was loose. There is only a couple of inches of play, so it has to connect SOMEWHERE near the oil cooler, but i cant find the damn spot.

      I tried tracing the other end of the wires, and i THINK it goes into the main sheath that feeds into the ECU box. I was missing another set of hands and eyes to know for sure, but im pretty sure thats where it goes.

      Here are a few pics...


      This is where the connected part of the Y is (on the tip of my finger). To the left and under my hand is where the oil cooler is. You can see it in the pic, im just trying to help see....


      And this is what the blade connection looks like on the unconnected side of the Y....


      SOOOOO...does anybody know where this connects? Im not sure if ill be lucky enough for this to be my problem or not, but i figure bare minimum it needs to be connected to something...


    14. 03-26-2010 03:32 PM #14
      That sensor in the top of the oil cooler is the stock oil temp sensor I believe. If someone can confirm that, connect to vag-com and see if there is any readout as to oil temp.

    15. 03-26-2010 04:15 PM #15
      Quote, originally posted by kkkustom »
      That sensor in the top of the oil cooler is the stock oil temp sensor I believe. If someone can confirm that, connect to vag-com and see if there is any readout as to oil temp.

      I can go out and check with the computer and see, but i believe that sensor (if it is infact the oil temp sensor) is totally plugged in. There is a white wire going into it with a boot around it, by feel it feels like the same type of blade connection. This the connected side of the Y...

      The unconnected side is less than 2 inches long, so it must plug in SOMEWHERE near there.


      If anybody reading this has an AEB 1.8t engine, it would be GREAT if they could go out and trace where this plugs into!


    16. 03-27-2010 11:33 AM #16
      Quote, originally posted by kkkustom »
      That sensor in the top of the oil cooler is the stock oil temp sensor I believe. If someone can confirm that, connect to vag-com and see if there is any readout as to oil temp.

      I went out and hooked up vag-com and couldnt find any measuring block that was for oil temperature. Not that it didnt show a temp, just that i couldnt find any place that measured it. But i have a 3rd party cable, and i dont get all of the functions that come with rosstech one, but i do get most...

      And a bump for a fellow AEBer...PLEASE HELP! lol Just trace that wire and see where it connects....


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