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    Thread: A weird problem with my 1.6 8v Golf MK4

    1. 01-05-2020 04:40 PM #1
      Car is VW Golf MK4 1998 1.6sr AKL engine, fitted with LPG.

      I'm looking for a solution for a problem that I've been trying to fix for the last couple of months.
      The problem I'm experiencing is this: the car starts really easily in the morning, goes immediately up to 1100-1200rpm (I think this is normal when the engine is cold), but after 5-6 seconds, the RPMs start going down pretty fast, the engine is misfiring like crazy, and it just starts sputtering in the 300-800RPM range. There is a very strong petrol smell from the exhaust. If i press on the gas, the misfiring stops at the higher RPM's but the RPM's go reeeaaallyy slowly up and down (even if I just blip the throttle a bit, the rpm's will surge up to 2000 very slowly, and slowly come back down). As the car warms up the problem gets better almost linearly. As soon as the car automatically shifts to LPG, it's running great and idles great, except for a small flat spot when pressing the gas. When the car gets up warmed up, it's working really well.

      I've scanned it with VAG-COM, and I got a 00537 - Lambda Regulation: Lower limit. Even when the engine is warm, if I let it idle i can see the lambda regulation values slowly go up to minus -25%, but if i blip the throttle the value goes up to 0% instantly.

      So far, I've changed the O2 sensor, coolant temperature sensor, the fuel pressure regulator, cleaned the throttle body and adapted it, cleaned the MAF (and tried with one from another AKL golf), used a fuel cleaning additive, PCV breather valve, N80 valve, and the plastic hose that goes from the MAF to the throttle body. I just can't seem to fix this thing.

      I haven't checked the spark plugs since it works great on LPG, but I'm not sure about anything anymore. Any help is appreciated.

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    3. 01-17-2020 05:21 PM #2
      Is that a American car? How much hp is it making?

    4. 01-18-2020 06:59 PM #3
      Looks like throttle body idle stabilization isn't working. Warm engine will work without it. Maybe faulty throttle body. If it will be older engine it will has ISV.

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    6. 01-26-2020 08:26 PM #4
      Quote Originally Posted by Anthony's View Post
      Is that a American car? How much hp is it making?
      It's supposed to make 101hp. It was bought in germany originally.

      Quote Originally Posted by dogzila22 View Post
      Looks like throttle body idle stabilization isn't working. Warm engine will work without it. Maybe faulty throttle body. If it will be older engine it will has ISV.
      I'll make sure to check it out, thank you. One thing that steered me away from the throttle body is the thing that while the engine is cold, if I change between LPG and petrol, LPG works like a charm, while if I switch to petrol it starts misfiring again.

    7. 01-31-2020 06:58 PM #5
      fuel filter or pump maybe

    8. 02-01-2020 09:13 PM #6
      Throttle body ruled out, same problem with one swapped from a working car. Fuel filter is changed about 20 000km ago. Fuel pump is the original one. Can a bad fuel pump cause overfueling?

    9. 02-02-2020 02:30 PM #7
      if you lack fuel pressure it will affect the injector spray pattern. they will drip instead of atomize the fuel.

    10. 02-09-2020 09:55 PM #8
      Fuel pump turned out fine. I'll ultrasonic clean the injectors next and recondition them, replace the gaskets on the intake manifold, change the valve stem seals (it drinks oil like mad) and readapt the throttle body again. Wish me luck

    11. 02-09-2020 10:10 PM #9
      have you changed the fuel filter? does the lpg have seperate injectors?

    12. 02-09-2020 10:11 PM #10
      could be oil fouled spark plugs too.

    13. 02-12-2020 12:24 PM #11
      Quote Originally Posted by garryt View Post
      have you changed the fuel filter? does the lpg have seperate injectors?
      The fuel filter has about 20000km on it, and yes, the LPG does have separate injectors.

      Quote Originally Posted by garryt View Post
      could be oil fouled spark plugs too.
      I checked two of the spark plugs a few days ago (I can only access two without removing the intake manifold) and they were clean(that doesn't mean the others were clean too), BUT, the car does burn quite a bit of oil - i've added about 3 liters of oil the last 5000km. I'll be replacing the valve seals soon.

    14. 02-12-2020 03:57 PM #12
      it could be your piston rings causing the oil problem. what mileage is on the car?

    15. 02-12-2020 04:00 PM #13
      that works out pretty much the same as my oil consumption before I swapped motors. no issues with misfires though.

    16. 02-16-2020 04:27 PM #14
      Quote Originally Posted by garryt View Post
      it could be your piston rings causing the oil problem. what mileage is on the car?
      It's got 225000 km or 140000 miles.

      It might be the piston rings too, but the smoke isn't there all the time, only when starting the car in the morning, and when waiting at a light. It smokes quite a bit until it warms up, then it's fine except if the weather is pretty cold, in that case it makes white smoke (I think this is normal water condensation).

    17. 02-21-2020 02:57 PM #15
      At long last, I found out the culprit. Or should I say, culprits.

      The 00537 Lambda Regulation: LOWER LIMIT was cause by a leaking membrane in the LPG regulator. It was mixing LPG and petrol at the same time and causing the code.
      BUT, after shutting off the LPG system completely and closing the valves (essentially removing the system from the car), there was a NEW code: 00537 Lambda Regulation: UPPER limit.
      After looking for vacuum leaks for a while, I narrowed it down to a vacuum leak from the intake manifold gaskets (4x rubber rings) and partially clogged petrol injectors.
      The LPG was fixed, new gaskets where installed and the injectors got some ultrasonic cleaning treatment. The car is running like new! Except of course, the oil disappearing somewhere.

      Thank you for your help!

    18. Yesterday 10:26 AM #16
      always nice when someone posts a result you could try changing the valve stem seals with the head still in place. but if you're going to remove the head, you really should do the rings too

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