Misfires fixed!

After many hours of head-banging I finally solved the misfire issues! I had previously compiled a list of possible issue that I used as a checklist for eliminating possible faults one by one. 

Now, lets review the list of suspects from an earlier post:

  • Bad coilpacks
  • Bad gas (water etc.)
  • Bad spark plugs
  • Bad MAF
  • Vacuum leak
  • Low fuel pressure
  • Bad crank position sensor
  • Bad O2 sensor
  • And several others.

From just about every post and article I read on the internet, coils and plugs were on, or near, the top of the list of usual suspects. I had previously upgraded coils and plugs when I tuned the engine to stage one back in november 2016, so I figured they were OK. I did fix a few vacuum leaks thinking it was it, but the problem was still there.

I then went on and replaced the following items:

  • Spark plugs
  • MAF
  • Crank position sensor
  • O2 sensor
  • Fuel filter
  • MAP sensor
  • PCV valve
  • PCV check valve (pancake valve)
  • Misc. check valves

As it is a 15-year old engine, most of these parts needed replacement anyway, so I figured this was a golden opportunity to get it done. Unfortunately it did not resolve the misfire issues and I was running out of ideas.

As a stroke of luck, I got a hold of four coils from my brothers 2001 VW Passat before he sent it to the scrappers. I threw them in there to see if it made any difference – and voilà – the engine purred like a kitten!

Lots of work, lots of parts changed and the issue was what everyone said it would be… Lesson learned, listen to the majority and change the obvious culprit first.

Turbo Inlet Pipe v2.0

As I am afraid of water entering the inlet system, I decided to rebuild the turbo inlet pipe. I had initially though of going this route, but as space is tight, I mean really tight, I didn’t do this the first time around.

Since the 90degree pipes I already had didn’t have a sharp enough bend, I had to improvise and create a sharper bend by cutting the 3in pipe in a 45degree angle and weld the two parts together. I suspect this might not be the best solution as air have to pass through the sharp bend just before the turbo, but it’ll have to do for now. I also had to reroute the crankcase ventilation system in order to fit the PVC pressure release valve (which I’m replacing because I suspect it being bad).I reused some of the original piping and rubber bends to route the system close to its original path. This turned out pretty good and actually looks quite nice! 

I’m currently waiting for a 3in to 2.75in silicone reduction hose to fit the original mass airflow meter to the 3in intake pipe so I cannot test it quite yet, but it will be nice to hear how it sounds. The previous turbo inlet pipe (first version behind the fog-light) was a bit longer than the original one which resulted in the dump valve being almost inaudible from inside the car.

Since the air inlet is now very close to the exhaust, heat might become an issue. I decided to modify my old heat shield (created from an old computer case) and placed it in between the turbo and the air filter.  

I’m attaching some pictures from the build, but remember – I’m not the best welder… Still learning though 🙂

Vacuum and misfire issues

Time for an update. I got the engine running a little a few weeks back and at first it looked like it was going well. The engine started up as it should and idled normally. I ran the engine at idle for a little while just to warm it up and listen for unusual noises. All temperatures were in the green so I decided to go for a test run. I ran the car lightly at first just to make sure things were running smoothly before I did a slight pull when running up a hill. The turbo started charging and everything looked good, but then, misfires. A lot of misfires. I pulled over to a parking lot to do a quick visual inspection (the engine was still running) but couldn’t see anything. As quickly as the misfires came, they disappeared. I did another light pull and this time it behaved normally. I decided it was a one-time thing and went for a longer trip while still driving pretty lightly. It ran fine for about 10 to 15minutes before I went for a pull in second gear. Like before, it started to misfire, this time more severe. I pulled over to see if any of the pressure hoses had come loose, but they were all fine. I had my VCDS running and it was showing random misfires on all cylinders as well as the lambda O2 header element being bad. After a restart of the engine, the misfires were gone. I drove home to do a more thorough inspection of the engine compartment and found the crankcase breather pipe (the plastic 90degree one) was completely broken.

I did some research and found quite a lot of reasons for why the engine might misfire randomly on all cylinders:

  • Bad gas (water etc.)
  • Bad coils
  • Bad spark plugs
  • Bad MAF
  • Vacuum leak
  • Low fuel pressure
  • Bad crank position sensor
  • Bad O2 sensor
  • And several others.

I quickly ruled out coils and plugs since I find it strange that they should all fail at the same time. They are also less than a year old. The misfires should also be there (to some degree) all of the time, not intermittently like the ones I had.

A vacuum leak is pretty common for these engines, and since the crankcase breather pipe was broken, I decided to get a new one. I also ordered a new O2 sensor, the PCV valve, a few hoses and a crank position sensor. When removing the intake manifold, I saw a few vacuum hoses being worn down so I decided to replace them as well.

After replacing the O2 sensor, the crankcase breather pipe, the PCV valve, the crank position sensor, a few vacuum hoses as well as the intake manifold gasket and the throttle body gasket I has high hopes that the issue was resolved. To my disappointment, it was not. When going out for a test-run it ran fine at first, but the misfires all came back when I did a light pull. I managed to get back home and did a quick check as well as changing the spark plugs. No immediate change with new spark plugs, which was expected, but as it is a relatively cheap fix I decided to just get new ones. Using VCDS I saw that the short term fuel trim was fluctuating between -2 and 2% and the long term fuel trim was stable at about 3.2%. I read that the long term fuel trim should normally be a little lower so I cleared DTCs and saw the short term values being very high at more that 25%. After a few minutes, the long term increased to about 3.2% and the short term stabilised between -2 and 2% like before. I deduced that it had to be a vacuum leak somewhere, but was not able to find any so I went in to grab some food and do some research.

As I couldn’t find a obvious vacuum leak, I decided to replace the PCV relief valve (pancake valve on the TIP) as it’s now about 16 years old and is likely to be passed its prime.. When removing the intake piping where I found some water having gathered there. That is most certainly not good since it could be sucked up by the turbo when doing a pull, getting mixed with the fuel and wrecking havoc with the fuel mixture… I decided that I have to rebuild the intake to move the air filter up into the engine compartment. The problem with this is that it’s a very tight squeeze getting a 3in hose passed the headlight…  

That’s it for now – I’ll update once I have some news 🙂

Air filter splash shield

As I said in my previous post, I’m worried that water may enter the air filter and cause some issues when driving in wet weather. This is because I have moved the air filter down behind the front bumper fog light. I had a small bit of metal plate laying around from my previous heat shield which I modded to fit around the bottom and front part of the air filter. It’s not the prettiest thing, and it will not prevent large splashes from entering the air filter, but it might help keeping the worst of it away. To prevent the air filter from moving to much, I made a couple of rudimentary brackets as well.

I also discovered a couple of bumps in the intercooler piping close to the turbo, which I suspect may be from parts being slung out when the previous turbo died. Need to check if there are some broke turbo parts in the intercooler before I fit it all together again.

Custom downpipe and turbo inlet pipe

As I’m fitting a non-standard turbo, I had to manufacture a new downpipe for the exhaust and a new turbo inlet pipe in addition to several other hoses and fittings. As I have never done this before, it was a good learning process and the result did turn out well enough.


The main goal here is to create a short pipe section that runs from the turbo to the original post-cat exhaust stub as the original cat does not fit the new turbo. The turbo (GT2860RS) came with a short 5-hole to 3in v-band fitting. For the other end, I cut of the other flange from the original cat. I bought several 3in pipes and bends in addition to a 3in to 2.5in reduction pipe as the original flange did not fit the 3in pipe directly. I welded the pipe together using a MIG with flux-core thread, which turned out ok, but the flux-core creates a lot of spatter and take a lot of work to get “pretty”. I might invest in some gas for my next project…

Turbo Inlet Pipe (TIP)

As the original TIP didn’t fit the new turbos 3in inlet port, I had to make a new one. In addition to this, the new turbo sits closer to the front of the car than the original one making it hard to route a 3in pipe passed the headlight to the original position of the air filter. I had to route the pipe downwards under the front-bumper brace and outwards to the right side just behind the fog-light. I’m worried that this might cause issues in heavy rain if the air filter sucks in water, so I might create some kind of a shield protecting the air filter from water splashes.  

Oil pan and failed turbo particles

When I changed the oil-return pipe, I noticed something that looked like ball-bearing parts sitting in the oil-return hole in the oil pan. I decided to take of the oil pan to clean it and at the same time clean the oil-pickup pipe for the oil pump. Good thing I did as I found more shattered turbo-parts in the oil pan when I got it off the engine. I also found one of the engine mounts being broken, so I decided to replace both. I am also replacing the front engine snub mount and the sway bar end links.

Turbo downpipe mockup

Since I’m swapping to a new turbo and exhaust manifold, the old cat doesn’t fit the new flanges and position of the turbo. Bought me some exhaust pipes at Biltema the other day and did a test fitting earlier. Now I just need to get some welding equipment so I can weld it together.

Test fitting the new turbo

Ever since my turbo broke down just before the summer, I’ve been looking forward to getting back into the garage to pick it apart to see what had happened. It seems that the shaft snapped clean off at the compression side of the turbo causing the housing to crack open. I’m not sure what caused this, but it could be that the shaft had too much play since the bearings were worn down and it basically self destructed… My plan is to fit a Garret GT2860RS using a high-flow manifold with a T3 flange and fabricate a custom down-pipe instead of the original cat. I will also need to make a custom turbo intake pipe with all the fittings needed for it.


Hei og velkommen tilbake! Nå er det på tide å skrive litt igjen. Grunnen til at all historikk er borte er at jeg fikk ødelagt databasefilene også orket jeg ikke bruke masse tid og energi på å forsøke å få de gjennopprettet. Fresh start sier nå jeg!

Vi har kjøpt oss hus! Og mest viktig av alt – vi har nå egen garasje! Jeg har brukt litt tid på å sette i stand garasjen, da med gulv, maling og arbeidsbenk så nå er jeg klar for litt mekking igjen.

Følg med fremover så kommer det nok en oppdatering i ny og ne 🙂