Skyline Owners Forum banner

1 - 3 of 3 Posts

·
Registered
Joined
·
2 Posts
Discussion Starter #1
I just got a R33 and have been working on it just over a month now with a friend. Since received the car has had boost issues whenever it's under throttle. Sometimes the boost gauge doesn't go past 5-7psi with the car sputtering like crazy under acceleration. Other times the boost gauge shoots way past 10psi almost instantaneously. First we checked the compression to find 170-180psi across all 6 cylinders (most were 180). We then removed the plugs, cleaned them, gapped them (0.035-0.040) and re-installed. No difference. We heard an air leak from the intake side when we first got it, so we took off the manifold and replaced all gaskets and hoses. The air leak was gone but the problem persisted. We took out the factory fuel pump and filter, put in a new filter and a 340lph fuel pump. Problem persists. We tried two aftermarket manual boost controllers. We used every vacuum diagram on the web for a R33 boost solenoid (sadly there are literally guides stating that every way to run the hoses is correct). We removed the heat shield to the turbo and could move the wastegate manually, so chances are it isn't stuck. Problem persisted. We then ran a hose directly from the charge pipe (coming off the intercooler to the intake pipe), directly to the wastegate (bypassed the solenoid) which should give us 5-7psi. The problem persists.

When you're driving anywhere below 3psi the car runs like normal. It has a factory ECU with zero codes. Stock turbo, stock intercooler, stock piping. The only aftermarket mods are HKS plugs, Apexi Filter, and downpipe/exhaust. Neither of us has any idea why this car continues overboosting causing a horrible sputter. We appreciate any help this community can offer.
 

·
Super Moderator
Joined
·
8,984 Posts
Several things to try....first what heat range are the plugs? by what you describe i would be looking at the turbo waste-gate and the actuator to see if its sticking/failing.... it could also be the coil packs failing/shorting which is a common problem.
Chronic misfire can also be due to lean or rich mixture so also check the fuel pressure regulator and its vacuum line.
 
  • Like
Reactions: GTSport

·
Registered
Joined
·
2 Posts
Discussion Starter #3
Thank you for the feedback. The wastegate was moving fine by hand, and when I hooked up a 5psi source to it, it moves just fine. No idea why it was overboosting. We checked the fuel pressure and it's a bit higher than it should be, which I've read happens sometimes when you go with a higher lph pump due to the extra fuel being returned to the tank causing a bit of a pressure buildup. We took some coilpacks off another RB25DET, swapped them on, and sure enough that was it. Set the timing and now she runs perfectly!
 
1 - 3 of 3 Posts
Top