In my (completely anecdotal, take it with a grain of salt) experience, typically the underboost code only pops when there's complete turbo failure. You can pop the bumper off to look for damage to the intercooler and other intake tubing yourself, or run a smoke test to pressurize the entire intake system which will show you the same thing.

You can check voltage and resistance across those sensors yourself. Hyundai Veloster 2011-2017 Service Manual has the majority of technical information regarding sensors and whatnot. That site is for the N/A but much of the information carries over to the Turbo. Keep in mind there are two sensors you need to check: one on the front of the intake manifold and one on the cold side of the intercooler.

Once again, take it with a grain of salt, but here's my personal take: your turbo is probably bad. Deferred maintenance on these cars is PARTICULARLY damaging, especially oil changes. When I got my VT (and was a lot worse educated on it) it had not been taken particularly well care of. Oil grime visible inside of the valve cover, too long change interval, wrong oil grade, etc. Nothing fixed the underboost code until the turbo was fully replaced. I certainly hope that's not what you're looking at but keep it in mind. Replacing all these sensors (that might not even be bad) will cost you a ton on top of replacing the whole turbo assembly, if that ends up being your issue.

Also worth noting my underboost code would only pop on occasion under fairly high load. Car would go into limp mode and then revert to normal on restart. I drove it for a good long while during this, including while "limping" and the car seems to still be okay.

What other codes are popping? Do you have a code reader to look for yourself? What was the oil change interval and what grade of oil / kind of filter are you using?

 

In my (completely anecdotal, take it with a grain of salt) experience, typically the underboost code only pops when there's complete turbo failure. You can pop the bumper off to look for damage to the intercooler and other intake tubing yourself, or run a smoke test to pressurize the entire intake system which will show you the same thing.

You can check voltage and resistance across those sensors yourself. Hyundai Veloster 2011-2017 Service Manual has the majority of technical information regarding sensors and whatnot. That site is for the N/A but much of the information carries over to the Turbo. Keep in mind there are two sensors you need to check: one on the front of the intake manifold and one on the cold side of the intercooler.

Once again, take it with a grain of salt, but here's my personal take: your turbo is probably bad. Deferred maintenance on these cars is PARTICULARLY damaging, especially oil changes. When I got my VT (and was a lot worse educated on it) it had not been taken particularly well care of. Oil grime visible inside of the valve cover, too long change interval, wrong oil grade, etc. Nothing fixed the underboost code until the turbo was fully replaced. I certainly hope that's not what you're looking at but keep it in mind. Replacing all these sensors (that might not even be bad) will cost you a ton on top of replacing the whole turbo assembly, if that ends up being your issue.

Also worth noting my underboost code would only pop on occasion under fairly high load. Car would go into limp mode and then revert to normal on restart. I drove it for a good long while during this, including while "limping" and the car seems to still be okay.

What other codes are popping? Do you have a code reader to look for yourself? What was the oil change interval and what grade of oil / kind of filter are you using?

No other codes according to the dealer, Synthetic oil, not sure on filter or change intervals(probably not frequent enough)/ They didn't clear codes but I think I will disconnect the battery later today and see I can get the codes to clear and see if they show up again. Thx for the link!

So it sounds like it's ok if she drives it while I work this out?

 

Underboost code can also be caused by loose charge pipes, faulty solenoids and a torn BOV.

 

I retract my previous statement lol

 

As someone who just recently had a turbo failure... P0299 and a loss of power sounds exactly like what just happened to me. If you're not seeing white smoke out of the exhaust or pcv systems then that's a better sign. Check the hot pipe (hose from turbo to intercooler) for oil too. If you really want to get your hands dirty you can take off the down pipe or the turbo inlet pipe and check for any wiggle with the shaft.

I don't think you need to check those sensors or anything else as they normally read completely different codes.

 

P0299 will be from a boost differential of more than ~4 psi from what the ecu thi ks the car should be making. So check for boost leaks. Nothing else needs to be checked until you're sure no boost leaks. If you get no power due to code, shut car off and power is back, this is good sign no mechanical or electrical issues and solely a boost leak.

Common areas are the hot pipe leaking somewhere and the BOV diaphragm having small tears/holes.

Report back ill gladly walk you through the fix.

 

awesome appreciate the help, how do you check for leaks on this pipe? Just check fittings are secure?

 

I suggest remove the pipe, clean all sealing surfaces, inspect all components for any defects that may cause leaks, then reinstall. During reinstall I'd use a better clamp than a spring clamp on the resonator section that the oem provides but this is not needed if everything is installed properly.

 

I have had that experience with the code. Especially if the car isn’t making what it wants lol

 

update from yesterdays work..... no success in finding the leak, I need more help in diagnosing where the leak is. We made the Home Depot boost leak test kit which allowed us to push in compressed air at the turbo. Not sure if we should have capped the line anywhere else or what but air flowed freely into/out of the system. We sprayed all connections with soapy water and got nothing showing a leak. my guess now after thinking about it is we should have capped the line somewhere else... I just don't know much about turbos.
See my video link of what it sounds like when we push air in from the compressor, there is a thud and then the air seems to flow even faster, is this the waste gate opening/closing(after we stop pushing air)?

Posting a pic of the intercooler that looks beat to hell IMO, I'm sure that could be an issue also. Took the BOV off and compressed it, put my finger over the end and it held in place so no issue there, rubber seems to be in good shape.

Whats the bulge in this line, see pic., check valve? The line has some cracking in and probably needs to be replaced.

and a pic of my dads DeLorean for sale in you know anyone $65K

 

Yeah that check valve is normal for the evap line

 

Boost leak test requires it holding pressure and you knowing what the pressure is as well. So yes it needs to be capped. Once under pressure you need to see it leaking down and sometimes you can hear it. Other times it requires soapy water or smoke to find it.

 

ok so where to cap the other end if we are forcing air in where I show in my video?

 

The cold pipe outlet is #1 or intercooler outlet is option #2

 

Sorry for the long delay...vacation ya know. Ok so we borrowed a smoke machine today and blocked off the intake where it meets the hard pipe on the top backside of the engine and forced the smoke in thru the brake booster line. The smoke was coming out of the vacuum pump assembly which is directly below the intake on the front drivers side of the engine. See my video of the smoke coming out of the vacuum pump. SO did we do the test right? Should there be smoke coming out of the vacuum pump? Vacuum pump is a $500 part. ALso there was a fair amount(enough to cover my finger in oil) oil when we took apart the intake on the rear side of the engine, where we blocked it off, see pic. Should there by some oil in there? NOTE there was no other place where smoke was coming out, only at the vacuum pump....the mystery continues.....as always any help is appreciated.
Derek

oil in intake piping

 

The oil can be normal from the breather hose and the blowby from the engine. Clean it up and move on. There are ways to prevent this if you wanted to do so later.

I just had a customer report to me the other week having the same issue and boost leak at the vacuum pump. He replaced it and it fixed the car. Do not pay $500 for one.

Do be sure that everything that see boost is tested if possible before making any fix.