Technical (Almost) no boost Grande Punto tjet

[SiriusNL]

Hello everybody,

I have a Grande Punto 1.4 tjet with vl38 turbo, that is the only thing that is not stock its remapped at a fiat garage, been working fine for over three years.

My problem started with a misfire and a catalytic converter error message. Since then there is almost no boost from the turbo, also i dont hear the turbo or blowoff anymore. I have replaced the cat and the problem still persists. There are no error messages coming up anymore so that is good. Also cleaned the MAP sensor, but that dit not help either.

I have use MES to find the issue but i am not a car mechanic and need your help. Please take a look at this graph because to me the pressure compared to desire pressure is off quite a bit.

Thank you in advance.

 

[AdamST205]

Have you checked to see if the turbo is all okay physically? These turbos love to crack their exhaust housings especially around the wastegate. If really bad will not make any boost as it will bleed it off constantly.

Really easy to check the hot side of the turbo. Just remove the cat.

 

[SiriusNL]

Thanks for your reply, the mechanic checked the exhaust side of the turbo while he replaced the cat. He said it looked nice, also he test the wastegate, that was also working as it should.
Today I've checked the air intake side and i also didn't see anything off. Checked all the hoses going to turbo and the clamps, they are all fine.

It all happened when i drove out our street at it started to run on 3 cylinders with engine check light, then i went straight home. Check error numbers and it shows P0303 and P0420, because it happened on my birthday i didn't have time to check that day. The next day it started and run just fine only there is no turbo pressure anymore, error codes are gone. Went to mechanic, he discovered that exhaust was leaking, fixed the exhaust and replaced cat because of P0420. That didnt make any difference at all.

So here i am figuring it out myself, bought MES kit and found out i'm missing knowledge on what sensors to read and what is a wrong reading or not. So i just checked all the hoses and cleaned the MAP sensor. No result

The engine runs fine no hickups or anything, only that its slow as hell with accelerating and top speed now is like only 170km/h.

 

[SiriusNL]

Added a new graph, maybe it helps

 

[SiriusNL]

Since no one is willing to help yet, here is more info

Things that have been done so far:
- Replaced cat
- Replaced air filter
- Fixed leak exhaust
- Cleaned map sensor
- Replaced boost solenoid + checked all the hoses connected to it.
- Replaced intake hose going to turbo (leak)
- Checked all the hoses and clamps coming from and going to the inter-cooler

Additional info:
No power going uphill
On highway boost is 1-2psi max, taking over is almost impossible.
Turbo looks good on both sides


Hopefully somebody can help me because i have done all i could.

 

[AdamST205]

Have you double checked the exhaust housing to see if it is cracked? Whatever your problem is it is 100% mechanical issue. have you checked to see if the turbo actually moves? It could be jammed against the housing and not moving at all.

You can remove boost solenoid control completely by looping the system with the turbo then your wastegate will do boost control to rule that out.

 

[varesecrazy]

Seriously low on power suggests it is a turbo issue, rather than intercooler

But always worth looking around the intake hoses

 

[SiriusNL]

I have checked the turbo at the intake side and it spins when i start the engine. I have had the manifold cracked once, it got welded, that could be a issue? Must be a big leak then, if i'm losing that much pressure. 6psi is max turbo pressure, its usually 14+psi

 

[AdamST205]

I have checked the turbo at the intake side and it spins when i start the engine. I have had the manifold cracked once, it got welded, that could be a issue? Must be a big leak then, if i'm losing that much pressure. 6psi is max turbo pressure, its usually 14+psi

The turbos crack on the exhaust housing which if severe will mean very little boost and you will be constantly leaking boost past the wastegate.

My VL37 had a cracked housing and the used VL38 I replaced it with had a cracked housing too so extremely common. Replacement housings are not that expensive though and come with all the gaskets needed.

This was my old one. Cracked in two places.

 

[SiriusNL]

The turbos crack on the exhaust housing which if severe will mean very little boost and you will be constantly leaking boost past the wastegate.

My VL37 had a cracked housing and the used VL38 I replaced it with had a cracked housing too so extremely common. Replacement housings are not that expensive though and come with all the gaskets needed.

This was my old one. Cracked in two places.

Thank you for the info
This Wednesday the car is going to garage and the mechanic will take a closer look and do some pressure test(smoke). Also i checked for codes and it gave me; 'P0240 Turbocharger Boost Sensor B Circuit Range/Performance' no engine light.

Are there any other things the mechanic could take a look at?

​

 

[SiriusNL]

The mechanic was sick so i had to do it myself.

Found a big crack in the exhaust housing like you said, replaced the housing. The only problem is that the car runs the same as before. Same boost levels. Like it didn't make a difference at all.

So what now?

 

[SiriusNL]

New test run MES. On my boost meter it reaches 0.50 bar maximum.