another engine problem.

[d40ryan]

ok so heres the issue 2007 rx yd25 d40
now the turbo blew up a couple weeks ago (broken fins exhaust side)
couldnt get new one but managed to get one off a wreck.

now heres where it gets interesting, new turbos all bolted up sweet took for a drive and was making boost drove for 5 min and then it spiked and read -14 on boost gauge and as if stalled the car, i clutched it as this happened and pull over the car was still running all good took off again come home checked lines all looks fine.

took for a test today drove fine again making boost and what not. but i did notice it spike really quickly to '14 once with no stalling engine locking up issue.
so turned around quick to come home and on the way it did it again but this time i didnt get clutch fast enough and it fully stalled the car registering -14psi on the gauge and the dash went to as if it was on ignition. just lucky it was only a second up road and i could roll home clutching.


thoughts on why the car would be going into -14 psi while driving?

 

[unkn0wn]

a diesel should not read negative on a boost gaudge, i have only had this occur when my oil seal went and the turbo was not spooling corectly
- the engine is trying really hard to suck past the restriction, thus creating Vac

I would look for pipes getting sucked closed, this will cause it (happens when hot usually)
Did you leave a rag in any of the pipes when changing turbo? this will cause it.
Is your airfilter a pile of mud? this will cause it.
hopefully you can see where im going with this? super intake restrictions, look for them.

possibly something to do with the variable van turbo controller too...wouldn't put it past that thing...

 

[Old.Tony]

I'm wondering about the actuator as well. There's no saying the actuator on the 'new' turbo is 100%, so have a look at its operation first.

Let the car idle and pop the bonnet, look at the arm beneath the actuator. It should rise and fall over a few mm of range. If you can now get someone to raise the RPM to around 1500 and let it go (repeat) you should see a synchronous rise and fall of the shaft.

If the actuator misadjusts the turbo vanes, the turbo will not get as much spin and the engine could suck more air than the turbo is delivering (normally a turbocharger is spinning enough to always provide at least a small amount of boost, unless you're extensively engine braking).

You might consider exchanging the actuator on your old turbo for this one and see how it goes. Also check ALL of the vacuum lines and joins. A stiff piece of hose is prone to cracking and loosening on the joiners.

 

[d40ryan]

actuator seems fine, car is making boost normally on the gauge and the actuator is moving correctly and it only happened after a few mins off driving once everything is hot...... could intercooler hot side pipe be cause this as it is that flimsy rubber, evan they i dont know why it would be making vacuum when turbo is making boost through the intercooler?? could it have anything to go with the egr set up as pipe has now been blocked off both sides, (wouldnt think so as its only egr?)

also pipes were blocked with alfoil to try and prevent the rag situation and all was removed.

also another funny thing is old turbo was making 29psi when you put your foot to floor, new turbo is doing same could this have something to do with it?

 

[Old.Tony]

29psi of boost is pretty high but it's not an engine killer. Bluenavara (a user here) develops something like 36psi in his (I think he changed his turbo to something else, but the engine is coping).

Intercooler and charge air hosing issues can cause problems, but I'm not sure they'd make it look like "-14psi".

Thinking about that a little more, "14psi" (with rounding error) is atmospheric pressure (14.7psi) and it's possible that what you're seeing is either a loose sensor cable, a faulty sensor, a faulty earth path to the intercooler - it would be worth taking the electrical connectors apart, giving them a clean and reassembling.

Hose flexing will feel like lag but it'll still produce boost and when the hose "deflates" it shouldn't go negative and stall the motor. It's possible that the ECU is monitoring the boost pressure and, on seeing a negative amount, reduces the fuel rail pressure (engine braking). If you have a means of measuring fuel rail pressure, see how that varies at the time the boost seems to play up.

 

[d40ryan]

wondering all night the actuator wouldnt cause it to read negative as it only makes spool speed? as my solenoid was playing up for a while there and the turbo wasnt working but the car still ran as there was air flowing straight through the turbo.

would the wastegate shut the path to the intercooler which would cause it to make negative vacuum as it is sealing? i cant see the hot pipe being able to suck itself togeather to make such a negative pressure.

these are all hyperthetical as i dont know much about the insides of these vvts and how they work.

also the boost gauge is off the pressure sensor so it has to be sealing somewhere after the cold pipe, so intercooler-hot pipe - turbo-airbox.

so would there be something in the turbo that blocks the path to intercooler.

oh and the fuel pressure thing when i said stalling i ment like full compression lock, like going from third to first and dropping the clutch.

also no fault codes are coming up i have an obd2 adaptor and torque2 and have scanned and it says no codes stored, is there a special process that needs to be done to put it into code recovery mode just to see if there actually is anything there, although if it was a fault code would the car have gone into limp mode?

 

[Old.Tony]

No codes found means just that, and if your Check Engine Light is off, the car doesn't think anything's wrong.

The turbo vanes can help it spool up harder, but if they relax, they aren't going to push the turbo hard at all.

If that pressure sensor disconnects and the ECU thinks there's zero boost happening, it could cut the fuel rail pressure to prevent it from overfuelling. That's why I asked what the rail pressure was like at the time.

The charge air hose (between the turbo and the intake manifold) should never collapse. Expand sure, under pressure from the turbo, but never collapse unless there's a blockage in the air path - and a rag in the pipe doesn't come and go randomly, so it's unlikely to be a collapsing charge air pipe. The intake pipe between the air filter and turbocharger is sturdier and shouldn't collapse (the stock Nissan tube is quite firm).

In the Torque app, create a graph of your fuel rail pressure and watch it. When the disaster happens, take a look at the graph. My fuel rail pressure rarely falls below 4,000psi - if yours is going lower, it might be that boost sensor with a faulty electrical connection.

 

[tanz]

I once saw a Land Rover intake hose delaminate internally and a flap of rubber would fold over and block the intake, this would cause negative pressure. Maybe worth a look?!

 

[Old.Tony]

I once saw a Land Rover intake hose delaminate internally and a flap of rubber would fold over and block the intake, this would cause negative pressure. Maybe worth a look?!

Was it turbocharged?

 

[d40ryan]

could loose active on battery have caused the issue..... have checked terminals and all conections to sensors and they all seem fine, only slightly loose active terminal. drove for 20ks through round about with various drive styles and couldnt get it to fault.

checked with torque tony and its like 4g+(cant rememeber exactly) at idle then would go up with acceloration and drop back down when clutched.

im getting quite sick of these new diesels with all this electronics (and im an elecetrician)

 

[Old.Tony]

A loose positive terminal will make operations erratic, for sure. Could it cause your symptoms? I suppose, dodgy electrical connections can make any random shit happen!

Fuel rail pressure sounds normal. It should peak no higher (ever) than 30,000psi. I've not seen mine over 24,000psi and that was hauling the caravan up to Thredbo.

Let's hope it was the loose terminal.

Aside: while you're watching the fuel rail pressure, you'll notice that it varies all the time - even at idle. That's the ECU checking that your heated oxygen sensors (HO2S) in the exhaust are working properly.

 

[pace]

In the Torque app, create a graph of your fuel rail pressure and watch it. When the disaster happens, take a look at the graph. My fuel rail pressure rarely falls below 4,000psi - if yours is going lower, it might be that boost sensor with a faulty electrical connection.

Gday Tony,

1st time poster though long time viewer.

Q: re torque app, is there any way you have managed to view exhaust gas temperatures?

I have used torque and really like it, especially when towing van.

Cheers Pace.

 

[Old.Tony]

Gday Tony,

1st time poster though long time viewer.

Q: re torque app, is there any way you have managed to view exhaust gas temperatures?

I have used torque and really like it, especially when towing van.

Cheers Pace.

Welcome then!

Not in my car. My D40 doesn't have EGT sensors. They should be Mode 1 PID 78 and 79, but I get no response from those and I know that EGT sensors aren't fitted to my exhaust. There's a heated oxygen sensor, but that's useless.

I've actually got a Jaycar kit to make a thermometer designed for temps up to 1200C, but I haven't figured how I'm going to electrically isolate the probe in the exhaust stream so I haven't even started building the kit.

 

[pace]

Welcome then!

Not in my car. My D40 doesn't have EGT sensors. They should be Mode 1 PID 78 and 79, but I get no response from those and I know that EGT sensors aren't fitted to my exhaust. There's a heated oxygen sensor, but that's useless.

I've actually got a Jaycar kit to make a thermometer designed for temps up to 1200C, but I haven't figured how I'm going to electrically isolate the probe in the exhaust stream so I haven't even started building the kit.

Thx Tony, l will research mentioned. Though I am a Pathfinder driver, I am a fan of the Navara too. Seeing the common drive train between vehicles, I have utilised this forum to assist in my knowledge thrist for diesel YD25.
I'll post up a new member thread soon.
Cheers Pace.

 

[d40ryan]

A loose positive terminal will make operations erratic, for sure. Could it cause your symptoms? I suppose, dodgy electrical connections can make any random shit happen!

Fuel rail pressure sounds normal. It should peak no higher (ever) than 30,000psi. I've not seen mine over 24,000psi and that was hauling the caravan up to Thredbo.

Let's hope it was the loose terminal.

Aside: while you're watching the fuel rail pressure, you'll notice that it varies all the time - even at idle. That's the ECU checking that your heated oxygen sensors (HO2S) in the exhaust are working properly.

hmm where abouts is this sensor as my egr is broken atm and capped off:s no heater for me for a while

 

[Old.Tony]

Don't worry about the HO2S. It's in the exhaust, just before the CAT. It measures the level of oxygen present in the exhaust stream - the more oxygen, the higher the voltage.

This sensor actually has two uses. First it determines if there's enough oxygen present in the exhaust for reductant (any hydrocarbon will do, in our cars it's diesel fuel) to be added to the exhaust for the CAT, and the second is described above. The ECU raises and lowers the fuel rail pressure by a nearly imperceptible amount, but enough to adjust the oxygen levels in the exhaust (more fuel = less oxygen). The ECU monitors the HO2S response and determines whether or not the HO2S is working properly. That's one of the reasons why a computer-controlled idle is never 'stable'.

The EGR doesn't have a sensor, if I recall it's just a flow rate sensor to determine if there's anything flowing which is why in some cars, just blocking the EGR makes it throw the CEL.

Blocking the EGR shouldn't stop your heater from working!

 

[d40ryan]

Don't worry about the HO2S. It's in the exhaust, just before the CAT. It measures the level of oxygen present in the exhaust stream - the more oxygen, the higher the voltage.

This sensor actually has two uses. First it determines if there's enough oxygen present in the exhaust for reductant (any hydrocarbon will do, in our cars it's diesel fuel) to be added to the exhaust for the CAT, and the second is described above. The ECU raises and lowers the fuel rail pressure by a nearly imperceptible amount, but enough to adjust the oxygen levels in the exhaust (more fuel = less oxygen). The ECU monitors the HO2S response and determines whether or not the HO2S is working properly. That's one of the reasons why a computer-controlled idle is never 'stable'.

The EGR doesn't have a sensor, if I recall it's just a flow rate sensor to determine if there's anything flowing which is why in some cars, just blocking the EGR makes it throw the CEL.

Blocking the EGR shouldn't stop your heater from working!

looks like my pov pack lucks out again. theres no sensors on my exhaust at all ive pulled cat apart fully and no cables were attached... also i have a coolant lines running across the egr my assumption was for the heater as it went back to ac.... and now that its gone both sides makes cold air on hot....

 

[Old.Tony]

This sensor has to be there somewhere further up - it doesn't have to be right on the CAT, because oxygen levels won't change between the sensor and the CAT so it could easily be in the dump pipe.

The hoses going to the EGR cooler do indeed feed from the heater matrix inside the cabin. Just find the two and join them, rather than plugging them - or were the hoses removed completely?

 

[d40ryan]

pipes still attached atm didnt want to pull to much apart,

ive pulled the entire exhaust systems off including the exhaust manifold from side of motor and hollowed the cat out.... there was no sensors on mine.....

 

[Old.Tony]

The heater matrix is actually fed by the output from the EGR cooler (if you have the manual, have a look at the diagram on page 36 of CO.PDF).

It's possible that the doors inside your air paths are stuck. Heard a couple of people with that issue too - with the ignition ON (engine NOT running) and fan on speed 1, change the temperature from cold to hot and listen to the dash. Do you hear the doors moving? Try changing the air path from face to windscreen - do you hear the doors? There might be a need to dismantle the dash.