Boost gauge question + running problems

[Oddball Matt]

Hi guys got some minor hiccups with the truck, it's a '99 terrano 2 2.7L diesel automatic, here's a shortlist of what I'm trying to solve:

-The engine is idling roughly, or rather jumping thr revs up and down. In fact when it's idling it sounds as if it's saying bruh...bruh...bruh...bruh... If you catch the engine on the wrong spot of the wave when giving throttle it dies on the spot, usually when going from reverse to drive.

-Part throttle does more or less the same, the engine sound is going awwawwawwaww. Full belt it runs fine.

...unless...

Sometimes the turbo doesn't engage, usuallu when hot and having done lots of stopping and going, the engine is totally gutless barely having enough power to accelerate but forget climbing any hills. After standing and cooling for a few minutes it's working fine again so I'm suspecting a sticky wastegate actuator. I took the intake tube off to have a peek at the impeller, it's sooty black on the intake side but not drenched in oil.

To combat the rough running I have run a tank full spiked up with STP COMPLETE FUEL SYSTEM CLEANER FOR DIESELS, it did help but not completely remove the problem.

To have an understanding what the turbo is doing I'm fitting a boost gauge over the weekend but would like to ask where have you tapped in to get a reading? I've seen someone do it off the intercooler side at the top, I checked and even though the hole is threaded it's not drilled through and I'd rather not remove it to do it so I was thinking would the small 90° bend going to the wastegate actuator be a good place to tap in?

One more thing, the turbo on mine is loud, and I mean LOUD! Or rather not the turbo itself but when on boost I'm getting this ear piercingly loud high pitch whistle, do you reckon this could be a pinhead leak somewhere?

Still reading? Thanks, any answers to any of this highly appreciated.

 

[solarman216]

Unlikely to be a stuck waste gate, they rarely open on these motors if at all, from your description I would say the turbo is goosed, stick a tee in the actuator pipe and connect your gauge to that, Rick

 

[Oddball Matt]

Interesting because since I'm a mailman I drive and especially accelerate with the window down a lot and I'll swear I can hear the signature sigh of a wastegate almost every day.

Fitting the meter and doing some rounds to get more data, also planning to gopro the actuator shaft to see if it's moving, really hoping it's not the turbo as a new one seems to be over six hundred and I got a heap of big bills waiting!

 

[Goatmaster]

Unlikely to be a stuck waste gate, they rarely open on these motors if at all.

So a bleed off valve would be a waste of time? I've used them before on diesel Merc engines with good results but would it likely cause problems on a 2.7 Terrano by confusing the ECU?

 

[Oddball Matt]

Alright gauges fitted and some answers found.

First off I found out what is causing the hellish whistle on boost, as well as (at least to a point) the jumping idle. There was a gaping hole in the exhaust :doh :lol To my defense I've had two of these trucks, the first one had a very loud modified side exit exhaust, and this one's been like this since I bought it last December so I've never known what it's "supposed" to sound like The hole was pointing upwards at the downpipe-flex joint seam so wasn't easy to find but it's all sealed up now.

Next question is how much boost are these things supposed to make? Mine seems to top out at around 0.6-0.7bar which seems a bit low to me.

 

[solarman216]

10 to 11 psi is about right for a stock 2.7 Rick

 

[Oddball Matt]

Ok thanks I remember reading somewhere the factory boost pressure should be around 1.3bar which is around 18-19psi, so either that was a load of malarkey or I understood sth wrong

 

[solarman216]

IIRC when I tested one of mine the waste gate opens at around 12 to 13 psi but the turbo never managed to do it, I have an old turbo in the workshop so will give it a test tomorrow, to confirm, Rick

 

[Goatmaster]

It appears the TDI engine will only take about 12 PSI before the ECU initiates limp mode.
18 PSI Max before danger of destruction
https://www.offroadexpress.kiwi/Forums/viewtopic.php?t=20868

Page 3 Crash Bandicoot's comment.

 

[Oddball Matt]

So a couple days worth of data collected and I'm pretty sure the problem is not the turbo after all as the meter is showing consistent values of boost all the time. I've searched the internet and it seems the english term of what I'm experiencing is called hunting idle, though most cases I've found have had a more rapid hunt whereas mine is about one surge per second. It is getting worse though and the engine is starting to die more when coming off idle so I'm beginning to suspect I either have an intake leak, or the engine is getting insufficient fuel. Swapping the fuel filter next, it's been changed last winter due to water contamination but it's probly the cheapest thing to start with. I also have a can of leak finder spray so gonna play with that to see if I can find something.

 

[solarman216]

Your problem could well be the pressure regulating valve (this was commonly referred to as the mini filter, which was a misconception on these motors) it is an easy fix but does require removal of some pipes and a rather odd spanner which you may or may not need depending on your particular pump, basically two parts that need a clean up, there are some you tube vids on the subject, Rick