TD42Ti "engine noise"

[dasemm]

Hi all, I have an issue with my GU4 TD42Ti. Was cruising along no problem, stopped for some food, got on our way again and me and the missus noticed some "interference" (well that's what we thought it was). So after turning electrical stuff of, and winding down the windows, it was coming from the engine bay.
So long story short, when I accelerate at a moderate level I hear a misfiring or leaky exhaust gasket sound, and under no load it starts around 2500 RPM, and I also seem to be a bit low on power when it occurs. Engine starts as normal, idles like it should, just under medium load and above 2500 RPM i get the noise and low power.

I don't have pyro/boost gauges yet (ordering from eBay now), and the noise sounds like it is on the intake manifold side.

I have changed air/fuel filters, checked for a mesh filter under the banjo bolt (none in mine), checked for a leaky exhaust gasket, checked the waste gate that it opens/closes and waste gate actuator. I have also tested some of the ECU voltages, throttle sensor, timing control voltages, throttle.egr solenoids. Still cannot find anything with my limited engine knowledge.

I am going to book it in with a mechanic on Monday, but I hate not knowing what the issues is.

Any help appreciated... oh, and this forum was really good in assisting my troubleshooting..

Darren

[YNOT]

Without hearing the noise it's very hard to say for sure. From your description I would suspect a exhaust leak somewhere before the turbo which would explain the lack of power as well. It could also be the over boost pressure relief valve on the inlet manifold (see pic), if the spring has lost tension the valve may be venting at lower than normal pressure.

Tony

[dasemm]

thanks for that Tony, will have another look..

[guterra]

Ah HA!!!! Grenaded 4.2!!! Let's start a conspiracy about 4.2s blowing up just like the zd's...

No just kidden mate, I too know what it's like not knowing what the issue is... Except mine is a grenade...

Good luck and hope it ain't to costly

[timbar]

i would be checkking exhaust manifold they like to blow out the gasket usually cylinders 1 and 6 in my experiance

[dasemm]

ok, will have another look. would I expect to see black/sooty marks around a leak ?

[YNOT]

ok, will have another look. would I expect to see black/sooty marks around a leak ?

Possibly depending on how big the leak is. Have a listen around the exhaust while someone cracks the throttle open for you, see if you can track it down that way. A short length of garden hose held to your ear makes a great stethascope for this sort of problem.

Tony

[Wizard52]

Had similar experience with my GUIV. The vacumn hose? going to after market relief valve near turbo had a split where it goes on to the pipe. A sharp knife and a cable tie fixed it. Obviously I'm not a mechanic to know proper names of bits here and there. cheers

[dasemm]

yeah, pretty sure that part of the system is OK, I have checked for leaks, but not really sure at what PSI the actuator is working at. I am waiting for an ECU talk cable to see if the engine is putting up any codes.. should hopefully arrive today.

[dasemm]

well I have hooked up ECU Talk, taken it for a bit of a run and seem to be getting fault code 43 - throttle position sensor errors, I also noticed that one of the gauges Inj Timing C/V % goes close to 0 when the noise occurs, this needle is all over the place when under load or higher revs. Could it possibly mean that the timing is retarded ? could explain low power and a lack of black smoke from the exhaust..

I have also taken tony's advice with the hose to the manifold and cannot hear any difference from the pistons..