HDJ79R Engine surges while coasting. Is this Normal ?

[wal4x4]

Hi Guys, Just picked up a HDJ79R tray (factory turbo) 190,000kms completely stock. I noticed driving home last night when I hold my foot in a constant position, at any speed I get a surging feel, kind of like cruise control cutting in and out but it happens every few seconds. I don't have cruise fitted so I know it's not that. I don't know anyone with one of these so i just wanted to know if it's normal?

Any info is welcomed.

Cheers, Wally.

[mickbeny]

Hi all...Thats definately not normal.

[wal4x4]

Hmm Thanks for that. The surge is ever so gental you hear it more than feeling it. It's hard to describe the rise and fall in RPM is about 100-200 RPM so not alot. Doe it in all gears when just resting your foot in the same spot and on a flat surface. When you accelerate it disappears.

[tweak'e]

one basic thing you can check is oil in the intake tubes. could be leaking from turbo or just out of the breather especially if its overfilled with oil.

[wal4x4]

Had a look around the engine bay yesterday afternoon. I found 2 very lose nuts on the intake manifold at the front of the motor. Also on the intake crossover pipe theres a vaccuum module the small rubber hose was lose, Ive done up the nuts and pushed the hose on further. I'm giving it a run today to see if thats sorted it out. It has a exhaust leak too where the turbo dump pipe joins to the the Cat. Looks like to bolts with springs and a flange it leaks between the join.

Thanks for your help guys.

[wal4x4]

No good still has the slight surge. I checked for oil in the intake pipes there was only a tiny film inside. Could it be the throttle sensor?

[wal4x4]

Got it sorted out at Turbo Engineering in Thomastown, had a diagnostics check ($260) there were a number of issues they sorted out for me. While it was there I had it chipped. It goes very hard indeed, I have since added a 3" straight through exhaust. I didn't realise these things hammer with chip and exhaust. 130kw at the wheels and 695NM according to the dyno report.

Thanks for your help guys.