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View Full Version : Possible turbo issue? 4.2 diesel



Ricor
20th October 2025, 09:53 AM
So this is a first shot question.

I just purchased a 1996 Patrol with a 4.2l turbo. This is the first one I have driven.

It has 100km on it and is in very good condition. I have had it up on my lift and everything is tight and looks great except for some frame rust, to be addressed. Drives great, except for...

I don't expect it to be fast, and she drives and shifts fine, but she is slowwwwwwwwww. 0-70km/h is 21 seconds! When I am doing 80 and lightly punch it, she downshifts, and slows down for a couple seconds then slowly gains speed. I live on an island, so there is not much traffic, but I still hold people up every time I pull onto the main road. BUT, she starts immediately, is smooth as glass and sounds great. No turbo noise at all, ever.

My first thought is the turbo is not working, but I do not know what happens with them as I have never owned a turbo. I have built race cars, boats and everything in between, but never a turbo.

Your thoughts?

88882

Cuppa
20th October 2025, 10:38 AM
As purchased my '06 TD42i was a slug. Stock standard with just over 150k on the clock. The motors are very 'tuneable', but beware of overdoing it as it becomes a money pit, which increases the reliability these motors are known for. I had mine tuned 'for towing' on a dyno after fitting a 3"exhaust. The stock turbo pressure was only 7psi. Ours was increased to a max of 13.2 psi - less than many folk aim for, but just below what would require going down a rabbit hole of other upgrades. Doing this made it a different car to drive, what I believe it should have been off the factory floor. Not a speedster, but a very pleasant car to drive. In effect those changes gave it what felt like an extra gear, & the ability to hold a gear uphill. Those changes maintained the legendary reliability the motor is known for.

mudnut
20th October 2025, 11:33 AM
Welcome to the forum. Are you on Guam, by any chance? I do believe we have seen a pic of that same vehicle from the owner who transported it to the island maybe 1or 2 years ago.

Ricor
4th November 2025, 11:55 AM
No, I am in the US, Florida Keys.

Ricor
5th November 2025, 12:23 PM
Anyone else have any input on this? 25 seconds 0-60mph this morning. Again, smooth, sounds good but god so slow.

Cremulator
6th November 2025, 06:14 AM
Anyone else have any input on this? 25 seconds 0-60mph this morning. Again, smooth, sounds good but god so slow.The only thing I can think is to check the boost hoses and make sure they are connected properly and not split.
I drive an 04 GU TD42 turbo with a boost compensated fuel pump and I had an experience recently where my car was incredibly slow. Felt like it didn't have a turbo installed.
Turned out one of the boost hoses had come off a fixed metal line that is mounted to the top of the intake plenum and this was preventing the fuel pump operating correctly and limiting the boost the turbo was producing to about 5 psi.

Boost compensated fuel pumps are later models only, but the boost lines are definitely worth inspecting.

Ricor
9th November 2025, 10:06 AM
OK, I will look, thanks

Ricor
13th November 2025, 09:18 AM
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Ricor
16th November 2025, 10:32 PM
This is a repost from my post about fuel filter change, but it applies here:

SOLVED - probably

I moved on to change the gauze filter in the injection pump. It is so small it was hard to tell how dirty it was. Cleaned it with carb cleaner, it looked perfect and obviously was dirty. Reinstalled, and WOW. She pulled like a beast, and not pushing her very hard 0-60mph went from 39 seconds (post fuel filter change speed) to 15 seconds.

Will test the boost pressure this weekend but it is looking good.

Ricor
23rd November 2025, 04:54 AM
Installed the boost gauge and am getting 9lbs on a factory turbo. Runs like new. Such a simple little thing. Thanks everybody, including MudRunnerTD and geoffayres who really helped in a different post.