Troubleshooting power loss

vanvanvan · Post by **vanvanvan** » Tue Aug 14, 2018 3:12 pm

Got an interesting one here. 92 L300, diesel.

Just replaced my turbo. Van runs, but is struggling power-wise on the low end. It can get up to and move at highway speeds, but it's struggling at the low end. Acceleration is slow, the transmission doesn't seem to want to downshift and the gas pedal just feels ineffective. Additionally, I've noticed my speedometer needle wiggles/shakes up and down a bit as I accelerate.

Any thoughts on how you'd go about troubleshooting this, or any rough ideas what could be going on?

sk66 · Post by **sk66** » Wed Aug 15, 2018 7:37 am

Did you replace the turbo with a like model? Are you building any boost pressure at low RPM?

deli cinq · Post by **deli cinq** » Wed Aug 15, 2018 12:45 pm

when the mechanic shop changed my turbo the waste gate was backwards to the original turbo. and my old turbo made 10psi

Post by **Growlerbearnz** » Wed Aug 15, 2018 2:13 pm

How much boost does your new turbo make?

vanvanvan · Post by **vanvanvan** » Fri Aug 17, 2018 9:05 am

I don't have a boost gauge, so not sure what psi I'm generating.

Hmm.

Post by **Growlerbearnz** » Fri Aug 17, 2018 2:43 pm

That's your step 1 then. Get a boost gauge (even if you just install it temporarily) and see how much boost you're making. It should be around 10psi at 2000rpm when accelerating hard. If it's too low, then the mechanic has probably set up the wastegate actuator incorrectly. If they had to modify the turbo to make it work with your old actuator, then it might need some fine tuning to make it work like a factory setup. I'd be disappointed if a mechanic installed a new turbo, especially one that was different to the old one, and didn't test that it worked before handing the vehicle back.

The wiggling speedo needle is unrelated, though it might have started when the engine work was done if the speedo cable was moved. It should be routed so it's as smooth as possible, with no tight bends. If the wiggle has always been there, it's more likely just a lack of lubrication.

Fix the engine first though.

sk66 · Post by **sk66** » Fri Aug 17, 2018 9:06 pm

I'm guessing the issue is the new turbo install... especially if a large airflow version (high rpm, gas engine) version was installed. There are a lot of TD04 variants and they can be quite different in performance characteristics. If you just went with "it fits" aftermarket version it could be the same kind of issue.
A poorly adjusted waste gate actuator would be the first (easiest) thing to check though...

sk66 · Post by **sk66** » Fri Aug 17, 2018 9:08 pm

deli cinq wrote:when the mechanic shop changed my turbo the waste gate was backwards to the original turbo. and my old turbo made 10psi

I'm a little confused by this post...

Post by **Growlerbearnz** » Fri Aug 17, 2018 9:18 pm

I'm guessing it was a 4D56 TD04 from a Pajero or L200. They have the wastegate actuator down low, mounted to a bracket on the turbo itself, with the actuator rod horizontal. Which means the little wastegate lever on the turbo is oriented the wrong way and has to be modified (bent) to work with our vertically-oriented actuator rod. Here's one when viewed from above:

: td04-4-4(22)-800x800.jpg (34.51 KiB) Viewed 6936 times

Not sure how we know it was making 10psi without a boost gauge though. I'm guessing the mechanic tested it before replacing it.

vanvanvan · Post by **vanvanvan** » Mon Aug 20, 2018 11:21 am

Appreciate the responses.

My mechanic suggested I replace the fuel filter for starts. I was skeptical that this was the culprit, given that the turbo had just been replaced and the loss felt significant. However, it does make a bit of sense. The filter hadn't been changed in at least 18 months, the Delica sat in my driveway for about 2 weeks without driving, etc.

So I changed the filter and noticed a considerable improvement. I'd say I'm about 70% back to the power I'd experienced prior to replacing the turbo. I do feel the turbo a bit more now, esp. on the higher end of course, but I'd still say I'm struggling for a little low end power. I do find that my transmission is a) taking a bit longer to shift than usual and b) not downshifting as readily. I may need a fluid change there, as well, unless that could somehow be explained by a mal-adjusted turbo..I don't think so..

Anyway. Progress. Boost gauge, EGT, and turbo timer in the works, in addition to taking the van back to him to investigate a bit more.

Post by **Growlerbearnz** » Mon Aug 20, 2018 5:02 pm

Check the technical reference library for the post about adjusting/correcting the kickdown cable- it's possible your mechanic altered its adjustment when doing other things on the injection pump. Kickdown is entirely controlled by accelerator pedal position, so a drop in engine power output shouldn't alter when the transmission changes gear.

vanvanvan · Post by **vanvanvan** » Thu Aug 23, 2018 7:39 am

Growlerbearnz wrote:Check the technical reference library for the post about adjusting/correcting the kickdown cable- it's possible your mechanic altered its adjustment when doing other things on the injection pump. Kickdown is entirely controlled by accelerator pedal position, so a drop in engine power output shouldn't alter when the transmission changes gear.

Yep - that did it! Much appreciated. I was starting to suspect it was something along those lines. It's adjusted about as far at it can be in order to reach the correct measurement, which seems to mean I'll likely be due for a new cable soon.

vanvanvan · Post by **vanvanvan** » Tue Aug 28, 2018 11:40 am

Ok - so I’m not totally convinced that I don’t have a power loss and that the problem was totally a stretched/maladjusted cable..

Yes, around town driving is just fine. Feels normal. But mountain passes (that I’d previously done just fine on) are now a bit of a struggle. Getting passed by RVs, slowly losing speed regardless of pedal position. Turning overdrive off helps, but I didn’t have to do that in the past.

Going to have my mechanic take a look. He’s installing a boost gauge too, so perhaps that’ll shed some light.