Y30DT - misfire/stumble/hesitation etc, etc..

[gtr1000]

One for the 3.0V6 diesel gurus......

Call it what you like, but the misfire on these engines seems to have been discussed many times but mine seems to buck the trend.

The misfire I'm getting only ever happens at a specific throttle opening, ie. when the accelerator is in a certain position and only on very light throttle openings. The misfire is there irrespective of rpm's, speed or engine load. It won't exhibit the fault if the engine's revved with the car stationary.

I've had it connected to Tech-2 and Op-Com and no faults or error codes have been flagged up.

So I'm thinking maybe the throttle position sensor (TPS) is acting up and IIRC, there's a sensor on the pedal itself but is there one in the engine bay as per all other VX diesels?

Your thoughts and solutions (?) would be most welcome .

[Critch]

Can you see what voltage readings your getting from the sensor at various positions?
Ie no throttle. Part throttle an full throttle?

Could maybe try taking the throttle body off and ensuring the butterfly is free and giving it a clean with some carb cleaner?

[gtr1000]

When it comes to car electrics, I've not a clue. I wouldn't know at which end to measure the voltage or indeed what volts it should be.

Throttle body - yep, tried that but I'm still not sure what the TB and flap inside actually do on a diesel. I know it's purpose on a petrol engine is to regulate the air flow but this ain't the case in a diesel - the air's fixed and the fuel varies.

[Innes]

With op-com or tech 2 you can see what reading the sensor is giving out i.e. you put your foot half way down it'll show 50%. Slowly press down the throttle down and see if the % climbs with it.

[Critch]

I'm not sure on exact figures. Someone maybe to confirm. But the figures on trucks I work on. So can't be to far different. Are no throttle 0.5v part 1.0v full 4v

If you can get op com etc live data readings may help. See what's happening. It should give voltage readings and stuff aswel save hassle of trying to get on pins etc.

It acts pretty much same way. Regulates the amount of air into the inlet.
The fuel an air then mix in the combustion chamber once fuel is injected.


Have you checked all fuel lines. And fuel filter? If you listen through a screw driver on each injector do they all sound similar?

[Celes]

If anyone solves this issue I will praise them as gods.

I've come to think it might be a CV-joint problem and not really engine related. I doubt it's a duff DMF causing this as I've driven an automatic with the same problem.

[gtr1000]

Should have mentioned that the car's a 54 plate with 46k miles.

Fuel lines look good and the engine's easy to start after it's been standing overnight so probably not an air/fuel leak issue. Fuel filter changed last week, 10k Boost through it at the weekend and has showed a slight improvement.

All the injectors sound the same at idle but let's not foget that the misfire only occurs when under way at small throttle openings at no specific rpm or speed, so for that reason alone I don't feel it's a driveline problem. And I can't listen to the injectors on the move .

I guess to check the TPS voltages, the engine doesn't have to be running and would a dodgy TPS show up anyway, bearing in mind I have no spanner light or fault codes?

I really need to get live data readings which means coaxing my local mechanic into loaning me his Op-Com .

So there's a TPS switch on the accelerator pedal but what about the other end under the bonnet?

[Critch]

We're about are you mate someone on hear might be able to help.

[Celes]

I replaced my injectors in February, and noticed little to no change in noise (of each cylinder/injector) so I'm inclined to think I have an electrical problem.

I got hold of a Steinbauer power box worth 1 grand - you plug it in between each injector. This pbox also has a reference (what is that anyway?) cable which reinterprets the signals coming from the TPS, so in theory this should make a difference (if the TPS is causing the judder).

[gtr1000]

I got hold of a Steinbauer power box worth 1 grand - you plug it in between each injector. This pbox also has a reference (what is that anyway?) cable which reinterprets the signals coming from the TPS, so in theory this should make a difference (if the TPS is causing the judder).

When you going to plug it in and let us know the results on the TPS?

Tomorrow?