Nm35 Vq25Det Excessive Fuel Smoke:-/

[brizzi]

Hi there I don't know much about vq25 engines as all I have owned are rb engines in the past. I have a problem with excessive black exhaust smoke.. At stone cold idle , then the first throttle to get up my steep driveway. Normal driving smells a little rich, but on boost or mid to hard throttle it bellows out! Visible in rear view mirror, and it smells like rotten egg.. It's doing my head in and it's embarrassing as it's a great car as a daily to work all my work mates complain about following me while leaving work.. I don't want to start replacing parts that don't need replacing any help much appreciated :-)

[joshm35]

May just need to be tuned. So like me may need a aftermarket piggy back ecu then put it in to be dyno and tuned

[Brick]

Have you modified the car in anyway? I found mine started running very rich after I started modding the car.

[scotty nm35]

When did you change the plugs last?

What mods have you done, as Brick mentioned?

Perhaps you have a boost leak? I would try pressure testing the intake.

[Ben C34]

Boost leak. Always boost leak.

Every time.

Most of the time.

[brizzi]

Hifow turbo, big dump pipe, 3 inch exhaust, hi flow cat, front mount, big stainless turbo intake, upgrade fuel pump 1 bar boost. Stock ecu. Cleaned afm with Electra clean plugs are new gapped at .9 Checked all intercooler pipes etc no visable leaks. Great fuel economy has me baffled :-/

[brizzi]

Can you put one of those safc neo fuel trimming things on it to adjust fuel a bit? Had one on my old series one c34. Do they work on these v6 vqs..

[Ben C34]

Looking for leaks is not the same as pressure testing for leaks.

You must pressure test.

[Daleo]

I also have a steep driveway; and stone cold, first thing; if I reverse up to put on my trailer, mine will also give a cloud of black smoke.

The clouds of smoke on mid throttle/boost definitely sounds like a boost leak somewhere.
Another member chased a very similar issue for months, and eventually traced it to a split intercooler pipe; it could only be seen once he removed the pipe completely.
Time for some pressure testing.

Good luck with it.

[brizzi]

Thanks for all the input fellas:-) went through and replaced all crap hose clamps with t bolt ones... Car drives heaps better even has more vacuum at idle on factory boost gauge :-) Now to get rid of blitz bov as I still get a hint of smoke lifting off the throttle..

[scotty nm35]

Now to get rid of blitz bov as I still get a hint of smoke lifting off the throttle..

That will do it...

I just helped tune another M35 running stock injectors with an emanage, it was running higher boost using my modified actuator. We found there was 25% more fuel being injected in the midrange than it needed, due to the stock computer dumping fuel and timing. If you start bumping up the boost the ECU will protect the engine...

It was probably making less power than stock and the economy was woeful. Anyone modifying these needs some way of tuning the excess fuel out.