Engine lugging when shifting

[Bdang007]

Hi guys,
I've recently bought an ML 3.2 and it's been a bit of a nightmare. I've had some suspension issues but I will deal with that later on. Right now my main concern is my engine lugging, if I shifted from first to second whilst the car is under 20kmph it lugs, if I shift to third before 40kmph it lugs, if I shift to 4th before 60kmph it lugs! If the speed drops below any of those mentioned speeds and I'm in the wrong gear it lugs! What is going on? One mechanic thinks is gearbox issues, another thinks is injectors. I also blow a lot of smoke when accelerating hard. Any ideas? The pressure in my rail system is fine as it was recently tested, ive also had the manifold cleaned out and egr module installed.

[Geoff3DMN]

Has the car been fitted with larger than stock tyres?

That alters the effective gearing.

[Bdang007]

I don't believe the Tyres are bigger than standard but that is a very good point. If the tyres are bigger it wouldn't be significantly bigger as it looks very standard to me.

[Jeff Turner]

Bigger tyres yes can lug if pressure in them are incorrect . Also sweet spot in rev range. Find it. Yes mine can lug between gears.. I have mn 2013 with about 300 kg constant. Roof rack solar panel draws 2 extra batteries lol

[NowForThe5th]

These little engines are not the truck type of yesteryears. Power below 1500rpm is almost non-existent so, as mentioned above, you need to move up the rev range a bit to get to where you're still in the torque band when you shift up. Let it work in the 2000-3000rpm range where it's strong.

[Minza]

Keep the boost up to it and it'll love ya for it shouldn't lug then if in correct rev range like JT mentioned

[Bdang007]

Thanks guys, I'm not carrying anything and my rev range is between 2000-3000. When it lugs it violently shakes the whole car like it was an earth quake, I'm just not sure if this is normal... I've never had a another car did that to me before.

Could worn injectors cause something like that or gearbox as some of the mechanics have suggested?

[Bdang007]

When do you guys normall shift gears up as well as down (speed as well as revs) for normal daily driving not spirited driving?

I find it strange that I can't keep in 4th gear whilst going 55kmph, is that normal? If I was going at that speed and in 4th the car would lug and vibrate constantly until I'm over 60kmph or until I dropped to 3rd.

[NowForThe5th]

Yeah, you're right, that type of shaking is definitely not normal.

I'd start with the obvious things like some problem in the engine/gearbox mounts, driveshafts, centre bearing and then work your way back. Busted clutch can give similar symptoms. Not discounting engine or gearbox but look at the other things first.

[Bdang007]

Thanks Chris, good points, it might not be engine mounts because I think it would vibrate even when the car is not moving (which it doesn't).
Also when it lugs, I basically have zero power and usually would have to down shift. If I was going at 40kmph and I was in 4th it feels like it's about to stall on me and it will not accelerate.
I was thinking it could be a cluTch issue even though it was changed only 2 years ago. This is a big mystery but I don't want to go to a mechanic without some ideas of what it could be so thanks for the suggestions.

[RHKTriton]

Check out the SCV.

Last couple of days has provided some surging - felt like the prop shaft was made of rubber.

After observing rail pressure and boost during the usual driving I observed the rail pressure drop really low just when I needed to accelerate. Then it'd bounce back to normal once up to speed.

Today all is running normal again.

At the moment I put it down to a bit of muck jamming the plunger in the SCV and that has now either broken down or worked its way through it.

Other items worth checking are the swirl flap mechanism and the MAP hose isn't blocked.

[Bdang007]

I've recently cleaned the MAF sensor and it's improved the smoke situation a little but the lugging is still very evident, next will be the SCV. I'm not sure how I can check the swirl flap mechanism, would it involve taking off the intake manifold?

How would you know if your clutch was going? If the lugging was caused by the clutch, would that mean the clutch would have to be quite deteriorated? My clutch friction point seems to be near the end so I think it's worked out but besides that I haven't had any other issues.

[Bdang007]

Check out the SCV.

Last couple of days has provided some surging - felt like the prop shaft was made of rubber.

After observing rail pressure and boost during the usual driving I observed the rail pressure drop really low just when I needed to accelerate. Then it'd bounce back to normal once up to speed.

Today all is running normal again.

At the moment I put it down to a bit of muck jamming the plunger in the SCV and that has now either broken down or worked its way through it.

Other items worth checking are the swirl flap mechanism and the MAP hose isn't blocked.

Quick question, how did you actually observed the rail pressure?

[RHKTriton]

I just use a BT dongle and Torque Pro app on my Android phone.

You can set up any combination of gauges, in this case I had set up Rail pressure, coolant temp, EGR & Throttle as well as Boost.

[Bdang007]

Ah yeh I got one of them dongles, but I'm only using the free version of torque. Maybe that's why I can't see the fuel pressure, I think you might be right in relations to the scv. I've ordered one and now just waiting for it to come over from the U.K. So it's gonna be awhile. Thanks for the suggestions!

[Bdang007]

Update: just changed the SCV but it made little to no difference
I've been using cost effective maintenance fuel additive and it's made it smoke a lot less but besides that, the lugging still continues.

Might have to find some time to get it to the mechanics I think.

[RHKTriton]

Have you checked the swirl flaps mechanism yet.

I found overall that the engine runs better with this disabled - got two inlet ports, might as well use them.

[Bdang007]

I'm not sure how to check the swirl flaps,or how i would disable them?

I've taken it to the mechanics and he said most likely some mount issues that's causing the vibrations at low RPMs. Some sort of harmonic frequency that causes everything to vibrate, might be quite difficult to diagnose where it is actually coming from... =(

[ag9111]

A stuffed mount will not cause lose of power.
What rpm are you talking about when you mention your speeds.

[MilkmanDan]

What part of the world are you in, might pay to see if another member can catch up to compare vehicles

[Bdang007]

A stuffed mount will not cause lose of power.
What rpm are you talking about when you mention your speeds.

I agree.

the shudder happens below 2000 rpm. Once past 2000 rpm it's fine. It shudders most for 3rd gear just under 40kph.