Faulty centre diff causing power dips and hesitation?
 

Hi all. I have a Hawk STI with and intermittent hesitation and stumble which is think might be related to the centre diff. I've experience it a few times now, maybe 10 or so and it's like the power delivery drops off and the car stumbles 2 times in very quick succession then goes back to normal. It seems to happen under the following conditions;

- just after the diff has been worked hard, like accelerating off a large roundabout or at a junction with some rear or 4 wheel slip on the turn. It does not seem to happen in straight line or standing start accel
- full or mostly full throttle accel
- just after the gear shift (1-->2 or 2-->3 usually) as the I put the power back on
- when the diff is set to auto mode, not in manual unlocked mode

The car had some new tyres and wheel alignment done recently, although I don't think they did a good job because the steering wheel is off to the left in straight line driving.

Has anyone experienced anything similar?

"Car had some new tyres" they should be replaced in pairs or idealy all 4 with same brand of tyre but dont think thats your problem as that can only cause clunking and binding of the steering sounds more engine related.

hi jay, by "some" i mean new tyres all round, Goodyear eagle f1s

How much fuel is in the car when its doing this, do you run the car quite low?

any amount, i usually fill it up when it's 1/4 left and with shell v power (or nearest 97 ron fuel), so I don't think it's fuel starvation. the odd thing is that it happens just after gear change and putting the power back on, usually with slight steering wheel angle still applied, and also it seems only in Auto diff mode. today i drove the same route in manual unlocked mode (green indicator at the bottom) and it didn't do it. The other thing is that it's always 2 dips in power in very quick succession, almost like i'm changing gear just as the diff is recovering/locking from whatever it was doing to balance the torque front/rear

It's highly unlikely to be the diff causing issues you're describing.
Im putting my money on fuel surge. I can get surge with over half a tank.
Do you have any warning lights on the dash?
Have you performed dccd diagnostics test? Have you had dccd in test mode?

I doubt it, I'd say fuel cut caused by 97 Ron fuel.

it does it running on v-power also. there are no lights on now or during and no DTCs that I can see with a bluetooth OBD tool and Torque for android phone.

How do I do dccd diag and test?

The car has 67k on the clock with an engine rebuild @ 61k. Not sure when or if the fuel filter has been replaced, so this might be worth a look? Do you know where it is and how to change it on a hawk?

Cheers!

Guys he said that on manual fully open on Dccd it don't do it, but does on auto so hence front diff related.
It does sound like something when in auto you floor it and it moves lock to more forward but like there's something worn and needs time to catch cog or whatever.

I don't have auto, just leave in fully open, no noise/clunks etc and with more lock is horrible when meneouvering etc.

Could well maybe it's been left in auto all its life? And aren't you supposed to keep it open unless slippery surface?

What only when coming out of corners. Anyway fuel cut takes reference from manifold air pressure not fuel quality.

The dccd diagnostic procedure has been posted many times before but if the diff open light is not blinking then there are no faults with it.
Fuel cut usually happens when you decat your car and don't map it because there's less back pressure in the exhaust causes the turbo to overboost.
It tends to happen more in higher gears so stick it in 5th and Rev it out to 5k and if it doesn't do it then it's not fuel cut.

What are you on about? Fuel cut will happen when it dets too as that's what the knock sensor is for....

I'm afraid you're wrong there chum the knock sensor Can affect timing it can not induce fuel cut. And what Im on about is the OP said it happens when coming out of a corner.... Do you think it's possible to have a car that fuel cuts in that situation but not in a straight line or are you just the argumentative type.

Hey you obviously know more than me mate...!

I agree about coming out of corners not been fuel cut, however fuel starvation is definitely possible, will feel the same.

ok, so following the questions and debate about fuel starvation and/or cut i did some testing today. The normal section of road where it occurs (which I drive daily) is a large 3 lane roundabout between two 70mph dual carriageways so you can come in hot, stay hot, and exit pretty hot to. I filled the car with to the brim with v-power, my findings are:


- does not occur in standing start or straight line accel, with dccd in auto or manual fully unlocked (green indicator down). i did not test fully 'locked' maybe I will do this tomorrow

DCCD in Auto
- occurs when exiting the roundabout in 2nd gear after rear/front slide then changing up gear as you are left steering and entering the dual carriageway. the double stumble occurs just after you push back on the power following the gear change
- does not occur under the same conditions as above but not changing gear


DCCD in manual fully 'unlocked' mode
- does not occur with or without gear change


DCCD in fully 'locked' mode
- TBC

I’m wondering if there is some software that I could use to monitor and log the lock condition of the front diff, but Torque for Android does not seem to have this function. Can anyone suggest one that does?

Hello there mate did you get to the bottom of your problem?

hi, not deliberately fixed, but is now, I've changed a lot of things on the car, fuel pump & filter being some, and as was mentioned previously most likely it was some odd fueling issue.