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-   -   Car Launch/Hesitation Problem (https://www.team-bhp.com/forum/technical-stuff/27616-car-launch-hesitation-problem.html)

Hi,

Refer my ride in my signature.

Here are some stats measured thru VAG before I get into the problem.

Original RPM - 760; modded through VAG - 810
Lambda (LTFT) - (-17%),(-16%)
Fuel Used - Shell Super Unleaded
O2 sensor primary voltage - 0.453v @ idle (almost perfect 14:1)
No error codes

Now, when I acelerate the car from idle, for example raise it and launch I should typical get wheel spins imho. But the car kinda misses a beat and gives out a funny sound, hesitates a bt and then accelerates, I kinda need to adjust using clutch and accel combination to compensate. This is a bit more pronounced with A/C on, I think.
Also, if I do manage wheelspins sometime - its kinda delayed, like there is a significant lag for the power to get transferred to wheels, hesitation and the lurch and then revs happily.

Not sure what the problem is but is kinda irritating in traffic etc., also specially when I want to spin my tyres just a bit...:p

Any thoughts anyone on what the problem could be?

Thanks,

Your clutch could be slipping - wheelspinning, the cause

But if the case is of clutch slip, the RPM should also rise I guess - this is not happening; RPM rises drops a bit and then accelerates... ???

from your signature your have lot of goodies, somehow it aint properly syncing .. VAG can be the prob or you have set it up that the power band has moved up lil too high.

ps: where did u source the magnaflow from?

I also thought of fouling but not sure how that could happen. If I had more air I wouldnt be running with -17% Lambda.. which negates the issue on the movement of powerband too imho.

Magnaflow thru JD @ Chennai.

-Maybe I should explain the RPM not rising bit , it does rise till I rev with clutch engaged, but does not kinda respond momentarily or RPM drops when I disengage followed by the hesitation and funny missing beat sound.... then a couple of secs everything is alright and accelaration sets in.

BTW, my clutch is not "dual mass flywheel"... it is the ordinary single one.

It looks like a drive shaft issue to me.

Drifter

Could you please explain how a drive shaft could cause an issue like the one I have described?

mayb your fuel injectors are clogged. when you put your foot down they're not able to deliver the required amount of fuel in sudden bursts.

could also be a worn out clutch. hard to say.

Injectors - no way. Inspected them - clean and shiny! Plus if it is a problem no way the Lambda would not be -ve.

When you say worn out clutch - did you mean the plate? BTW, my car is about 26k+ only on the odo. Any other tell tale symptoms that I should check for?

Hi,

Its definitely not a drive shaft problem. I would suspect the fuel filter, throttle body, air filter or injectors in the respective order. Could also be a faulty cam sensor.

Viper

Fuel filter – not checked – will check – just trying to think how it could be an issue if Lambda is already @ 15+% - which means fuel supply is adequate. Only thing I can think is fuel is not supplied instantaneously
Injectors – clean as hell
Throttle body – cleaned up recently
K&N – cleaned up about 1k kms back
Cam sensor – how could that be an issue?

At idle you're running 14:1? You have fuel management issues.

Get your Sparkplugs checked for fouling, your ignition components Coils/wires etc.

agreed..dude
if your injector was clogged, ur LTFT would increase

you mentioned you are not pulling any DTC's ..
ok, maybe the parameters have not yet triggered a code as yet, how long have you been having this issue ? how many drive cycles ... ?

can u check ur ignition timing values during this initial accelaraton ?
Are u getting -ve/+ve TDC values etc ...
just want to check if ur ECU is not cutting off power by excessively retarding ur timing .. possibly as a pecautionary measure

are you going WOT during these accelaration runs ?
also let me know what ur regular sedate part throttle and WOT advance/retard values..

also does this erratic behaviour happen when ur engine is hot or even when it is cold ? check ur ECT values and let me know ...

Hi,

Have you tryed cleaning Throttle body and alignment?????

PJ