Acceleration Dip

Posts specific to the 2.5 litre turbo engine

Acceleration Dip

Postby KS487 » Sun Aug 26, 2018 10:04 am

I've noticed this weird issue in my 2008 Liberty GT Spec B. Sometimes at full throttle it feels like a big torque dip at around 4K RPM and then it picks back up and the car slingshots off again. I've noticed it in 2nd gear and sometimes 3rd gear. I've also noticed it every now and then at around 3-3.5K at like 1/2 or 3/4 throttle (I avoid going full throttle below 3K). Has anyone else experiemced this? Or know what it could be?

I've been thinking about getting a tune done recently for other reasons (mainly to get rid of crap factory tune and get a bit more oomph). Could a tune rectify this?
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Car: 2008 Liberty GT Spec B 6MT

Re: Acceleration Dip

Postby norbs » Sun Aug 26, 2018 10:50 am

Could be something pulling timing due to an issue. You really need to get it logged. Check things like IAM A/F Learning and Fine Learning Knock Correction tables. Also, check boost pressure at around those load/RPMs. Could there be a leak?? Poor fuel?? Dirty MAF? Dirty injectors? Clogged CAT? List goes on. Point is, don't get it tuned until you have rectified the issue otherwise you'll be pissing money into the wind.

Hook up with a member who has logging tools.
'05 Lib GT with a few mods :-)
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Re: Acceleration Dip

Postby fedaykin » Mon Aug 27, 2018 11:53 am

When was the last time you changed the spark plugs?
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Re: Acceleration Dip

Postby natho » Mon Aug 27, 2018 3:05 pm

mine has done that from either pinging or overboosting. in my case they were both related to a kink in the wastegate hose.

a little hard to tell without some datalogging.
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Car: 07 Liberty GT

Re: Acceleration Dip

Postby KS487 » Sun Sep 09, 2018 4:59 pm

Hey guys,
Thanks for the advice! What would be the best approach to data logging? The engine has been running pretty happy under load and the issue hasn't come up again since I created this thread. This is a good thing but also annoying at the same time because my concern is that I'll plug in some data logging tools but I won't be able to replicate the issue.

The spark plugs is a good thought though. I haven't changed them since I bought the car so I might give that a go!
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Joined: Wed Apr 05, 2017 8:22 pm
Car: 2008 Liberty GT Spec B 6MT

Re: Acceleration Dip

Postby Vontisch » Thu Oct 11, 2018 7:59 pm

I have got this exact issue with my 07 GT-B. It has only started since I replaced my MAF. The MAF was faulty and threw a code. Since replacing it this is now my happening. 2nd 3rd 4th gears with anything over 50% throttle or under load. Gets to about 2.5 and 4K then fails.

I am due to have my plugs done and a recall with the fuel pump harness connector.

It has never missed a beat since the issue with the MAF.
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Re: Acceleration Dip

Postby bigBADbenny » Wed Oct 24, 2018 3:00 pm

Log the avcs vvt angles, per cylinder misfires, as well.
Tactrix, Btssm or vagcom with android or pc is the easiest approach for full ssm logging.

Heaps of info here, lmk if you need links etc.

If its too hard, your tuner might be able to diagnose but consider the extra expense over diy.
Once you have logs, diagnosis is possible.
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