Big jerk while accelerating

allllec · Apr 20th, 2011, 19:29

Hi there,

Just seeing if anyone has come across this.

If I floor my T5 auto occasionally there will be a massive jerk at a random point in the revs. (Feels like I've jammed on the brakes for 1 second)

Feels like a really violent spark/fuel cut however the car is not over-boosting and I have no lambda lights etc.

Anyone had this before?

Kind Regards

Alec

The Hooded Claw · Apr 20th, 2011, 19:45

My Mrs read your Thread Title & thought you were talkin about ME drivin too fast (AGAIN!!) LOL!!!

Claymore · Apr 20th, 2011, 20:24

sounds like your hitting boost cut, have you got an mbc on it?

Luxobarge · Apr 20th, 2011, 20:56

Quote:

Originally Posted by The Hooded Claw

My Mrs read your Thread Title & thought you were talkin about ME drivin too fast (AGAIN!!) LOL!!!

Lol. I read the title and thought "Yeah, so am I....."

Sorry to hijack thread, wish I could help but not had that problem.

allllec · Apr 21st, 2011, 00:05

Quote:

Originally Posted by Claymore

sounds like your hitting boost cut, have you got an mbc on it?

That was what I thought. Yes I do have an MBC. However the boost is nicely under 1 bar so I'm a tad confused!

Kind Regards

Alec

caseyT5 · Apr 21st, 2011, 00:19

defo sounds like boost cut, i've been told many of times mbc's cause spikes which would cause the car to hit boost cut

allllec · Apr 21st, 2011, 00:28

Quote:

Originally Posted by caseyT5

defo sounds like boost cut, i've been told many of times mbc's cause spikes which would cause the car to hit boost cut

Again that was my gut reaction but the boost is not spiking when it happens?

Although only way to be sure is take the MBC out I suppose! Perhaps a job for the lovely weather and the long weekend!

thealchemyst · Apr 21st, 2011, 00:37

something that gives an almost exactly the same effect is the crank position sensor being faulty or having a broken/cracked wire, for some reason it shows up more under hard acceleration?

Claymore · Apr 21st, 2011, 07:43

the mbc can cause the afr to go lean at high boost, causing the ecu to cut ignition.

jonnyv · Apr 21st, 2011, 08:56

Hi,
The other thing it might be, which a guy on T5D5 found, was a previous Chav who had the car had put a blanking plate where the recirc. valve should be! Tosser! Also had a massive cone filter!!!
Result was maassive acceleration, the needle going off the white on the turbo gauge and a huge jam on the brakes when boosting too high, like a second or two after flooring it! Much worse when weather was cold!
Great guy removed the blanking plate, fitted recirc. valve and got rid of the cone. Car is perfect and no 'off the gauge' antics! Not as fast in pickup but I won't kill the Turbo!

Just a thought,

Cheers,

Jon

Apr 20th, 2011, 19:29	#1
allllec New Member Last Online: Jul 21st, 2018 17:06 Join Date: Oct 2010 Location: Reading	Big jerk while accelerating Hi there, Just seeing if anyone has come across this. If I floor my T5 auto occasionally there will be a massive jerk at a random point in the revs. (Feels like I've jammed on the brakes for 1 second) Feels like a really violent spark/fuel cut however the car is not over-boosting and I have no lambda lights etc. Anyone had this before? Kind Regards Alec

Apr 20th, 2011, 19:45	#2
The Hooded Claw Owner Volvovehiclesclub Last Online: Apr 4th, 2014 12:18 Join Date: Dec 2008 Location: Choosing which Volvo to go out in Today !!! lex parsimoniae View Photos By: The Hooded Claw	My Mrs read your Thread Title & thought you were talkin about ME drivin too fast (AGAIN!!) LOL!!! __________________ 2000 C70 T5 Phase 1 240 Bhp in Saffron Orange ("SAPPHIRE") 2001 S80 2435cc Now with Andy Northface () 1994 960 CD 3.0 Estate ("The Purple Monster") VOC 25900 lex parsimoniae

Apr 21st, 2011, 00:19	#6
caseyT5 Swedish Auto Parts Last Online: Oct 25th, 2020 23:42 Join Date: Feb 2009 Location: portsmouth	defo sounds like boost cut, i've been told many of times mbc's cause spikes which would cause the car to hit boost cut __________________ Visit our website www.swedishautoparts.co.uk Or Call us on 02392179161

Apr 21st, 2011, 00:37	#8
thealchemyst Master Member Last Online: Aug 22nd, 2018 20:57 Join Date: Apr 2009 Location: Coalville/Leicestershire	something that gives an almost exactly the same effect is the crank position sensor being faulty or having a broken/cracked wire, for some reason it shows up more under hard acceleration? __________________ 1995 850 t5 glt estate purple,FK-40mm,stainless exhaust polybushed,wilwood4pot+s60r discs,mbc,019 battery,18" c30 alloys,michelin pilots,silicone hoses,braided brake lines,HID's,ipd track swaybars 25+mpg :0) @Prescott Hillclimb

Apr 20th, 2011, 20:24	#3
Claymore VOC Member Last Online: Oct 27th, 2021 21:25 Join Date: May 2009 Location: Shrewsbury	sounds like your hitting boost cut, have you got an mbc on it?

Apr 21st, 2011, 07:43	#9
Claymore VOC Member Last Online: Oct 27th, 2021 21:25 Join Date: May 2009 Location: Shrewsbury	the mbc can cause the afr to go lean at high boost, causing the ecu to cut ignition.

Apr 21st, 2011, 08:56	#10
jonnyv Master Member Last Online: Feb 8th, 2015 12:06 Join Date: Jan 2011 Location: Cardiff	Hi, The other thing it might be, which a guy on T5D5 found, was a previous Chav who had the car had put a blanking plate where the recirc. valve should be! Tosser! Also had a massive cone filter!!! Result was maassive acceleration, the needle going off the white on the turbo gauge and a huge jam on the brakes when boosting too high, like a second or two after flooring it! Much worse when weather was cold! Great guy removed the blanking plate, fitted recirc. valve and got rid of the cone. Car is perfect and no 'off the gauge' antics! Not as fast in pickup but I won't kill the Turbo! Just a thought, Cheers, Jon

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