TomWeight Posted October 4, 2016 Share Posted October 4, 2016 Took the car out on a short run earlier to the shops but on the return journey under acceleration, the car jerked and applied what felt like engine braking before returning to normal. First time it's happened and had no errors or lights come up on the dashboard but a bit concerning in case it's something sinister! Car has only just had a compression test in the last month which all came back fine so I'm not sure it's that. Car was also fully up to heat but it wasn't that long after ignition that I had to accelerate as the car park heads straight out on to a national limit bypass. Any ideas? Quote Link to comment Share on other sites More sharing options...
ibby Posted October 4, 2016 Share Posted October 4, 2016 Check battery terminals Quote Link to comment Share on other sites More sharing options...
Scooter Posted October 4, 2016 Share Posted October 4, 2016 How hard was the acceleration and how violent was the jerk? Also is the car stock Quote Link to comment Share on other sites More sharing options...
clay Posted October 4, 2016 Share Posted October 4, 2016 Sounds like you had feulcut. Quote Link to comment Share on other sites More sharing options...
TomWeight Posted October 4, 2016 Author Share Posted October 4, 2016 I was pushing the car to get up to speed but wasn't full throttle, say 75% Wasn't a violet jerk, felt almost like downshifting too harshly with just about a seconds worth of engine braking and no power then returned to normal. Worth saying the engine didn't change gear throughout. Car is stock apart from a decat and wastegate. The car is due a refill soon as its on about a quarter tank but it didn't feel like a fuel issue. :/ Quote Link to comment Share on other sites More sharing options...
clay Posted October 4, 2016 Share Posted October 4, 2016 No feulcut is when your car cuts the feul suply if you overboost. Quote Link to comment Share on other sites More sharing options...
Scooter Posted October 4, 2016 Share Posted October 4, 2016 As Clay says, it could be fuel cut.....do you have a boost gauge? Quote Link to comment Share on other sites More sharing options...
Wez Posted October 4, 2016 Share Posted October 4, 2016 Car is stock apart from a decat and wastegate. What wastegate is it running, do you have an FCD, what boost do you have it setup for? Quote Link to comment Share on other sites More sharing options...
TomWeight Posted October 4, 2016 Author Share Posted October 4, 2016 Ah right possibly then. Sorry for being full blown noob but anything to be concerned about? I kept an eye on pressures and temperatures the rest of the journey but didn't get anything out of the ordinary. Quote Link to comment Share on other sites More sharing options...
Jellybean Posted October 4, 2016 Share Posted October 4, 2016 Sounds like a misfire , might be worth highlighting the grade spark plugs are in there ? Model Number i.e NGK BEIX7 or IK22 Denso Quote Link to comment Share on other sites More sharing options...
Nic Posted October 4, 2016 Share Posted October 4, 2016 (edited) I was pushing the car to get up to speed but wasn't full throttle, say 75% Wasn't a violet jerk, felt almost like downshifting too harshly with just about a seconds worth of engine braking and no power then returned to normal. Worth saying the engine didn't change gear throughout. Car is stock apart from a decat and wastegate. Losing all power for a second sounds like it overboosted and hit fuel cut. The stock ECU will cut fueling if it sees above 1bar boost pressure, the removal of one of the cats could cause this raise in boost pressure. A boost gauge that shows peak boost would confirm this. If it is fuel cut you can either fit a Fuel Cut Defender (FCD) to raise the fuel cut limit or fit a restrictor ring in the exhaust to lower the peak boost below 1bar. Click on the highlighted words and -> BPU for a fuller explanation It could also be a misfire but this is usually a sustained hesitation/stuttering rather than a short, sudden loss of power. Edited October 4, 2016 by Nic (see edit history) Quote Link to comment Share on other sites More sharing options...
Scooter Posted October 4, 2016 Share Posted October 4, 2016 Also just to be clear if it is fuel cut, then this is the stock defence against excessive boost, excessive boost can quickly destroy the turbo's/engine. Nick has explained your options I just wanted to clarify the potential for issues if you don't make sure all the BPU parts are added as necessary before removing this safety barrier! Quote Link to comment Share on other sites More sharing options...
Littler Posted October 4, 2016 Share Posted October 4, 2016 It does sound like fuel cut but it does make the main MIL light and engine light come on, it also sounds like a possible start of a misfire. To go from a completely other angle with you coming out of a car park could it be that your tyres weren't gripping and the stock TC kicked in (but again dash lights would come up)? You mention a wastegate as a mod, on stock twins this is unusual? Quote Link to comment Share on other sites More sharing options...
TomWeight Posted October 5, 2016 Author Share Posted October 5, 2016 Thanks everyone for the help! It does have a restrictor ring which went on when the pipes were installed by whifbitz. After a couple more drives it has shown no more evidence of any problems, even on full throttle, but I did notice the boost getting fairly high so I'm going to take it easy this week and get it in the workshop at the weekend and have a proper look. Much appreciated! Quote Link to comment Share on other sites More sharing options...
Sandesupra Posted October 5, 2016 Share Posted October 5, 2016 could missfire like Jellybean wrote or a issue with youre seq setup.. sticky vsv, a leak or some sort.. if you had a boost cut you wouldent be in doubt about what it is! its a violent loss in power and feels like hitting a wall! ;-) Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 5, 2016 Share Posted October 5, 2016 I have my fuel cut defenders on the shelf if you need one. Changed yet another faulty HKS one the other day. Good luck with it. Quote Link to comment Share on other sites More sharing options...
Dnk Posted October 5, 2016 Share Posted October 5, 2016 When the traction control cut in on my UK car it felt like what you describe but you should see the trac light flash up on the dash when its doing it. When i suffered fuel cut it was as described earlier and a violent cut in power and the red warning triangle comes on Quote Link to comment Share on other sites More sharing options...
Nic Posted October 5, 2016 Share Posted October 5, 2016 Thanks everyone for the help! It does have a restrictor ring which went on when the pipes were installed by whifbitz. After a couple more drives it has shown no more evidence of any problems, even on full throttle, but I did notice the boost getting fairly high so I'm going to take it easy this week and get it in the workshop at the weekend and have a proper look. Much appreciated! Was it cold out when it happened? As the weather gets colder the boost will rise a point or two. Quote Link to comment Share on other sites More sharing options...
Wez Posted October 5, 2016 Share Posted October 5, 2016 Was it cold out when it happened? As the weather gets colder the boost will rise a point or two. the temp has dropped a little recently. Quote Link to comment Share on other sites More sharing options...
supra_jms Posted October 28, 2016 Share Posted October 28, 2016 Hi Tom, only just seen this! The car under my ownership never had a fuel cut problem but did similar as you described and that happens when the oem tc kicks in (snow mode). Your car has a restrictor plate and runs at 0.8 bar which is well within limits of turbos (1.2) i believe. Without obviously being with you it sounds exactly like a break in traction and the oem tc coming in. Hope you are still enjoying the car Quote Link to comment Share on other sites More sharing options...
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