Acceleration Jerking

[Atters_del]

So I took my CC GSR for a 1000km drive and at about the 700km mark while slowing to drive through a town everything was fine until I hit the 100km/hr sign and started to accelerate the car didnt want to go, it jerking and coughed abit then struggled to 100km/hr. It was fine until I hit boost at about 3000rpm then it didnt like it at all. I thought I might have had some dodgy fuel from a 1 horse town ( Shell V Power which I always run ), I was at about 1/4 tank so at the next town I filled up with BP Ultimate and all seemed well for about 30mins until I went to overtake a truck then the coughing started again. Car runs perfect in 5th at 100km/hr at 3300rpm, but when you want to accelerate it really feels like its struggling. Any Ideas boffins?? .. btw I was running the stock GSR ecu, then changed it after I filled up at BP with a MEEk tuned ecu that I run always, and ran fine..seemed very inconsistent ..one minute feel fine, then slow down to 60 for a town then ran like crap till 100km/hr then smooth?? Oil Changed 3000km ago, Spark Plugs done 3000km ago, ODO 193000km

 

[clone]

only struggles at 100 when you put your foot down or at all speeds?

 

[Gianni]

How was fuel consumption? Is your MAF plugged in or loose?
Otherwise I would be thinking some kid of boost leak or something tune related (which could be due to extra or not enough air from a leak) that would explain jerking.
Otherwise if its just constantly extreamly sluggish I'd look at your CAS and timing

 

[Atters_del]

Fuel consumption was normal, (approx 400km from tank). It was running perfect until I slowed for a town to stop at the lights. Went to take off again and bump bump jerk bump ugh..what the? .. backed off under boost and it was ok, put foot down- nup doesnt like it. I stopped and checked all the points, hoses etc, Vac was at 20. Runs fine not on boost..then seemed to clear itself for about 150km then came back when I slowed for another town.

 

[Atters_del]

Clone- struggles at all speeds. BUT it happened all of a sudden..then cleared then came back 150km later

 

[Gianni]

I had a similar thing, it would drive fine down low. Boost but after 5k would shudder and shake heaps.
Once I got the car tuned it disapeared. I say air fuel ratios.
From memory it was fuel cut, ecu registers too much air so cuts fuel to prevent anything bad happening. I'm not sure why yours would do it if you haven't changed anything. Perhaps the chip has formed an issue but that's beyond my knowledge.

 

[Gianni]

But if yours is doing it at all speeds I'd say fuel pump or maybe faulty MAF ifit sometimes works fine
Could be timing but it would be like that constantly, not randomly good bad other times

 

[Atters_del]

UPDATE - I removed and checked all spark plugs - GOOD
- Checked all leads - GOOD
- removed K&N filter (stock airbox) checked for debris etc - GOOD
- tightened all hoses and fittings (they were loose) now - GOOD
- The blow off valve plumb back came out when I pulled it, removed bracket, new bracket tightened - GOOD
- Start up - idle 850rpm VAC 20 .. OK TEST DRIVE ... smooth out drive way, turn left WOOOOSH .. ok FIXED.

Thanks for the help guys in helping me narrow down the problem. This forum is golden.

 

[clone]

lol make sure your intercooler piping is tight and that your hose on your fuel regulator is on solid if not chuck a zip tie on there

 

[EVO-00X]

IMO it could be a dodgey O2 sensor playing with your A/F ratios.
This could be the reason why you have issues when you're driving through the towns at low speed/ when your exhaust temps drop, then the engine reacts differently when you're pushing for higher rpm and creating hotter exhaust temps.

 

[CLuTZ]

Sounds like you had a boost leak