The car stumbles, or hesitates, or chokes when I blip the throtle from idle. If I gradually depress the throtle the revs go up smooth. It is only when I blip the throtle. Problem is getting the revs up from idle if I depress the throtle suddenly.

As a result, I always have to put it in 1st gear when coasting from a stop sign (no I don't always come to a full stop). Used to be able to put it in second and go.

Car starts fine when cold.
Goes through the gears fine, nice and crisp
Idle is steady
No hesitation accelerating on the highway (when the revs are up)

It is my wife's car, so I don't drive it often. We just installed a catback and I was blipping the throtle to hear the new exhaust. That's when I felt the symptoms.

The problem I am told has been going on for a while.

Any ideas or comments to point me in the right direction is appreciated.

I was going to get a canned flash, but would rather wait until I get this sorted out.

Although, the flash may correct the problem if it is an ECU issue.

What do you think?

Thanks

just try resetting the ECU its easy and will probably fix your problem.

and are you trying to take off from a stop in second? thats not good at all.

#Still rolling.

I've done the reset. But will try again.

The research I've done seems to point to:
1. Vacuum leak
2. Timing, air/fuel
3. Plugs/Wire - Less than 10k

What would you do to troubleshoot? I have ordered a PCV valve from the dealer.

Probably a weak spring in the bypass valve. Does the car seem to jerk slightly when you depress or release the throttle abruptly from a low-throttle angle?

Check fuel distribution/pressure: filter & pump.

I'd go for vac leak, TPS and fuel pressure/filter. Plugs etc non starter as you have no other symptoms.

I think minisanity has a good point.Check fuel pressure. Thats the same thing my truck did when the fuel filter was dirty and it took me a yr to believe someone and try it. We always start with the hard stuff.

Went thru everything to cure mine of it. From plugs, wires, gas, injector cleaning, vacuum leak check, BPV, harmonic damper change. Checked rail pressure, way low. Replaced rail pressure regulator, still no go. Filter, no go. Finally, checked pump, had a torn in-tank fuel hose from pump to filter....Did it step by step in chronological order above. Wished I reversed it. The pump & filter had never been previously touched since new. One of those unexplainable mysteries in life.

Update: Had a GIAC flash done for $400, which has fixed the issue.

Apparently, the stock ECU was unable to compensate for the combination of engine upgrades I have on the car.

15% pulley, CAI and Catback, MSD wires/coil and colder range plugs.

I would describe the flash as having smoothed out the way the car runs, no monster power kick in the pants experience. Realistically you can only make so much HP/TQ safely from a 1.6 4 cylinder engine. I am satisfied.

I'll be focusing on handling upgrades next. Already have front stress bar, cabrio braces, under brace, 22mm sway bar. New tires, lighter wheels and shocks next.

Thank you for all your responses.

I have the same issue but I have no upgrades on my vehicle. Got a fuel filter and waiting on the fuel pump to come before I install everything.

Hi All

Good day. I have the same problem for my R56 LCI model as well. Replaced new fuel pump, fuel filter and HFPF. Still facing the above issue. Only upgrade to the car is Wagner Tuning intercooler. Thanks.

Hello! Have the same issue. have you sorted it out?