Hey All,

I have an 05 R53 S Hatch Back. Love the car and sooo much fun. I've done pretty well keeping it stock and have resisted the temptations to mod the crap out of it. Being a 6 speed automatic helps. Until I can get my hands on a manual 6 speed this is just fine.

I notices the other day that during a mild acceleration, I can feel multiple, slight hesitations. It only does it at lower RPM's but it's annoying. It doesn't really jerk or lurch, it's just not a smooth acceleration. No problem at high RPM's and I'm not getting a code, yet, but wanted some input before I started digging.

My suspects are: The fuel pressure reg on the fuel rail, the fuel pump, or MAF sensor. The plugs are new and clean, and I haven't found any vacuum leeks. I figure if it was injectors, it would generally run sluggish or cause a miss fire and throw a code.

Thank all,,

 

Not saying this is your cause, but most cars will run feedback control below a certain rpm, using the O2 sensor to trim fuel and ignition. Maybe your O2 sensor is getting fouled or old? Possibly the MAF needs cleaning too. Maybe try one of those catalytic converter cleaners or Seafoam through the tank?

 

ummmm -these cars don't have a MAF.
But yeah, try taking a look at fuel trims under the those conditions.

My personal opinion is that what you're experiencing might be completely normal. I bought my '03 R53 brand new and since day one it has been inconsistently lethargic at low RPMs. I suspect the DME firmware isn't the best.

 

I'm in total agreement with your vacuum suspicion, on the fuel pressure regulator..

On my car, the most frequently recurring problem I had was the damn vacuum line between the supercharger horn and the fuel pressure regulator vacuum control.
It originally kept popping off the fuel pressure regulator on me, and I'd notice exactly your symptoms - plus a hit on my fuel economy.

I eventually bought a new hose to replace it, and I'd also installed a boost gauge on my car so I had to tap vacuum for that, which I did with a tee at the other end - and then I had an issue with that joint.
So eventually I installed a mini vacuum manifold in a more accessible place and routed some vacuum lines to it - one to the supercharger horn, one to the fuel pressure regulator, one to the boost gauge sender.
What a pain.

I've also had MAF sensor issues (I think there's a T and a P, believe it was the T in my case) - which definitely came with CEL on the dash.
The vacuum to the fuel pressure regulator doesn't.

Also, it could actually BE the fuel pressure regulator - I'm tempted to replace mine just to be sure.

 

Seafoam is a magical elixir for cars.... I'll do that. I usually dump a bottle of Lucas in the tank a few times a year, but it's bean a while... Maybe my car's having withdrawals. LOL.. Thanks again for the tip. I'll update when I have something to update..

 

Thanks MrBean.. I hadn't thought of the software being possibly at fault. How do you check the version and update if necessary?

 

Thanks for the response.

Yea, my fuel economy is not so good right now either. I have had that line on the supercharger horn pop off... grr..

In that I'm not getting a code, I figure the MAF is functional.

I've bean contemplating installing a boost gauge. this may be a good time to tackle that one.

When I rebuilt the engine, everything but rear seals and rings, I didn't replace the regulator cause I was watching expense and figured I could do it later if needed. Let me know if you replace yours and it makes a difference.

 

Turn off your DSC and see if that makes a difference.

 

Will do...

 

It ended up being the Camshaft Position Sensor.
Replaced it and it starts immediately and runs great.

Thanks for all the input!!