Z3 power loss problem

[mini1380cc]

Hi Guys hope you can help with a problem i have. I recently picked up a Z3 1.9 as a spontaneous purchase and so far its not been a patch on my e39.

One thing that i'm looking to fix is a flat spot after 4000rpm. The car pulls as i'd expect until 4000rpm then it instantly drops in power then struggles to reach 5000 rpm, wont even attempt 6000rpm.

My first step is air/oil and plugs change but what else should i look at? Does the M43 engine have any common issues surrounding this symptom?

As it stands i'm shifting as if its a diesel but i'd like to make use of the intended powerband.

Any help appreciated.

Edited by mini1380cc on Monday 6th June 22:12

[trickywoo]

Your first steps sound good.

Could also be a sensor issue. MAF / O2? Might be worth running diagnostics.

[mini1380cc]

Just had the codes read by a Snap-On Solus and it came back with - 170 o2 Sensor Heater after CAT.

Is it a safe bet that the o2 sensor needs replaced?

Would a defecting CAT throw the same error?

[steve_bmw]

had the same problem with my girlfriends car the other week, no power above 4000rpm, using lots of fuel too, replaced the o2 sensor and all is well.
Go to your local mot centre and ask them to check your emmissions!

[mini1380cc]

Thats the thing. Its got a fresh MOT on it (emissions passed).

I bought the car from auction (hey cheap z3, what can go wrong eh! ) with a fresh MOT so i thought the emmisions would be fine. I have not had the emissions done yet but i dont really trust the fresh MOT at all now given that the car passed the test with front brake pads down to the metal backings, it was actually metal on metal.

o2 sensor has been order and brakes refreshed all round.

Thanks for the replies.

Ps i'm hoping the new sensor will bring up the MPG as i currently get better from my 523i.