Surging under full throttle

[python1]

Under full throttle accelleration I feel a surging as speed picks up. I have replaced the ing. coils, fuel injectors, spark plugs, and fuel filter. has anyone had the same problem? and what was the fix?

[python1]

Oops I forgot 1994 BMW 525i

[SRR2]

Surging? My wife has a PT Cruiser that when you accelerate at anything above 1/2 throttle has a torque curve that looks like Cheney's heartbeat when he thinks about Halliburton's next ten billion dollar no-bid contract. The car has done this since day one and I always chalked it up to the constricted suboptimal design of the intake and exhaust headers. I've never had a BMW do that, so I suppose the first question I'd ask you is whether the exhaust system has been modified. Otherwise, have you measured the fuel pressure and checked the condition of your MAF and O2 sensor?

[winfred]

i find it's usually a slow 02 sensor

[SRR2]

How would you diagnose a 'slow' O2 sensor? Are you saying that the voltage actually does vary according to the spec, but for some reason it's delayed in tracking the instantaneous variations in exhaust composition? Or do you just replace it because in your experience 99 times out of 100 this is the cause?

[python1]

As far as I know the O2 sensor has not been replaced in 156,000 miles, guess it might be dirty, any other suggestions would be welcome. What about fuel pressure regulator?

[winfred]

when the 02 sensor gets really old it's reaction time gets slow and doesn't feed the computer the info it needs at the right time, if it's got 150k on it id say replace it, even if it's not the problem it's way past due and you will probably gain a mpg or two even if it doesn't fix the surge, the sensors hardly ever outright fail in my experence, i can test their reaction time on the bench and tell exactly how good/bad the unit is, if you have access to a graphing multimeter i can tell you how to test it, it's hard to tell the reaction time with a regular digital multimeter

[Derek A.]

o2 sensor is cut out at WOT. To the best of my knowledge its a fixed ignition/fuel map. I would look at fuel pressure/volume and then take a look at any leaks in the induction system. Many times the airflow meter connector belows get cracks/holes.

[632 Regal]

agreed.


o2 sensor is cut out at WOT. To the best of my knowledge its a fixed ignition/fuel map. I would look at fuel pressure/volume and then take a look at any leaks in the induction system. Many times the airflow meter connector belows get cracks/holes.

[liquidtiger720]

My car use to surge on acceleration- I had a leak from the intake elbow to the icv? . I clamped up the hose, and it went away. :)

[python1]

Thanks guys I will give all your ideas a go. I will let you all know what the out come is and what corrected the surging.