HELP! erratic / uneven / laggy acceleration

[vypez]

i can be driving spiritedly to work when suddenly my next pick up at the traffic light is like a flat spot, and the rpm doesn't climb even though i am flooring the accelerator.

suddenly the rpm surges to 6k rpm and and the car plunges forward.

the car will be damn sluggish thoughout and even the gear charges are jerky.

i suspect its the fuel pump or fuel filter, or whatever, as i've just changed both oxygen sensors and knock sensor.

any other diagnostics?

 

[Red_Bean_Bun]

Re: HELP! erratic / uneven / laggy acceleration

Gearbox issues ......

 

[vypez]

Re: HELP! erratic / uneven / laggy acceleration

Gearbox issues ......

I thought so too, but if gas is full tank, runs smooth like a baby.

 

[Meek]

Re: HELP! erratic / uneven / laggy acceleration

Gearbox issues ......

Like gears not engaging?

 

[vypez]

Re: HELP! erratic / uneven / laggy acceleration

Like gears not engaging?

they engage, just like driving with cotton wool in the system and as if no petrol feeding in, until i floor the accelertor, then the car revs to 6k and speeds up.

 

[Ah yang]

Re: HELP! erratic / uneven / laggy acceleration

they engage, just like driving with cotton wool in the system and as if no petrol feeding in, until i floor the accelertor, then the car revs to 6k and speeds up.

Bro,check ur air flow also.

 

[M-Noobie]

Re: HELP! erratic / uneven / laggy acceleration

I thought so too, but if gas is full tank, runs smooth like a baby.

Interesting. What was the fuel level when this sluggish behavior started to show up? Is this behavior repeatable? ie full tank=smooth and when fuel runs low=sluggish. If so, you may want to bring your car in to check the fuel pump and fuel lines. I had a similar experience on my previous car but the behavior was the same regardless of the level of its gas tank. It was the fuel pump.

 

[vypez]

Re: HELP! erratic / uneven / laggy acceleration

Interesting. What was the fuel level when this sluggish behavior started to show up? Is this behavior repeatable? ie full tank=smooth and when fuel runs low=sluggish. If so, you may want to bring your car in to check the fuel pump and fuel lines. I had a similar experience on my previous car but the behavior was the same regardless of the level of its gas tank. It was the fuel pump.

honestly, i think its the fuel pump too.

feel like changing it to try it out.

 

[wt_know]

Re: HELP! erratic / uneven / laggy acceleration

no point try this try that
bring it to workshop for diagnostic and checking

can be due to many causes like maf sensor, throttle, fuel pump, valvetronic motor/sensor, etc

honestly, i think its the fuel pump too.

feel like changing it to try it out.

 

[pizzaboi]

Re: HELP! erratic / uneven / laggy acceleration

check with a reputable workshop first ?

no pt changing first if its not the root cause

 

[Baby1M]

Re: HELP! erratic / uneven / laggy acceleration

i can be driving spiritedly to work when suddenly my next pick up at the traffic light is like a flat spot, and the rpm doesn't climb even though i am flooring the accelerator.

suddenly the rpm surges to 6k rpm and and the car plunges forward.

the car will be damn sluggish thoughout and even the gear charges are jerky....

I thought so too, but if gas is full tank, runs smooth like a baby.

they engage, just like driving with cotton wool in the system and as if no petrol feeding in, until i floor the accelertor, then the car revs to 6k and speeds up.

All the 3 post above combined... does appear to be either the High Pressure Fuel Pump or the Low Pressure Fuel Sensor, it could be both too. More importantly, I can be VERY wrong

Ultimately, it is still best to go workshop for diagnostic and checking.

 

[LongIslandTea]

Re: HELP! erratic / uneven / laggy acceleration

Could it be solenoid or dirty ATF issues?

 

[Slayermarc]

Re: HELP! erratic / uneven / laggy acceleration

I also experienced the wooly feeling recently for the last 2 tanks. I even had jerky intermittent surges when I try to step harder on the accelerator.

This tank I tried a bottle of STP Fuel System which I got from NTUC. The car now runs normally and everything seems fine. I'm thinking there could have been a choke somewhere along the fuel system, maybe the injectors.

Crossing my fingers and hoping this problem doesn't come back!

 

[vypez]

Re: HELP! erratic / uneven / laggy acceleration

I also experienced the wooly feeling recently for the last 2 tanks. I even had jerky intermittent surges when I try to step harder on the accelerator.

This tank I tried a bottle of STP Fuel System which I got from NTUC. The car now runs normally and everything seems fine. I'm thinking there could have been a choke somewhere along the fuel system, maybe the injectors.

Crossing my fingers and hoping this problem doesn't come back!

yes sir!

thats the feeling i've!

 

[vypez]

Re: HELP! erratic / uneven / laggy acceleration

All the 3 post above combined... does appear to be either the High Pressure Fuel Pump or the Low Pressure Fuel Sensor, it could be both too. More importantly, I can be VERY wrong

Ultimately, it is still best to go workshop for diagnostic and checking.

after much pain, and trouble, ive found the source / issue.

mechanic recommends running on 98 entirely. its apparently some octane issue.

oh well. done!

 

[wt_know]

Re: HELP! erratic / uneven / laggy acceleration

after much pain, and trouble, ive found the source / issue.

mechanic recommends running on 98 entirely. its apparently some octane issue.

oh well. done!

better than car died on expressway because no fuel liao


**run away

 

[Baby1M]

Re: HELP! erratic / uneven / laggy acceleration

after much pain, and trouble, ive found the source / issue.

mechanic recommends running on 98 entirely. its apparently some octane issue.

oh well. done!

I was informed too, that interchanging between RON95 & 98 will bring about the issue, the issue is the Fuel Sensor starts to go haywire. Frequent change of brand (same RON) can also affect this sensor, so I was told by BMW SE/SA.

 

[davidtch]

Re: HELP! erratic / uneven / laggy acceleration

after much pain, and trouble, ive found the source / issue.

mechanic recommends running on 98 entirely. its apparently some octane issue.

oh well. done!

That's why i have been advocating running on Ron 98 at all time (unless in MY). All my cars runs on Ron 98 only including my current JDM.

 

[Red_Bean_Bun]

Re: HELP! erratic / uneven / laggy acceleration

Odd. It means your car has a tendency to knock ?

after much pain, and trouble, ive found the source / issue.

mechanic recommends running on 98 entirely. its apparently some octane issue.

oh well. done!

 

[Red_Bean_Bun]

Re: HELP! erratic / uneven / laggy acceleration

Hard to believe. I think you should pull the error codes out and have a look.

I was informed too, that interchanging between RON95 & 98 will bring about the issue, the issue is the Fuel Sensor starts to go haywire. Frequent change of brand (same RON) can also affect this sensor, so I was told by BMW SE/SA.