523iA 1997 Sluggish/Poor acceleration under 3500rpm

[JaxKiBez]

I've been facing this problem too long, car accelerates at varying pace, from idle to 3500rpm car is like 70bhp, it feels like there is some thing that holds car back.
And at 3500rpm car surge to full power almost all the way exept at 5000rpm there is slight surge again.
There is no difficulties at startup, no difference between cold and warm engine. Fuel usage is also around 10-11l/100km when my earlier 523iA went for 8.5-9.5 same driving.

No fault codes at all, VANOS works instatly when activated from INPA

INPA gave adaptations like this:
Fuel control integrator 1: 4
Adaptation value add 1: -51
Adaptation value multiply 1: 14

Fuel control integrator 2: 0
Adaptation value add 2: -23
Adaptation value multiply 2: 13

Changed parts:
- Cam-pos sensor OEM
- Sparkplugs NGK BR6EK
- Rubber between throttlebody and MAF-sensor
- Airfilter

Could anybody help me

[LuisGT]

I had an identical problem... turned out to be a clogged cat in my case, cheap ebay headers and the car feels beastly again...

[granlund]

And at 3500rpm car surge to full power almost all the way exept at 5000rpm there is slight surge again.

No fault codes at all, VANOS works instatly when activated from INPA
This is a classical symptom for worn out VANOS piston seals. Just because the solenoid works and can be activated by INPA doesn't mean that it can advance the cam.

If VANOS can be activated by INPA btw., what happens if you do that on idle? The engine should run rough and possibly even stall.

[JaxKiBez]

This is a classical symptom for worn out VANOS piston seals. Just because the solenoid works and can be activated by INPA doesn't mean that it can advance the cam.

If VANOS can be activated by INPA btw., what happens if you do that on idle? The engine should run rough and possibly even stall.

Yeah idle was race-car like when activated VANOS, now i did some livedata-session here are results:
VANOS-activated normally when driving from around 24-degrees to over 40-degrees instatly, not much delay

Adaptation values befores Cam-sensor change
Fuel control integrator 1: 4
Adaptation value add 1: -51 (Idle)
Adaptation value multiply 1: 14 (Partial load)

Fuel control integrator 2: 0
Adaptation value add 2: -23 (Idle)
Adaptation value multiply 2: 13 (Partial load)

Adaptation values after Cam-sensor change (~300km)
Fuel control integrator 1: 0
Adaptation value add 1: 0 (Idle)
Adaptation value multiply 1: 7 (Partial load)

Fuel control integrator 2: 0
Adaptation value add 2: 13 (Idle)
Adaptation value multiply 2: 8 (Partial load)

So, Livedata in cold start around +4 celsius gave this information

Idle:
- Engineload 127-135 mg/stroke
- Air use of the idle control valve 20.75kg/h
- total air use of air mass flow sensor 21.00kg/h

Engine Roughness
Cyl 1 - ~1000
Cyl 2 - 0
Cyl 3 - ~0-170
Cyl 4 - ~130-190
Cyl 5 - 0
Cyl 6 - ~50-150

I unfortunatly didn't get idle-value from warm engine, my laptop run out of battery before i got home. I try again tomorrow to get those values.

Then i noticed throttle pos-sensor giving 0.6V at no throttle and 3.47V at full throttle, is this normal values?

[ferguscan]

Hi Jax,

I have a '96 523iA with similar problems. I've been chasing them for years (!) now. My car also feels like a dud up to 3k RPM. After that it feels fine. I have the same fuel usage as you. Do you experience any of the following:

- engine sounds louder than it should
- car starts every time, but sometimes feels like its catching too early or too late

For my part, I have replaced the following:

- injectors
- spark plugs (old ones looked fine)
- coils
- CCV and hoses
- Vanos seals
- air filter
- fuel filter
- fuel pump
- fuel pressure regulator
- fuel tank purge valve
- intake manifold and throttle body gaskets

EDIT:

- cam and crank sensors too (both OEM)

And probably a bunch of other stuff I can't recall just now. None of it changed the issue. Like you, my Vanos responds instanly in INPA.

I get no codes. Do you get any? Our issue might be the same. If we put our heads together, we might be able to solve it.

Feel free to PM me.

Thanks,

Stuart

- - - Updated - - -


I had an identical problem... turned out to be a clogged cat in my case, cheap ebay headers and the car feels beastly again...

** Just to confirm: you had a clogged cat, and your car performed BETTER at higher RPM? I've heard that cars normally perform worse at high speed/RPM with a clogged cat. That's why I ruled it out as a possible cause.

Thanks,

Stuart

[JaxKiBez]

Nice to know that im not the only one.
I don't think my engine sound any louder than it should, but when driving windows down, exhaust sounds little raspy and i've been thinking if exhaust have something to do with this. But that can be tested in annual inspection, if exhaust emissions show something.
When looking list you've changed in car, we should look elsewhere. What could it be:
- Exhaust
- O2-sensors
- ICV
- MAF
- Something electronic?



Hi Jax,

I have a '96 523iA with similar problems. I've been chasing them for years (!) now. My car also feels like a dud up to 3k RPM. After that it feels fine. I have the same fuel usage as you. Do you experience any of the following:

- engine sounds louder than it should
- car starts every time, but sometimes feels like its catching too early or too late

For my part, I have replaced the following:

- injectors
- spark plugs (old ones looked fine)
- coils
- CCV and hoses
- Vanos seals
- air filter
- fuel filter
- fuel pump
- fuel pressure regulator
- fuel tank purge valve
- intake manifold and throttle body gaskets

EDIT:

- cam and crank sensors too (both OEM)

And probably a bunch of other stuff I can't recall just now. None of it changed the issue. Like you, my Vanos responds instanly in INPA.

I get no codes. Do you get any? Our issue might be the same. If we put our heads together, we might be able to solve it.

Feel free to PM me.

Thanks,

Stuart

- - - Updated - - -



** Just to confirm: you had a clogged cat, and your car performed BETTER at higher RPM? I've heard that cars normally perform worse at high speed/RPM with a clogged cat. That's why I ruled it out as a possible cause.

Thanks,

Stuart

[LuisGT]

My car was a dog below 3200 RPM, in 5th gear it could not maintain speed at all and I often had to drop a gear... above 3200 RPM it felt somewhat normal, but I had also replaced the vanos seals... Normally in manual mode it selects 2nd gear when coming to a stop, mine had a hard time pulling from a stop in that gear when it previously didn't. After replacing the catted exhaust manifold with Ebay headers my car pulls in 5th gear and it gained a few horses across the powerband as well... according to the butt dyno... and it pulls in 2nd gear like nobody's business.

[ferguscan]

Nice to know that im not the only one.
I don't think my engine sound any louder than it should, but when driving windows down, exhaust sounds little raspy and i've been thinking if exhaust have something to do with this. But that can be tested in annual inspection, if exhaust emissions show something.
When looking list you've changed in car, we should look elsewhere. What could it be:
- Exhaust
- O2-sensors
- ICV
- MAF
- Something electronic?

** I've not yet tested my exhaust. I've been thinking about doing a back-pressure test around the Cat.

My O2 sensors appear to be working normally, but who knows? My car takes the expensive type of sensor, so I'll probably replace those last. Feel free to try that at your end.

I've cleaned my ICV, but not replaced. My rev gauge doesn't move when I'm idling, but the idle is lumpy, so it's possible?

I've tried running the car with the MAF disconnected. It didn't run any better, and maybe slightly worse. To my mind, this ruled out the MAF. But feel free to correct me.

I suspect it could be something electronic... any ideas?

I'll do the exhaust back-pressure test sometime in the next fortnight and report back.

Thanks,

Stuart

[larrym3711]

Do something 'simple' for now. Remove and inspect each spark plug one at a time. I am guessing there are clues there to be evaluated one at a time. My guess is you still have an input leak or fuel condition(like a leaking injector) which will show up as unusual plug colors. I am ignoring possible rough idling due to (possible) internal compression deviations. The other possibilities, including O2 sensors, remain as possible culprits. ICV can cause idle problems, but usually manifest themselves as hard starting or other inconsistent behavior (due to worn internal parts or sticking).

larrym3711
2001 540iA Sport