Porsche 911UK Forum

Welcome to the @Porsche911UK website. Register a free account today to become a member! Sign up is quick and easy, then you can view, participate in topics and posts across the site that covers all things Porsche.

Already registered and looking to recovery your account, select 'login in' and then the 'forget your password' option.

What could be the cause of hesitation when accelerating?

I`ve just had a watch of some of the videos of the Pico Scope, that looks like a really usefull tool and will come in handy with work too, thanks Ghianightmare, a 2 channel version is available at RS components for £100, no brainer really :thumb:

Chris, having watched those videos, particularly one on how to read the MAF, it does look like a likely cause for your issue, a mass influx of air on WOT that the ECU can`t see if the MAF is faulty :?

I`m having a slight issue on the 996.1, idling was all over the place the other night after not using the car for a month and fitting a new battery due to a dead cell, car was jumping from 600 rpm to 1200 almost as though I was blipping the throttle :sad:

I shall be watching this thread with interest :thumb:
 
I hate not using them as much as I did, they love to be used, I've had so many niggly issues with the 996 in 2018.

New Years Resolution, drive it more often.

That Pico Scope sounded like a good bit of kit but I forgot to check it out after I'd read about it in that thread.
 
kurlykris said:
I`m having a slight issue on the 996.1, idling was all over the place the other night after not using the car for a month and fitting a new battery due to a dead cell, car was jumping from 600 rpm to 1200 almost as though I was blipping the throttle :sad:
:

Whip your idle valve off the throttle body, it should snap open either way with a 9v battery. I dismantled mine to clean up, it was stuck after 3months of no use. Just push the little roll pin out, care not to crack the plastic like I did.

Also usual check for vacuum leaks.
 
I manged to get some garage time today and it seemed the easiest thing to do it just swap the MAF over as it was in my hand. I was going to do each job I intended to do and test drive it between so I knew exactly what I had done to cure this.

I fitted the MAF and it fired up fine, I let it warm up a little and took it for a spin, it seems the MAF was the problem. It didn't hesitate at all, I did feel it wasn't 100% as it should be but this may be down to the coil packs being quite old as I recently had one fail. I'll run it from stone cold to make sure 100% but I'm sure this has been solved with a new MAF :thumb:
 
Whist this is good news i want you to drive 20 miles at least then give me some readings from your durametric .. obvioulsy sort the tank issure first on your other post .

What im after is maf readings and fuel adaption figures plus any fault codes .

You may have to clear the codes then do a 20 mile r/t and recheck for codes though.

When you clear a fault code it also resets the adaptions .. this is for basic wear and tear so the car needs to relearn these before it will run correctly , you will have the odd air leak or rich mixture that the car will adapt to so you always clear the codes then give it a good run before rechecking for faults .

lambda faults take 5 - 10 days to re occur ... you just have to wait before checking for these faults ... see my boxster thread !!
 
I was home really early from work today, so decided to have a play with the 996.1. I popped the MAF out and it looked brand new, clean as a whistle and the green o-ring looked like brand new, I had a poke around the Idle Control Valve and wiggled the plug a bit, but I couldn`t get my torx driver on the back screw as there was a plastic pipe in the way and I didn`t want to have to start stripping half the engine bay down on a school night.
I warmed the car up on the drive, turned the engine off and then plugged the iCarsoft 960 in, started the engine again. Revving the engine from the throttle cable :D I heard a distinct click from the ICV. When I had the problem the other night, I noticed that if I turned the Aircon on and off, there was no change in RPM at idle, which now there is :grin: all seems to be back to normal, maybe having sat out in the cold for a month she was just having a strop and just jealous of me using the Boxster over Christmas :lol:

Unplugging the MAF with the engine running, the RPM dropped to almost stalling then picked up to a lumpy idle

Anyhoo, I took a photo of the Airflow at Idle and up to temp.
4.99 g/s equates to 17.964 Kg/h at idle :thumbs:

yi8chqh.jpg
 
Maf is spot on were it should be .

If you have the early IACV .. black box on the side of the throttle houseing then a remove and a good clean out is always a good idear .. like the old Bosch ones they can and do stick.

Is the last reading on your gauge the post cat lambda sensor for bank 1 ?

Its only that the reading is spot on what a dead sensor would read .

You tend to do a quick stamp on the acc and it should rise and then fall to prove its ok .

Something people also forget these days .. clean out the throttle butterfly .. i did a Boxster last week .. i ended up removing it as it was that bad .
 
Yes it is the Lambda demort, I`m sure that is the one that was changed last year for the MOT, I`ll stick the code reader back on tomorrow night and look for some sign of life and compare to bank 2 :thumb:
I`ll most probably pop the throttle body off at the weekend and give it all a good clean, I did open the butterfly and it looked a bit grubby inside :grin:
 
I expect it will be fine and at the end of the day its there to check the cat , it has no bearing on the performance of the car.

Its kinda strange that an eml is triggerd far more by save the planet stuff than it is for actuall engine running faults !

I scoped a brand new cat with new sensors today .. it hardly moves from Lambda .. 0.5 v ..

Basically stamp on the throttle to the floor and back up ( engine running ! ).. there will be some switching to rich (higher voltage ) then lean ( lower voltage ) and that proves its working fine .

Front sensors .. so pre cat .. graph both and your looking for a constant rich / lean switch ( 0.2 - 0.8 v ).. they should almost mirror each other .. if one is lagging behind then your getting into ageing faults .. this is where one lambda sensor switches slower than the other and so generates a fault code .

You dont actually have any codes so nothing is out of specs .. but its always interesting to have a look and get your head around these things .. hence i waffle on about it :D

Fyi .. 997 has different sensors so the above is not true ... these are called wide band sensors .
 
deMort said:
I scoped a brand new cat with new sensors today .. it hardly moves from Lambda .. 0.5 ..

...dirty... :hand: you'll have the RSPCA on your back now :D

But nice to see the scope got some use in this thread :thumb:
 
deMort said:
Its kinda strange that an eml is triggerd far more by save the planet stuff than it is for actuall engine running faults !

I heard the origins of these lights is in emissions regulation. In the states it was a legal requirement that a light alerted you to emissions fault, and the car would not pass inspection The regulators didn't care about engine faults... and mfrs didn't want to concern drivers with minor faults that could be picked up at service.
 
Ghianightmare said:
deMort said:
I scoped a brand new cat with new sensors today .. it hardly moves from Lambda .. 0.5 ..

...dirty... :hand: you'll have the RSPCA on your back now :D

But nice to see the scope got some use in this thread :thumb:


:floor: .. ill try to leave the cats alone in future :D

Wasz .. you are correct .. CARB was one of the first emmissions based regulations in the world .. it pre dates OBD .. a police officer could pull your car over .. plug in a tool and check the emissions .. if it failed then it was a tow truck .

Strange that USA has now moved away from the kyoto agreement but hey hoe ... thats politics .

To have a warning system thats based more on the save the planet stuff rather than enigne faults is strange , i dont understand it but thats how it is .

CARB = California Air Regulations Board .
 
I decided to clean my throttle body while I am still waiting for other parts but it was as clean as a whistle.

46623950652_c6b4b8e321_z.jpg


Took it out for a 25 miles drive today and it still seems fine even driving straight from cold. I'll try to get some readings tomorrow and post up what it is actually doing.
 

New Threads

Forum statistics

Threads
124,356
Messages
1,439,463
Members
48,715
Latest member
911tt1
Back
Top