As per title..

Since January the car has had:

Full gearbox rebuild, plastic coolant hoses replaced, supercharger vacuum pipe replaced, smaller top supercharger pulley, supercharger coupler, supercharger oil, diff oil replaced., all spark plugs replaced (twice), all fuel injectors replaced, rear-wheel bearings replaced.

The latest work was less only a couple of weeks ago which was all of the fuel injectors (one of them cracked, so I had them all replaced). It has been driving fine for the past couple of weeks and then today driving on the motorway I thought I heard the revs jump ever so slightly and remain higher with absolutely no change in car speed or throttle position. This was so subtle I thought I might have just imagined it.

After I got off the motorway, I noticed under gentle acceleration at low revs (around 3rd gear) the car was kangarooing/surging. The gentler the acceleration, the worse the problem.

No EML, I even tried to get it to throw an EML by intentionally causing it to kangaroo, but nothing. Hard acceleration shows no issues at all, everything seems perfectly fine. I've ordered some MAF cleaner, that should arrive tomorrow, but I've looked at the MAF's a few months ago and they looked immaculate.

I'm supposed to be driving my brother in law to his stag on Saturday

Does anyone have any ideas?

--- Update:
Just taken it out again and it's running perfectly fine now. So appears to only be an issue when hot. I have to work so I will take it out in my lunch break and warm it up to see if I can reproduce to confirm.
It *could* also be an 'only when wet' issue, as it hasn't been driven in the wet since coming back from the garage.

 

Which of P1000 or P1111 do you have?

If P1000, which OBD monitor(s) is/are unset?

 

I'm not getting any CEL, I can't check if there are any none-cel codes until the Mrs' gets home from work, as my scanner is in the other car.

I will scan for codes when she gets back though.

> If P1000, which OBD monitor(s) is/are unset?

Not sure what this means sorry chap?

 

Update: P010B (Maf on bank B)

I'm not sure if Bank B is on the left or right side of the car when facing it looking into the engine bay. But I've swapped the MAF's around, I'll go for a drive later and see if the code swaps sides...

 

Okay, took the car for a drive down the motorway for 24 miles. Ran absolutely fine, until the end of the drive when I got off the motorway, then started jerking/jumping/kangarooing again. A bit of testing reveals this is at a very specific throttle position in a very specific rev-range.

Between 1250-1900rpm, at light throttle (normal around town acceleration from 30-40). Heavier throttle (say half throttle fast accel) or higher RPM (2k) the issue doesn't show itself. In fact as soon as you get over 2krpm the jerking suddenly stops.

It also happens in any gear as long as the above remain true (I tested this by going into manual and accel gently from 50-80ish in 6th).

P010B came back (despite swapping the MAF sensors around) and I have a new code: p061a

Update: Clearing the codes and going straight back out for a drive appears to fully resolve the issue. This makes me wonder if the P010B is causing the car to ignore the MAF sensor values, and fall back to default 'safety' values. And it's the default safety values combined with my mods that are causing the kangarooing (supercharger pulley, some exhaust mods + remap).

 

https://www.obdautodoctor.com/scanto...tors-explained

If only the web had a way to search it.

 

My bad, sorry. I didn't have a way of checking that regardless.

I *Think* I've resolved the issue by giving the mafs a bath in iso and replacing the air filters. The problem hasn't come back thus far. Didn't want to report back until I'd done some miles to be sure as it only showed itself after 24 motorway miles previously.

Looks like it was seeing a mismatch in air between the mafs and falling back to 'safety fueling' (or whatever the correct term is) which was causing the issue.