Kangaroo jumping under full boost (Fault Code Update) ***Solved***

[OSR]

Hey All,

So I have a 1.8T AUM engine code running Revo Stage 2 software.

Recently when under full throttle in third gear I've had the car "kangaroo jump" as I've climbed the rev range. It's the best way I can describe it, kind of like a misfire but not, more like it's very temporarily losing all boost then getting it back. It may do this two or three times in almost rapid succession if I keep the throttle down but I've obviously been letting off in case I do any damage.

I've run my fault code reader and I'm code free (took me years to get rid of the pesky 17705 code  ). I'm ruling out misfire partly due to no codes, but also as it doesn't "feel" like a misfire (had my coil packs go a number of years back).

Fault code update:

16684 - Random/multiple cylinder misfire detected.
16688 - Cylinder 4 misfire detected.

In summary the following parts have been replaced over the last few years/20k miles;

All 4 coil packs circa 25k ago
New N75 valve circa 10k miles ago
N249 delete etc ages ago, but with all new vacuum hosing circa £10k miles ago
No boost leaks whatsoever
New 4bar FPR (Bosch) at the time of Stage 2 map circa 5k miles ago

I'm leaning towards the actuator, partly as it's original (100k+ on it) but also as I believe they tend to be the weak link once you get beyond boost levels seen in Stage 1 maps? My question is, does a dodgy actuator fit the symptoms described above?

The only other thing I can think of would be the fuel pump, but would this not throw a code as it would ultimately be linked to the injectors/AFR?

Any comments of suggestions appreciated. It doesn't affect the car on a daily basis but is niggling me as I'll need to sort it!

*** Problem now solved - it was indeed the coil pack on Cylinder #4. ***

Thanks,

OSR.

[Dalo Harkin]

If its the original actuator, I would change that anyway to rule it our, especially on a stage 2, I run the forge one with a yellow spring in it, what boost are you running? mines around 1.7bar and it holds perfectly

[OSR]

Hiya,

Yeah boost is around 1.7 and was holding fine just after I had the map done but guess it's taking its toll! I do need a new clutch as well as I caught it slipping when i was driving a lot at xmas - usually when you drop a gear to overtake etc.

Both parts on the list so guess I'll get them bought and wait for some nicer weather to fit 

Is fitting the actuator a big job? Had a read around at how to guides and it potentially means dropping the exhaust, turbo off etc?

Cheers.

[Dalo Harkin]

Yeah it can be, I managed to do mine while it was all on, I did have to drop the DP slightly.
I went for the G60 flywheel and VR6 clutch in prep for my stage 2, it struggled on the standard one with a stage 1 

[OSR]

Hmmmm as I suspected, oh well, nothing is ever easy

Well I'll likely do it at the same time as the clutch - I guess with the gearbox out the way access will be a bit easier.

I notice from you're sig you've deleted the carbon canister - not come across this before, worth doing or just to tidy things up a bit? Think mine's leaking fumes due to a split hose.

[Dalo Harkin]

Yeah mainly to tidy the bay up a bit, one of my next projects is to relocate the battery to the boot, and get some meth! just not got around to it yet

You running an FMIC?

[OSR]

Yep got the THS one. Fitted it a couple of years ago but to be honest still need to get the bumper off to trim a little bit more, just never found the time!

I sorted everything before I went for the Stage 2 map, other than clutch, and actuator 

[Dalo Harkin]

I'm surprised they even did it with the original actuator on 

[OSR]

Yeah, managed to hold up all right - came in bang on 230bhp/250lbs and 200bhp at the wheels which is apparently what a Revo Stage 2 should come out with I believe.

I know RTech Stage 2's with the same hardware (plus actuator) can get up to 260bhp but I had an RTech Stage 1 on there previously and the Revo guys up here said they couldn't get it to run right for the "before" run as it was over boosting like mad? To be fair RTech were spot on when I visited them a few years ago for my Stage 1, the main reason for going Revo was moving to North East Scotland so it was just too far a journey when there's a Revo dealer here in town but I've been impressed with the Revo map so far.

[OSR]

Update on this one, drove the car fairly hard last night to see if it was a consistent issue and this time it threw the following codes;

16684 - Random/multiple cylinder misfire detected.
16688 - Cylinder 4 misfire detected.

Basically I think under full acceleration the fuel pump can't keep up with the fuelling requirements from the ECU?

I've seen a lot of people rate the Walbro pumps (225?) and you can either go in-tank or in-line. I'd prefer to go with one that's a direct swap for the original in-tank if possible, any suggestions?