Author Topic: power loss at 4000rpm  (Read 123 times)

Offline muff1991

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power loss at 4000rpm
« on: February 11, 2019, 12:16:59 PM »
hi all, car seems to boost up as normal, but as soon as it hits 4k (ish) it literally cuts the power, or shall I say reduces it dramatically for a good few second accompanied by the DV psshh as if ive just let go of the throttle (i haven't)! if i keep the throttle pinned.. the power will all of a sudden come back around 4.5k (ish).. and rip the last bit to red line.

I have VCDS but am new to it, and don't know exactly what to start with.. - i defo have no codes on auto scan

This issue started (or i noticed it) the same day i noticed my cold start issue... depending on temperature outside, either engine starts then cuts out, or engine starts and runs but has laggy throttle until 2k revs then picks up normal. (obvs until 4k haha). I'm sure its related somehow.

any advice is appreciated.

Offline Pudding

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Re: power loss at 4000rpm
« Reply #1 on: February 15, 2019, 06:43:37 PM »
Data log a 20 minute drive from cold, and then chuck the csv file into Excel for analysis.

You can only log 12 channels at once, so do a couple of runs.

On run one, choose these measuring blocks.  I can't remember the exact names of them, but something like :

Engine speed
Fuel rail actual
Fuel rail specified
Low pressure fuel pump
MAF
Boost pressure actual
Boost pressure specified
Intake Air temp
Throttle angle
Lambda regulator

On run 2, go with:

Engine speed
MAF
Throttle angle
Boost Specified
Boost actual
Lambda
Throttle angle
Ignition retard cyl 1
Ignition retard cyl 2
Ignition retard cyl 3
Ignition retard cyl 4

From the data you should be able to spot anything obviously wrong.  See if boost and rail pressure specifieds and actuals match.  The ignition retard should be very small numbers.

Massive ignition retard, boost request not meeting target, big lambda adjustments, fuel rail pressure drops etc can all cause the symptoms you described.
Black Edition 30 with manually selected cogs, a beefier clutch, some extra boost and them Whiteline thingies, otherwise standard.

Offline bobby_fodge

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Re: power loss at 4000rpm
« Reply #2 on: February 15, 2019, 07:40:18 PM »
It's not the clutch slipping and then biting again?

Offline muff1991

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Re: power loss at 4000rpm
« Reply #3 on: Today at 04:16:23 PM »
@Pudding thank you very much for such a full detailed process.. exactly what i was hoping for :-) I only see this post today! at which point.. over the weekend, i replaced the cam chain cover gasket (as you know, I done the job twice) and found out afterwards I couldn't use the same gasket.. i think its a 1 trip pony... sooo small oil leak!

possibly related.. and I have to put my hands up here.. but when replacing the gasket, i only went and found that the bottom center bolt of the cam chain cover was loose! last time i must of twizzled it in with the skinny T30 extension by fingers and when torqueing up the 7 bolts.. i must of torqued the T30 right next to it! felt like an absolute plumb mate!!

Anyway, while doing this, cleaning everything up.. I replaced the VVT cam adjuster solenoid. (the sensor going into the cam chain cover) as someone had broken the electrical plug on it previously. I had temporarily repaired it months ago and the car run great! but with the heat, it was brittle and snapped again. so put a new one in and jobs a gooden.

so with all that said.. this weekend I achieved and replaced:

a new VVT cam adjuster solenoid fitted
an oil leak free cam chain cover
an ECU reset as the battery was disconnected for a few hours
a tiny tiny tiny air leak in the bung on the inlet manifold (part of the Forge PCV delete)

took the car for a drive afterwards, once it had warmed up and cam chain had some oil squirted all over and i gotta say.. it drove perfect! more low down grunt.. power just hits and goes.. traction light was wanting to slap me up side the head, and it pulled smoothly all the way through from 2k - 6k! in 2nd and 3rd gear! It bypassed 4k cut off i was getting like it wasn't even a thing!!!

so I'm pleased to say with a mixture of all those, its fixed. whether it was down to a small boost leak, small oil leak loosing crank pressure, dodgy VVT cam adjuster solenoid or what I personally think most of all... is a good ECU reset! whichever the cause, if not a bit of all.. its done and I'm very happy.

my only concern or doubt with the fix.. is my cars been acting very weird in the colder temperatures and the power at 4k could sometimes be intermittent depending on warm or colder conditions. This weekend after the fix, when i drove it was 12 degrees Celsius. so come the colder whether in the next week or 2 i will tell better. no doubt ill be back for more help otherwise haha. (although the way it was behaving.. its fixed  :happy2:)

@bobby_fodge thanks for the suggestion.. as always I'm more than happy for anyone to throw ANY clue or ideas around as it all helps with diagnosis. but the clutch is feeling solid (for now  :signLOL:)

thanks again for the input.. @Pudding I am still going to do these logs once i get the chance! just to see if everything is behaving anyway.