Slow To Rev After 3000Rpm

[Trex]

Hey guys, so I've put up with the problem since I bought the car but after writing it out I see how f**ked up it really is and it can't be normal.

My rs4 2.5T auto at light throttle it will rev to 3000rpm easily then stay there for a few seconds then go through the rest of the rev range slowly then reach 5000 and take off hard. Kind of like driving on flat ground then reaching 3000rpm up a steep hill and you reach the crest at 5000rpm

I've tried stock boost and 10psi but it doesn't make a difference. I was told it's a tuning issue, and i do believe him but I'm sure they didn't drive like that from factory because my old commodore had heaps more power down low. an old 90's Camy beat me until I reached 5g

I took the front drive shaft and the fuse and noticed If I do a burnout with no brake it will slide then take off slowly like it has traction controle. Even at speed and throwing it into a corner it will do this.

I've been searching for months for answers and I'm now at my wits end.

I've got a 3" from turbo to tail with split dump

I've replaced o2, coolent temp, afm, plugs 1.0 & 0.8, coils.

[Duncan]

That does sound like a boring old misfire, particularly if you hearing it popping a bit at the same time it stops accelerating.

From your post you have already spent a heap of money swapping random stuff, why not take it to a workshop with a dyno? They can swap all the bits they need to without you buying and trying each thing.

If you want to keep trying the swapping you could always change the CAS and ignitor and resistor packs depending on what your engine has.

[Trex]

I don't hear any popping anywhere in the revs. Sorry should have said that.

I took it to Jez who found a fault with the afm and did a leak test while it was on 10psi. I do believe him when he said it needs a tune to fix the issue but when I changed the boost to the stock 2 stage the same problems occurred.

The stuff I changed needed doing anyway, just thought I should mention what I've already changed.

Could it be VCT not working properly? Or possibly hitting r&r even on stock boost? The power loss while trying to do a burnout is weird as they don't have traction control?

I need it fixed because keeping up with traffic can be a pain and I need to drop back gears and sometimes it will take off on me and is dangerous.

[Trex]

How do I check the cas, igniter and resistor packs Duncan? I've read posts where ignition and fuel pump are mentioned quite a lot. But no one posts after they fix the issue.

Jez also mentioned he removed my knock sensors and the only other fault was the afm which was changed also. I don't want to keep bugging him because I've done that enough

[Sinista32]

1. Listen to Jez

2. Type of aftermarket ECU ?

3. Is there a reason it can not related to the Transmission, Transmissions ECU or Solenoid ?

Keen on burnouts in a Stagea hey .......

[Trex]

Not keen on burnouts, I would have bought a v8 if I did haha. I noticed it when I drove up a really steep hill in the wet and kept my foot down. It spun then lost power like it had TC. I then threw it into a corner and it did the same thing. I thought it might help diagnose my problem.

I trust Jez, he knows his stuff and has dealt with a few friends cars. But I can't afford an adaptronic and a tune to fix my issue

I was thinking it could be a tranny issue, the auto is in the ecu and never showed any codes, where's the solenoid for the auto?

[Sinista32]

no mention of ECU so I assume it's stock.

You've reset the ECU's or had them reset and checked for new codes without success

I'm no mechanic so I end up taking my car to the shop to identify and rectify. after I provide as much info as I can.

and yes if money is tight it's not easy I know.

Just from what info supplied above gave me a suspicion it may be more transmission related.

A tranny service wouldn't go astray for a few hunji dollars but could also not identify/fix issue.

(3.8lt auto commies spin rears easily - hence bogans fav drug delivery vehicles)

[Jezboosted]

What about this fella here, Isn't it responsible for determining throttle position and based on afm readings - giving the correct amount of fuel ?

Edited July 3, 2013 by Jezboosted

[wolverine]

Nistune and give it back to Jez.

[Trex]

Thanks for the help guys,

I'll be checking my TPS voltage this afternoon,

I can't really check VCT, can I put it on stands and start it put it in drive then use the throttle from the engine to see if its clicking at 1500? Or is there an easier way?

And I'll search how to check my CAS

[Trex]

Can't nistune my hitachi auto ecu wolverine

[wolverine]

Saw the pic of the S2 TPS and assumed you had one.

[Trex]

Haha not my engine. Mine has 2 plugs coming off it. I'll check fuel pressure too.

[Trex]

Could it be a vacuum leak?

What should my vacuum boost be at idle? Or do I need to check and replace every vacuum hose in the system? (I have no idea where they all are)

[Trex]

Doing more research, my 0v300 ecu will trigger r&r anything above the stock 5-6psi under 4500rpm which makes sense why it feels like a flat spot.(will hit 6psi stock) But doesn't make sense why I picked up very noticeable gains under 3000rpm.

Or/And

the exhaust has made a noticeable torque decrease while increasing the stock boost because it flows better.

Either way I don't think I can fix the problem without a tune or trying a stock exhaust.

[Scriblez]

Hey OS80RN, I had the exact same issue mate, got a tune, all fixed.

Definitely take Jez's advise on this one mate.

[Josh080691]

It could be that the car was tubed before and parts have been replaced etc

[Josh080691]

Sorry early post""

They could if removed parts since last tune, thus making the car run rich or even lean causing the so called problems. I suggest a tune will quickly and efficiently resolve ur problem.

The ecu may be tuned already which will be the cause to your problem.

[Trex]

So I've been doing some driving and changing/checking things.

1. Boost T is coming loose.

I turned the T in 2 turns and the turbo spooled quicker, Had come half a turn loose again after 1 day so the turbo started to lag.

The T must like a certain position because it eventually went back to where it was, 2 turns looser.

2. The auto is getting confused.

Manually changing gears from 1 - 2 - D had a big improvement on getting passed the 3k flat spot.

O/D and Power didn't have any affect on the flat spot.

#2 would explain why it was happening on the standard 2 stage boost

I can now feel the small missfire at 3k on 10psi. I'll change plugs,clean AFM, box oil and i should be good to go.

Thanks for all your help everyone

[Duncan]

so.....?