Ive been having this problem for a bit now. I have an 05 RS, and it idles fine, no CELs going off but anytime i go to do a pull, it hesitates for a second, then starts to go. Once it gets around 5k rpm, it sounds like a backfire and the car starts chugging and never makes it passed 15psi. I pulled my fuel pump, checked the grommets, and made sure everything was plugged in and straight, and it fixed it for about a day or 2. Then randomly it started back up. Ive changed plugs, which didnt do much.

Im on the factory tune right now and using the HKS blow off VTA, which I know is typically a no-no, but thats how it came and Ive had it on for a while before the problems started. The only other mods I have are UICP, LICP, Downpipe and catback, Still have the Cat on there. And an intake.

My first guess is something in the ignition. Time for new coils maybe? I was also thinking about timing. Any help, or suggestions is greatly appriciated! Thank you!

 

might not be what you think..run a boost leak test.

 

check the cat aswell.

my buddies car slowly lost boost to the point of no boost at all. no CEL or anything. ended up the cat was plugged/burned up from running so rich with a VTA BOV. get it tuned if your VTA.

 

oh yes thay cat can be clogged up and hold you back alot!

 

What plugs are in the car and at what gap?

 

Right now, I have BPR8ES gapped to .026

 

+1 on possible clogged Cat. but usually if its clogged it wont let you boost that high. Could also be a MAF problem.
Running Stock Ecu/Turbo? kind of sounds like a tuning issue.

 

Those plugs may be to cold. Those are 2 steps colder I believe. Also, lower the cap to .024 or .022.

 

I know it sounds strange but check your camshaft sensor. When these go out or act up they tend to let you drive normally just fine but when you try and boost the car runs like crap.

 

Plugs, boost leak, running rich, stock tune.

Dude, there is plenty you need to fix on this thing. Do what everyone is suggesting (tune, regap, get recirc or tune for VTA) and see where you're at. I had a similar problem that ended up being a **** tune and dumping fuel. Some reason my ecu went to a safety map on me.

 

Yeah, theres plenty on my to-do list. All part of the fun...I guess. I regapped the plugs to .022, and tomorrow Ill see about checking the cat. Thanks for all the help!

 

yeah easy way to check is just pull it out, and look into it ,and then go for test drive with it off and see how it boosts. its gonna be loud.. but sounds sick!

 

I would gap at 0.020, make sure the AFRs arent less than 10.5, then check wires, coils, etc. No codes though?

Aaron

 

I havent had it scanned for codes yet, but theres still no CEL. ANd the bolts holding the cat on are pretty rusted and are pretty tough. Im gonna replace it with a test pipe I have and hopefully thats all It needs.

 

anybody else concerned with the VTA hks? i have always understood these to cause problems, especially without a tune