Spiking too much boost + bouncing RPM idle - Please Help!

[TitaniumSpeed24]

My car has been boosting more than normal lately, mainly on the spike. I have a boost gauge so I know I'm not inventing something and it also feels faster - it has been spiking around 9 PSI on the highway for the last 2 or 3 weeks or so. It spools around 5 PSI consistently in 2nd and 3rd gear. As well, the idle has gotten really rough during the last 3 months or so. The RPMs bounce up and down at idle and a lot of times when I pull it out of gear while braking, they will dip to 100 or lower and the engine almost cuts, then they bounce back up again. I have heard this would be due to a boost leak but I am not sure if this is the case. Could it possibly be a bad wastegate due to the high boost spike? Today on the highway I hit the gas moderately hard in 5th gear (not wide open, maybe 3/4 throttle or so) to pass a truck and the turbo spooled up and then the car made a violent shake from the engine bay as if it would have died had I not been in gear. This is the second time this has happened before but both have happened on the highway within the last week so I'm attributing it to some sort of boost related problem. Please help!


EDIT: I just realized what the problem for the ridiculous shudder might be - fuel cut? since hte car is boosting higher and it only does this shudder in 4th and 5th gear (the gears where max boost is achieved) I'm guessing its probably fuel cut. Maybe? Ahhhhh help!

 

[Butternuts]

I just had to replace my WGA and the problem i was having was very different than yours. I would boost nice and hard for about 1 to 2 seconds then it felt like the boost just disappeared and I would hear a high pitched whistle / sucking sound. You can check your WGA by blowing into the vac line attached to the WGA... if air goes in its bad. When my WGA was bad my idle was also very funky. It would idle low and then out of no where it would dip down and almost die.

 

[MSP2024]

i had the same problem when i had a boost leak it would spike at 10 and the rpms dropped low and sometimes died

 

[TitaniumSpeed24]

so any idea of where to look for this leak? I need to fix this problem and I'm not sure what to do. My neighbor who is very knowledgable about turbos after his two 500 whp boosted m3's and he said he thought the clamps looked ok and there didnt seem to be any cracks. . . Where should I look for this problem?

 

[FunkyBuddha]

Boost leak will cause those rpm dipping
-start at intercooler pipes
-hose where the bpv is connected to one of the pipes
-have someone rev the engine and hold your hand along the piping and hoses and see.

 

[Houston]

Boost lag

I have had a problem with boost lag for quite awhile now. Most of the time The boost will not kick in till around 5000 rpm's, before the boost kicks in you can feel the car holding back quite a bit. Anyone come across a problem like this? My boost guage reads 6 Psi
throughout the rpm's as if it were functioning normal, kinda weird