[turbosetch]

Thanks to who ever has some input on this ahead of time.

We have a 2008 335xi 6MT, JB4, CPE downpipes.

The issue is major boost spikes 21+ psi then holding much higher boost then called for. Results in 30FE then 3100 codes.

Originally the car had some power loss and a boost leak at the divert valve, we replaced o-rings at both divert valves, inter cooler hoses, and throttle body. We also replaced spark plugs, due to misfire codes. We then began to have the over boosting issues once the leaks were fixed.

Steps taken so far:

(1) Boost leak check -- OK
(2) Checked for v-bands hitting WGA -- OK
(3) Used known good waste-gate solenoid and swapped with each one on this car -- NO CHANGE
(4) Checked vac tanks and vac lines to WGAs -- OK
(5) Had dealer remove original Dinan tune and flash entire car to stock -- NO CHANGE
(6) Remove JB4 completely -- NO CHANGE


So we are at a complete loss here, the only symptoms I can describe are what seems to be a delayed or slightly slowed spool then sudden spike then control again but at a higher then targeted boost. At idle there is a ticking from the drivers side of motor, I have never heard this on any other 335 but it goes away off idle. Besides the problems noted there are no other codes, no idle issues, drives smooth without boost, etc.

ANYONE who has some solid input on this we would love to hear it and if your suggestions lead to solving this mystery we will send you $50 via paypal.

Thank you!

[Jeff@TopGearSolutions]

It's spiking 21 psi without a tune? From where is the data being read from? Is the throttle full open? Any datalogs?

[turbosetch]

Originally we were data logging with the JB4 system. After the flash back to stock we put a boost gauge on it and the spikes are lower than that but still there and still causing the 30fe code and limp mode.

Throttle was full open until spikes on the logs then it would shut slightly. Big spikes were logged pre-manifold so not manifold pressures.

[Tuesday]

Sounds like a wastegate issue to me. If the lines and actuators are good, have you checked the vacuum pump?

[rader1]

Could also be that the wastegate actuator arm is sticking or binding.
Is there any way for you to log requested boost, actual boost, req/act WGDC?

[PR3CI5N]

Since you have a JB4, just do a datalog and send the CSV to T. He'll def solve your problem.

[jayk877]

Originally Posted by PR3CI5N

Since you have a JB4, just do a datalog and send the CSV to T. He'll def solve your problem.

+1

[JamesM3M5]

Next thing to check is operation of the wastegate actuators. Sounds like one is sticking. Remove the rail that holds the solenoids so you can move it around to view the WGAs and rods. The front is hard to see but you should be able to see at least the rod moving. Get the motor hot (drive), pull in, and use a vacuum pump to pull vacuum on each WGA and watch for binding. I've seen one sticking bad enough that it wouldn't close the rear turbo WG and had underboost codes. It is possible that one is sticking, finally shuts (watch WG duty cycle in logs), then sticks in the closed position. Remember that the WGs are always open until vacuum is applied to close them and generate boost. Since it's not a software problem, I'd put the JB4 back on to log, too.

[itsmeek]

Just a general question (i'm sure you know this already) here- isn't 21psi VERY UNSAFE for that car? I'm thinking that anything more than 18ish is dangerous. I wouldn't drive it if you're getting those type of numbers. Just sounds to me like your wastegate actuators are sticking. Did you replace this? Another thing could be that you have pinpoint leaks in your vacuum lines. Have you done a vacuum line pressure test?

[pimple]

Have you checked the diverter valves? Ticking on the driver's side and overboosting could be pointing there, IMO.