As described.

There were no mods done to the car from the time it was running well to the time that this started to occur.

Everything feels like it's a go until I hit about 18 or 19 psi. The car shudders (like repeated misses), will not hold boost, and acceleration bogs down.

I have checked the following based on what I know, and some searches:

1. Tried a different BOV (the 03 stock BOV which still works but didn't fix the issue) - But I'm currently using the Mits metal JDM diverter valve.
2. Put the EMS on pass through mode to see if it was somehow tune related.
3. plugs only have about 5 or 6 k on them (and car ran great on them a while back during 1/4 mile runs. they are an 8 heat range)
4. I turned the Halman BC down and the car ran solidly at about 16 psi.

The car is cammed, stock turbo, TBE, Walbrough, and a few other things like lower IC pipe, IC. Nothing radical, and as I mentioned. the problem just kind of popped up one day.


I'm starting to suspect the stock wastegate actuator because of the predictability of the problem

on the other hand:

Would a leaky connection or hose cause the shudder once it reached the "critical pressure point" ?

In the past I have been able to hear any leaks that caused that noticeable of a problem.

I am planning a boost leak test - got to get/make a tester though.

Thoughts or ideas?

thanks

 

Bad ignition coil. Had this problem myself. I was fouling plugs far to often.

 

if its not holding boost then your probably leaking

 

lol a friend of mine's car did this. Turned out we left the blow off valve disconnected. It would build a few pounds then just shut down and tried to stall.....

 

First thing to check if you have the stock airbox and snorkle... Make sure the snorkle is fastened down properly, if it can flop around, it can get sucked up under the hood.

Second thing to check is just replace the plugs, if nothing changed then the plugs could have crapped out.

Third thing to check is make sure the car isn't running REALLY rich, yeah surprising eh? You can get bad misfire if the car is running too rich also.

This is over and above the typical checks for broken/cut vacuum lines, kinked vacuum lines, loose or other damage to the intercooler pipes or couplers.

What are you using for engine management? Is it an intercept device for the stock ECU? Has the stock ECU ever been reflashed? and so on..

 

+1 Had this one get me. Make sure you have the two push pins installed in the snorkle.

 

yeah actually good call... i almost forgot about this one. It plauged me for nearly 3 months!

 

Plugs are cheap and easy I'd start there.

 

all of these are very good!!! just keep searchin it will take time but you will eventually figure it out. also check fuel pressure.

 

It sounds like compressor surge but ... Change the plugs and boost leak test the car first

 

misfires? check the plugs.

 

outcome?

 

Thanks for the responses - I checked back a few times but didn't see any responses. It shows that I'm subscribed, but I didn't get any notifications, and there weren't any that my filters got. Our email server must be catching them somehow - some thread notifications are getting through. weird.

As far as the problem

1. Plugs look good - I'm running NGK 8's - but they are a nice even tan everywhere on the electrode area.

2. The snorkel has been pinned down well throughout.

3. I'm using a UTEC - but have not done anything to the map(s) since before the problem occurred. (I though it was possibly an electronic malfunction - but I put the UTEC in pass through mode and it still did it. I did not actually remove the unit from the car, so I guess ultimately, it's still possible - but I kind of doubt it)

4. Haven't made/bought a tester yet, but that's next.

I took the Hallman BC off the other day but could <edit: not> find a problem. The only way I could test it was to run the boost down to around 16 psi and it held the boost steady there - so I'm moving on to check other areas, at least for now.

Right now the main suspects are:
1. a boost leak somewhere
2. or the wastegate actuator.
3. The UTEC Boost sensor <edit: Leaking> (not using it for closed loop BC, since I have the Hallman on the car, but it is in the system).

(I'm going to log to see what the problem looks like in the logs - just haven't had the time or my laptop at home when I had the time.)


The important thing to remember is one day it just started happening. No Mods, Tuning, or anything that I can think of that would affect it.

ONE MORE POSSIBLY RELATED SYMPTOM:

I noticed on a few very windy days last Spring, that the car would absolutely stall out for a split second, right after beginning to drive, and then regain power. Like the wind caused a pressure drop inside the airbox or something.

It may not have had anything to do with the current problem though. I never did figure that out.

Thanks again for the input

 

Could this possibly be a sympton of fuel cut? Not sure how much the temps have changed there, but temps here are about 20 degrees cooler than usual, which could cause you to run too lean and hit fuel cut. You may need to rescale maps...

 

I don't think so. When I've experienced fuel cut in the past is was more of a single loud thunk with an ensuing loss of power.

I'll try to log tonite or Thursday and post what I find out.