My car has been acting a little weird lately and I was just curious what some of you think. Some days it seems to be powerful, other days it seems to bog down a bit. Sometimes when I hit the gas it hesitates before getting the nice oomf. Could it be the spark plugs? I've only got 5k on the new plugs, so could that really be the problem? Should I reset my ECU for the new climate (just moved from upstate NY to Northern VA)?

Also, my BOV makes a whistling sound when I'm between -5 vac and 1psi and I shift. Is this normal?

 

diff temps/elavations will def make a diff in your ecu.. I'd go with trying to reset the ecu first, then work from there.

 

Sounds like it could be alot of things. Did you gap the plugs correctly? I doubt that is it, sounds more fuel related, like you are bogging. Have you tuned your setup yet?

BOV whistling, dependent on the BOV is normal. Could be just the BOV releasing the excess air, but not with a full oomph. Try adjusting the screw on the BOV and tightening it, if that is giving you driveability problems.

 

My car does that sometimes too and it seems to be related to the stupid MAS. My car was running fine but this past weekend I was driving on the highway in the pouring rain and my intake sucked up water and got the MAS wet. I had to take the whole thing off and dry it out to get the car to run again and now it's been doing what you're describing ever since. That MAS is very sensitive. I was playing around with my filter location when I first installed my turbo and the car would bog with the filter farther up in the engine bay, but would be fine with it down in the fender getting the colder air. I finally found a location that worked best and left it there, but I had to reset my ECU after moving the filter in order to get the car to stop bogging like that. I'm pretty sure that's what I need to do now to fix the problem again, but I havn't had the time. Probably do it tonight when I get home. I would try that and see if that works. I've also noticed that changes in the weather make the car run differently as well. So that could have somthing to do with it.

 

Depending on temp and humidity, my car does the exact same thing. When its really nice out in the morning (50F or 60F and low humidity) my car flies. After it warms up in the middle of the day (80F or 90F and high humidity) my car will bog down ALOT. What I did was make a little extention to the front of my car so cooler air is getting to the filter. Also, when its warm out, reset your ecu and then let the car idle for a while. Then drive around the block a few times starting out slow, then work up your RPM's once and a while. Try that first if anything.

 

I'm gonna guess it's related to the relative lack of precision in using FMU's to provide more fuel in turbocharging. Does it bog in boost, out of boost or both?

 

Both. And I wholly agree with your FMU theory. I think eManage is in my future so I can tune this precisely.

Plugs are gapped fine, and I'm going to check their condition this weekend. I'll reset the ECU as well and see what happens.

 

spray brakeleen on your intake manifold and injectors where they meet the manifold just to check for any leaks. i don't see how one would easily develop on stock injectors but its worth a try. also check all your vacuum connections and make sure there is no damage on the hoses or anything.

 

What air / fuel piggyback are you running? If AFC, perhaps you can alter air / fuel ratios a tad and see if that works.

 

If you have any way to accurately monitor your AFR (even if you just go do a few WBO2 monitored dyno pulls) you should be able to get a bearing on whether or not it's fuel related pretty quickly. I think it probably is, but it's hard to make a diagnosis like this, ya know?