On my way home tonight, I decided to do a quick pull ( I rarely floor it, let alone hit more than 5 psi) and in 3rd gear on two separate occasions at about 5000rpms, the car would feel like a bucking bronco or I just hit something. The afrs are fine on normal driving and was a little bit lean when I would get into it a bit. I am assuming that the "hitting a wall" feeling I got was from fuel cut from over boosting, due to the cold weather or at least that is what I hope it is. My main question, is that I do have a tune, but I am using a MBC instead of PCM control boost, so should I adjust my MBC if the weather is going to stay consistently cold? I figured the car would just pull crazy timing if I over boosted, but maybe I just hit WAY to much boost that the pulled timing didn't help? Any help is appreciated!

 

do you have a tactrix cable to log the car? when my car started hitting walls it was because of a couple things each time. the first time this happened, I needed new spark plugs. after modding, it started happening more (i've got a really long thread about it), and it seems to be some phantom knocking going on. the car was seeing knock, pulling timing, and the car just felt like it fell flat on it's face when it would. if you can do some logs, that might help see what's going on.

as for the overboosting with an MBC thing, I don't know much about that problem so i'll let others comment. i've got a grimmspeed BCS, so that's not an issue.

good luck with the issue

 

Check that the intake snorkle is clipped to the rad support properly. If the clips are missing it will lift and choke airflow causing the exact issue you are describing.

 

Huh?

 

I had this happen before and was very worried. If the two clips on the intake snorkel that hold it down to the radiator support are missing, it can lift while in boost and seal up against the hood feeling like you are hitting a wall.

 

If you are running the stock intake, there is a snorkel that attaches to the body under the hood. It directs air to the intake. It is held down by plastic rivets. If those come loose, the snorkel can move, choking the engine.


OP, you are most likely hitting fuel cut. Colder weather=denser charge and you are probably running more boost. Turn the MBC down some, and log the car to make sure you're safe.

 

try turning the boost down and check that MBC, I have had my boost change 5 psi by itself before

 

I had to turn my boost down by a couple psi because of the colder weather, i was having popping issues but not like hitting a wall. I turned my boost down a couple psi and regapped my plugs and it fixed it. hope that helps

 

If it feels like you are hitting a wall, it's boost/fuel cut (which ever you want to call it). Do you happen to know what it's been set to in the rom, and what boost you actually hit when it cuts?
Boost/fuel cut is load related, so any change in air density can have a big effect on the load the ECU reads.

 

overboost protection or vacuum leak

 

as dumb as this may sound my evo did the same thing when my rear o2 was bad,switched her out and its good too go

 

Sorry for the lack of update guys, but I have good news...

I turn the MBC down a full turn and that helped a bunch, but it was still breaking up a little bit up top so I went over to No Limit. Manny and I datalogged and the first few pulls, nothing happened the car was fine, a little lean, but fine. Then, on the way back to shop it started breaking up, so we logged again and still nothing. Manny added a little bit of fuel and bam every problem went away and my afrs are much safer. My injectors blip 90% duty cycle but average about 87%, so I will be getting new injectors as I plan to go further and possibly tune for E85 in the spring. As of right now the car is running smooth with no fuel cut or break up issues anymore.

 

that does make sense though as the engine would be reading the afr correctly