Just finished a cam swap(GPI VVT2) on 2010 L99. I have a Tuner working on the tune now. I have asked him the question already but he has not gotten back to me yet. He usually takes 24-28hrs to respond. So I thought I would pose the question here. Car starts and is idling really rough which I expected. But when I go to apply the breaks they are rock hard. I had to step on them just to get it out of gear and if you barely let them go it will start rolling. I have done some reading and a lot of people mention that it could have something to do with the tune. I have attached a copy of my logs. I'm curious if I'm just being impatient or if I should start looking at something mechanical like a vacuum leak, master cylinder, etc...
I have experienced this a bit during the tuning of my truck. While I don't know the exact cause in the tune file, it is usually indicative of low vacuum (or a failing booster). Look up the recommended idle for you cam and make sure you are in that range. The next thing I would think is either running too much or too little air / fuel at idle. I don't have my tuning program here, so I cannot look at your file. If you have a rough idle and hard brakes this could also indicate a vacuum leak somewhere...
Also, if the cam is too big, you loose a lot of low end vacuum. on the older cars we would either install a vacuum pump or a chamber to increase volume.
When your car breaks you need to fix it, when your car brakes it slows down. They sound the same but are different words that mean different things.
Now, idle timing in that log is 10-11 degrees, raising it to around 20* will increase idle vacuum. I have no idea what's in your tune file because you didn't post one.
And who knows how big the cam really is, the vendor thinks they are being clever by not publishing duration/lift specs.
Well as it turns out I'm an even a bigger moron than blindsquirrel is proving me to be by correcting my grammar. "Broken" clip on "brake" booster vac sensor hose. Replaced clip and I'm back in business.
Reply With Quote
