My car runs very good in open loop. Then when the rpms drop, and it goes into closed loop, it has a small miss, and just doesnt feel as fast. Ive been trying to fix this problem for over a month now after I got my pcmforless tune to no avail. I had it datalogged, sent it to bryan herter, he said I needed maf, got maf, problem still there. I am about to ask him to just tune it to run in open loop all the time. Thats when it runs the best. my question is has anyone else done this? What are the problems, or advantages?

 

Sounds like my problem. After it goes into closed loop , when you jab the pedal does it missfire and stumble, then pick up and rev fine? That is what mine has been doing for sometime now. I have searched this alot and from what I can tell it could be a number of things. Some say that the ICM gets heat soak and to gap it away from the head with some washers. Others say that is it a o2 sensor that is bad. Others say that it is a exhaust leak or vacume leak. LOL So it realy seems as though the problem would be best diagnosed with a scanner that reads live motor stats. Good luck man! Please post if you do track down and fix it

 

Problems, worse gas mileage, needs to be retuned once every 4 months (you could stretch it to every 6 months...), still doesn't fix whatever your real problem is (possible bad o2 sensors). Get it dyno'd in open loop and in closed loop see which really is more powerfull. The RPMs are supposed to drop in closed loop, and you're driving a firebird a "small miss" might just be whats normal for your car, likely you are seeing a little lope if anything. Chances are if you dynod both you'd find closed loop is actually more powerfull. The power curve should be wider which feels slower but in actuality isn't. The reason it feels slower is because your body can't feel velocity (speed) at all, but it can feel change in velocity (acceleration) It can also feel change in a change in velocity even better (change in acceleration). When people drive CVT vehicles for the first time they ALWAYS feel slower than conventional manual or automatic transmissions. But when you look at a CVT vehicle and a comparable automatic or manual transmission in the quarter mile or some other real measurement the CVT is faster. It just feels slower because the acceleration is relatively constant. A wider torque curve has a similar effect.

 

thanks. I have the same prob. camaro kid. Ive changed 02s, opti, coil, wires, fuel pump, maf, and it still does it. It started after my tune. I had it datalogged, and he said everything looked good, except the maf readings were very high, and my injectors were maxed at 5200 rpm. If this new tune doesnt help, then I will assume I have a leak at my header flange.