PCM for less tune
I went with Ion this time.
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What seems to happen more often than not is simple things like the throttle blades are not opened enough (causing idle surge and a seeming rich condition as the car is basically choking as the IAC motor cannot open enough to get the necessary idle air into the engine), or guys do long tube installs and get the O2 wires melted to the headers, or make their own O2 extentions and don't soder the wires and crip the connections instead, or what has been happening a lot is the coating on headers bake onto the O2's and ruin them by making them read lazy and fool the PCM into thinking it is lean when it is not.
Other issues I have seen have been things like timing chains a tooth off on cam installs, vacuum leaks, dirty MAF's (this is a big one too and causes many cars to run lean, a simple MAF removal and spraying it down with cleaner does a world of good and should be normal maintainence), clogged cat converters, misadjusted fuel pressure regulators, bad/misized injectors, ill placed MAF sensors and blowoffs on supercharged cars, and overtightened roller rockers.
With so many mechanical issues possible, even the perfect tune cannot overcome simple mechanical mistakes. The problem is, you try to help someone diagnose these problems and you get the typical "there is no way I did something wrong when I put it together" isntead of the "yes, let me check that"
I've done so many of these cars (thousands) that I have seen it all. And most times the problems are fairly easily diagnosed and exhibit the same symptoms every time and each mechanical issues seems to have it's own specific symptoms. So many people though think that it has to be something in the computer as that is the "easy" fix. Thing is, the GM closed loop system is more in control of part throttle than myself or any other tuner. It uses the O2 feedbacks and MAF readings to adjust it's fueling. Yes, I set up the injector constants, and VE tables to help get the GM closed loop system a good start so it has to adjust little if any, but the bottom line at the end of the day is even if I am dead on, if the sensors feed garbage to the PCM the PCM will adjust with closed loop and override anything I do. Also, to all those who seem to think that a certain smell means you are rich and have never put the car on a wideband.... A car with a big cam like a 306 Comp cam and no cat converters.... WILL STINK, but is it running rich, no. Slip her onto the wideband and you will see 14.7 to one all day long.
Have I ever had a program that was not right, sure, with as many as we do, ALL of the big name tuners have made a mistake now and then, but 98% of the time, sensors, mechanical issues, or simple adjustment to things like throttle bodies and TPS sensors are all it takes to get everything dialed in. Take any two hotcam cars with the same modifications and put the same program in them and they will be within 3 to 4 % of each other every time, but have the one car with the rockers overtightened by a turn and it will change drastically.
What seems to happen more often than not is simple things like the throttle blades are not opened enough (causing idle surge and a seeming rich condition as the car is basically choking as the IAC motor cannot open enough to get the necessary idle air into the engine), or guys do long tube installs and get the O2 wires melted to the headers, or make their own O2 extentions and don't soder the wires and crip the connections instead, or what has been happening a lot is the coating on headers bake onto the O2's and ruin them by making them read lazy and fool the PCM into thinking it is lean when it is not.
Other issues I have seen have been things like timing chains a tooth off on cam installs, vacuum leaks, dirty MAF's (this is a big one too and causes many cars to run lean, a simple MAF removal and spraying it down with cleaner does a world of good and should be normal maintainence), clogged cat converters, misadjusted fuel pressure regulators, bad/misized injectors, ill placed MAF sensors and blowoffs on supercharged cars, and overtightened roller rockers.
With so many mechanical issues possible, even the perfect tune cannot overcome simple mechanical mistakes. The problem is, you try to help someone diagnose these problems and you get the typical "there is no way I did something wrong when I put it together" isntead of the "yes, let me check that"
I've done so many of these cars (thousands) that I have seen it all. And most times the problems are fairly easily diagnosed and exhibit the same symptoms every time and each mechanical issues seems to have it's own specific symptoms. So many people though think that it has to be something in the computer as that is the "easy" fix. Thing is, the GM closed loop system is more in control of part throttle than myself or any other tuner. It uses the O2 feedbacks and MAF readings to adjust it's fueling. Yes, I set up the injector constants, and VE tables to help get the GM closed loop system a good start so it has to adjust little if any, but the bottom line at the end of the day is even if I am dead on, if the sensors feed garbage to the PCM the PCM will adjust with closed loop and override anything I do. Also, to all those who seem to think that a certain smell means you are rich and have never put the car on a wideband.... A car with a big cam like a 306 Comp cam and no cat converters.... WILL STINK, but is it running rich, no. Slip her onto the wideband and you will see 14.7 to one all day long.
Have I ever had a program that was not right, sure, with as many as we do, ALL of the big name tuners have made a mistake now and then, but 98% of the time, sensors, mechanical issues, or simple adjustment to things like throttle bodies and TPS sensors are all it takes to get everything dialed in. Take any two hotcam cars with the same modifications and put the same program in them and they will be within 3 to 4 % of each other every time, but have the one car with the rockers overtightened by a turn and it will change drastically.




