Hey Guys,

I used a tuner here in Ft. Worth that has given up on my car, and blames the problems on wiring shorts. I picked the car up and it runs fine. Every once in a while (20 miles or so), the car will start sputtering like it is going to die. You keep giving it gas, and it eventually catches and takes off. I just drove the car back and forth to the office today. 80 miles roundtrip and it used almost 8 gallons of premium. I think the problems I am having with the O2 sensors is the fact that the tuner is drowning my car. Before I go and blast the guy, I just thought I would ask. In a supercharged car, if you're driving sanely and cruising on the highway - shouldn't your gas mileage be pretty normal (18 - 22), not 10!!!

Oh yeah, I know he tuned the driver's side pretty close on the dyno, but not the right side. The driver's side chrome tail pipes look fine. The right side are turning the chrome a tan or gold tint. Also, the exhaust just simply SMELLS like gas.

Thoughts???

Dave

 

Can't really give you any advice without hard data.

These cars pretty much tune themselves at part throttle, so I would guess there is more to your problem than just the tuner.

I would start by looking for bad injector wiring.... Make sure you are getting a good clean pulse on all connectors.

 

To answer your question on gas mileage. My Magg'd C5 gets 30+ on the highway, when I stay out of the boost.

 

Check your wires. I had a similar problem happen to one of our cars, the wires looked good from the outside, but when I tested them on a meter, it was a different story.

Rick

 

Rick,

By "wires" do you mean the plug wires or the O2 sensor wires?? The plugs and the plug wires have all been replaced. I took it out again last night. The car ran nice and smooth as long as I didn't get into it. When I punched it, the car just screamed - LOTS OF SMOOTH WICKED POWER!! As soon as I let off the gas, it started sputtering and it took about a minute or two for the car to smooth out. I mean, it gets down to almost stalling out no matter what you do with the gas pedal. It cleaned itself up in about two minutes or so, and then I hit it again. Same great power, same sputtering and stalling afterwards. After it smooths out a little to where it responds to the gas pedal again, then you can rev it a little bit in neutral and it acts like it is blowing itself clean and runs smooth again. The tailpipes are caked with black soot after only 80 miles. I think I will let another tuner have ago at it. It really sounds to me like the car is running so rich that it is just fouling things out under boost.

Dave

 

Seems like quite a different story now. Your first post and this post don't match up at all.

Anyway, the wires I was talking about are the injector wires. Spark should also be checked.

I would also stay out of boost until you get all the part thorttle issues worked out. People wonder why stock motors blow up and then everytime I talk to someone with a problem they have some story about how the car was running funny and then they got on it to see what it would do.

 

Ok, yeah alittle different now. Here is what I am thinking.

Your tune is way off as you come off the throttle hard. It sounds like your trims wind up going in one direction so far, that it takes a minute for them to come back and average out back to where they were. Its worth a shot to look at.


Rick

 

Mine is a weekender and my mpg is 12.5 according to the DIC!!!

 

Thanks Rick,

Sorry to all if my original explanation wasn't clear. It is frustrating how a car can run so smoothly, have tremendous power when you punch it, and then just crater for a few minutes after the hard run. However, I think you have come to the same conclusion I did. It is the tune. The car simply runs too strong under boost for it too be having mechanical or wiring issues. I will take it to another tuner this weekend. The last guy had a small fire in my car while on the dyno and shorted out the PCM. After repairing that, he shredded a FLP level IV transmission with less than 20 miles on it by forcing it through the gears when the codes were telling him it was in a safe mode. All in all, this guy had my car for over 6 months and charged me $2k (to repair damage he mainly caused) on top of the $500 for the tune that he didn't finish. BTW, the fire in the engine bay SUPPOSEDLY was caused by oil from the a/c line. The a/c was vacuum purged when we removed the motor and had been open and dry for 5 months before the fire. Unfortunately, you can't recover from sloppy shops. You just pick up your toys, pay the bill, and try to find someone that knows what the heck they're doing.

Live and learn.

 

If one side of the engine is running a lot worse then the other then its
probably not a tuning problem. I would datalog your car the problem
should be fairly obvious if its as bad as you say it is.

INTHERED