I am working on 2 camaros one is a 87 z 5.0L tpi,auto,342 rear ratio and the other is a 91z 5.0L tpi, auto,273 rear ratio. Both seem to run fine until you reach around 110-115 mph and then it's like the fuel shuts off and the car surges violently untill you let out of the throttle. Both cars pull really hard to that point. Also noticed that the 87 doen't seem to shift into od, but seems to stay in drive and won't shift up also it shifts fine anyother time. Both cars have new ecm's and the 91 has new injectors as well and both carry about 44-47 psi on fuel pressure at idle. I have never known an f body with a speed limiter. Any idea's or help would be great.
Thanks in advance.

 

all cars from the mid to late 80s on had speed limiters, its illegal to let a car go faster then the tires it comes with are rated for.

Since auto markers are to cheap to put Z rated tires on cars, they only go as fast as the stock tires are rated for, all tires have speed ratings.

 

I currently own a 91 z and this car will go well above 130 mph and I also owned a 90 formula and that car would also travel well above 130 mph also owed a 91 1le and it would do well above the 130 mark as well all these cars were stock so I don't understand why these two cars would have speed limiters.

 

F-bodys that were factory equip'd with Z rated tires are not speed limited. Unless you consider 254/255 MPH as a limit . Many that came with S and H rated tires are speed limited.

Note that not all f-body's have a speed limiter. So readers, save the comments about how yours could easily do triple digits and were not limited.

Can check the calibration for the speed limit they are set too. The 112/115 MPH values are common. The ECM limits the speed by shutting off the injectors (fuel cut).

As for the 700R4 doing a WOT shift into OD. Again, various f-bodys were set up differently. Some are capable of a WOT shift into OD, while others are not. While others (such as mine) have both the speed limiter lifted along with the transmission modified to allow WOT shifts into OD.

RBob.

 

Ok, say I buy into the whole speed limiter idea is there anyway to know for sure that's the problem? If so how do I undo the limiter?

 

Well you have to buy into it cause it is real and all the fault of lawyers who blamed letting cars go 140+ on 85MPH rated tires were the fault of every high speed accident. And soon became a slam dunk case for big money, so things changed.

Cars only go as fast as the stock factory installed tires are rated for, and maybe a bit below sometimes.



And its in the computer chip.

 

So all I have to do then is replace the computer chip with a new one. Then the top speed will be only limited by the car not the computer. Any recomendations on a new chip for a stock f-body?

 

you must DIY if you want your monies worth, the chips you can buy from name brand places are basically a ripe off.

goto DIY prom section

 

Thanks for all the help I contacted TPIS and for 100.00 they will take care of my problem and make some other adjustments as well. But I think after reading DIY Prom I am going to just buy the stuff and do it myself. Heck I know enough people around town with f bodies I might even make a couple of bucks LOL Thanks again.