I have a 90 IROC. At WOT the tranny will downshift and the engine rmp will rise to about 4000 rmp and stay there. It wont shift into the next gear. I have to finally let off the gas a little for it to shift. Also when it downshifts and gets to 4000 rmp it feels like the car is just coasting and going no where....Whats wrong??

 

GM has a Police PKG 3-4 shift valve train that allows WOT 3-4 upshift, it is #8673948. You are experiencing a very common complaint for these. You can also go with either a midified or aftermarket TV Plunger but the results ar un predictable as to the change you will get. As for holding at 4000 feeling like neutral, I can't speak for your engine but TPI setups often peak out lower than what you would like although I would expect it to be closer to 5000. Perhaps a check of the fuel system, including the fuel filter and if possible, scoping the fuel pump to evaluate the condition of the internals is in order. It is not uncommon for problems in this area. Don't expect to see much by just doing a basic pressure test and volume test unless you can do it under the same conditions.

 

Thanks for your help. I going to put in a new fuel pump sometime soon. The car wouldnt start a while back because of low fuel pressure. I put in a new fuel filter and the car started up fine but then this problem happened. Putting in a new fuel pump should make the engine rmp go much higher so it can shift like normal and get the power back.......Thanks!