any ideas upper RPM seems good but off idle to about 2k it seems like it bogs or hesitates. i can spin the tires a little (2.73) from a stop right after i start it. but like when i get off the high way i cant ever do it. car has 185k new motor with less than 1k stock rebuild. new opti, fuel pump, any ideas would be great. thanks in advance

 

Maybe the heat is burning up a wire - probably would happen throughout the entire RPM range, but maybe it just isn't very noticeable in upper RPMs..

 

Mine acted the same way stock. Ran strong until warmed up, then it just didn't have as much gumption. Put in a 160* t-stat and reprogrammed the fans to come on at 190* instead of the stock temp (220??). Now there is no loss of power after warming up.

 

Knock retard most likely.
Put 92 octane in it or 100 unlead race gas and see if it's real knock.
If it's false knock ya need the proper resistor inline with the knock sending unit,or have it programed out.
Ya can find it with a board search and ya can get it at Radio Shack.

 

i will try that. thanks

 

I would attribute it to a lack of throttle response due to high IAT's. Every car I have ever owned lacks a little TR when it's fully warmed up, just as on a cold winter day the car feels like it picked up 30 HP. Even with a 160 stat and programming I can feel a loss in tip-in response and low-end torque below ~2000 RPM when the engine is fully warm. It's perfectly normal.

 

My 1994 Car Does That Same Thing, I Cant Seem To Figure It Out Either, But I Do Notice A Little Drop In Fuel Pressure When Its Warm, Maybe Its Time For A New Pump For Me.

 

If all the normal stuff (plugs, wires, fuel octane, air cleaner, etc.) seem to be in order, the next thing would be to get some cheap or free datalogging software, plug in the 'ol laptop and see what's going on. Look for knock retard, rich or lean reading from the o2's, etc.

Mine was behaving similarly and it was because I removed the air silencer on the intake elbow and made my own 1LE insert, which was leaking. Vacuum leak between the MAF and TB made the 'puter think it was running lean so it added fuel and pulled timing. Put the silencer back on - problem solved.

 

i put the resistor on the knock sensor. i always put 93 gas in it and i know that it is not knocking. i have datamaster and it was pulling like 9-13* of timming out when it warmed up. now it runs GOOD. i also have a 160 thermostat but need tuner cat to make my fan come on earlier. also is the TB bypass really do anything? also thanks for the all the input guys.
nick

 

This is a bigger more noticable problem then that Izzy. The engine will even backfire if accelerator is kept in a certain position as to keep the engine within the idle to 2000rpm area. OR if you feathered the accelerator, the repeatitive stalling of the engine will eventually cause a backfire through the exhaust manifold. I am having the same problem.

Here is a vid clip of the problem. Watch and listen carefully..
http://www.geocities.com/madd_Z28/MOV02475.MPG file is 223kb.