[jfrabat]

Well, I guess I have something acting up; if I install the 2.5L TB, the engine runs OK until about 4,000 RPM's, where it starts to stutter and will not go past it. With the 4.0L TB on, the idle is acting up, and the engine will not rev up propperly (I get a lot of smoke from the exhaust, some backfiring on acceleration, and stalling when flooring the gas pedal).

Keep in mind that neither the TPS or the IAS are the problem, as I replaced them thinking it was them that were acting up. I also replaced the O2 sensonr about a month ago. As I mentioned, I know my fuel system is not up to par, but in your opinon, is this the problem, or is my problem somewhere else? Opinions extremely welcome at this time...

For the time being, I have uninstalled the 4.0L throttle body, as at least with the 2.5L TB I can run the Jeep to work and back (even if I cannot accelerate to 4,000 RPM's, regardless if I am in gear or just revving up the engine on neutral).

Felipe

	Throttle position sensor A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located on the butterfly spindle so that it can directly monitor the position of the butterfly throttle valve. The sensor is usually a potentiometer and therefore provides a variable resistance dependent upon the position of the butterfly valve (and hence throttle position). The sensor signal is used by the Engine Control Unit (ECU) as an input to its control system. The ignition timing and fuel injection timing (and potentially other parameters) are altered depending upon the position of the throttle, and also depending on the rate of change of that position. For example, in fuel injected engines, in order to avoid stalling, extra fuel may be injected if the throttle is opened rapidly (mimicking the accelerator pump of carburetor systems).