Idle varies/rough

[67bbc]

Having problem with the idle, will not stay steady. Idles up/down between 850-1100. 1991 YJ, fuel injection, 2.5l 4cyl. with about 120k miles. Changed the plugs, wires, cap, rotor, TPS, etc. I took it took one shop and they could not figure it out. Any ideas (engine/valves, fuel)???

:-? [addsig]

	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).

[Bounty__Hunter]

Clean the throttle body, along with the Idle Control Motor, should be on the throttle body. Is the '91 TBI or MPFI? I'm thinking that's the year they switched to MPFI. If it is, the IAC motor is on the passenger side of the throttle body and controls the idle.[addsig]

[JE420EP]

When was the last time you changed the fuel filter. I bad fuel filter will make it run like crap too.[addsig]

[67bbc]

I changed the fuel filter, idle control valve, nothing better. It is the MPFI. I will try cleaning also and see if it helps. Thanks for the advice and if you can think of anything further let me know.[addsig]

[[]lllllll[]]

I'm not sure i can help you out on this one, but i have the exact same problem on my 91 2.5. it will idle any where from 600-1250 rpm. My engine is rebuilt, i have replaced the o2 and tps sensors, new fuel filter and cleaned out my idle control and have a new air filter and straight pipe. SO... can anyone tell me what i haven't replaced that i need to replace? i've put injector cleaner in there about 3 times, and i have a new cap, wires and new platnum plugs. Timing is perfect. throttle body is spotlessly clean. but everytime it rains or i go thought deep water it will f#@k up and run really crappy. can anyone help?[addsig]

	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).

[jay89]

I would alos check all you vac hoses for leaks?[addsig]