b_heier.4X4

So I'm changing my CPS this weekend cause I've had speratic starting problems lately. But on to my question, should I also change my TPS and IAC as well? it seems to run a little rough???it has strange RPMs while driving(just kind of does whatever it wants) and just Idols a little rough in park...I also just gave it a tune up(spark plugs, wires, cap and rotor)it's a 1996 sport and has 87330 miles and needs new O2 sensors if it matters. so should changing my CPS fix all of my problems or should I just change the rest of the sensors to be sure???

Spoonman

I would go through and try to diagnose the cause of the problem rather than just randomly replace parts.
Have you checked your fuel pressure?
You said plugs,wires,cap and rotor but what about your air and fuel filters and other miscellaneous tune up items that often are over looked?

Also what makes you think that you need new O2 sensors? If you are getting a code for that it does not necessarily mean the O2 sensors are bad, If you jeep is not running right it will trigger the codes for the O2 sensor(s) because the exhaust is rich/lean or what ever the condition happens to be. Try to find your idle issues and fix them before replacing the O2 sensor.

Another edit lol, what did the old plugs look like? color and were there any heavy deposits on them etc etc

b_heier.4X4

The reason It needs new O2 sensors are that I just bought it and I'm pretty sure they are the original O2 sensors and I'm getting crappy millage11-12...and it's all stock! The air filter is nice a clean. The old plugs were beyond terrible!!!! They were a lame excuse of a spark plug...all coroded looking and the gap was like .063 twice what it should be.

Spoonman

So no codes then.Thats good. I would still diagnose the problem before just replacing a bunch of sensors.
The O2 sensor is $50-$60 so lol that's good enough for me personally to try and find some cheaper issues before jumping into the higher dollar items.

Sounds like none of the old plugs were gunked up or wet then so that is good news.

What about your fuel filter and fuel pressure?

If I had to pick a sensor just to replace hoping it would fix an erratic idle then I would start with the throttle position sensor.Of course thats around $60 too but lol gotta start somewhere I guess.Seems like everything is at least $50 these days.

Defiantly make sure you have a clean fuel filter and are getting proper fuel pressure first though.

NCMetalMechanic

ok, so i know that parts store like to try and sell o2 sensors by saying things like "do you want better gas mileage?" in their ads (that a certain company with a "Z" in their name ran all summer and fall on the radio) but o2 sensors are NOT a maintenance item. replacing old ones that aren't busted will NOT magically give you better gas mileage, and make your car run better. I completely agree with Spoonman, figure out what the problem is before you start throwing parts at it. you'll be happier, and more importantly, your wallet will be happier.

I know it may sucks, and nobody wants to have to pay to have a problem diagnosed, but it may be worth it to take it to a shop and let someone else deal with the headache of chasing your problem, i can almost guarantee the diag. will be cheaper than throwing parts at it

b_heier.4X4

Thanks for the help guys
I'm going to look it all over again this weekend and make sure before I start throwing parts at.

tjwalker

Oxygen sensors have a finite lifespan of between 100k - 150k, depending on the efficiency of the engine. They can become "lazy" before they set a code.

Replacing the crank sensor is not likely to fix the idle symptoms.

Testing your throttle position sensor would make sense before replacing it.

If this were mine, next thing I would do is to thoroughly clean the idle air control and throttle body. More on this.
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The Idle Air Control (IAC) is mounted on the back of the throttle body. The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)

“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged

Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.

Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner

It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled

Reinstall IAC and check idle quality

freegdr

just becasue there no check engine lght doe not mean there is not a problem codes should be read and replace one thing at atime this avoid having new problems and not knowing what caused them replace something start and run repeat