slimjimvinny

The rig: 97 Sport 5 speed 229k

The problem: stumbles when cold. If i blip the throttle it'll start to die for. Sec before revving up. Once warmed up, problem goes away.

The info: all stock everything. Anmeter on dash shows 14v running, battery is way old and should have bEen replaced years ago. Im thinking battery or intake leak?
Thanks

salad

Possibly, generally vacuum leaks show up ad a high idle. You might check your TPS and IAC for proper function, as well as check the fuel pressure. When was the last tuneup?

Bustedback

Sounds like a sluggish IAC motor.

slimjimvinny

So according to Carquest my battery is only putting out about 350 cca, but my alternator is all good. So, I know I need a new battery (but I knew that already).
To answer: last tune up has been QUITE a while. Due to financial issues the Jeep has been a bit neglected while still pulling DD duty. Luckily the climate here is mild!
Embarrassingly, whats a TPS and IAC? Im gonna head to a shop for the new battery and a tune up in the next few weeks (a$ $oon a$ it'$ po$$ible) and I'd like to steer them in the right direction.
Thanks for the help!

salad

The Throttle Position Sensor and Idle Air Controller are in the throttle body. The PCM uses the signal from the TPS to figure out how much fuel to dump in and tell the transmission to shift. It's also used to determine when the throttle plate is shut so that the IAC will open up to let enough air into the engine to maintain an appropriate idle speed.

A good place to start would be carefully disassembling the throttle body and cleaning all components with throttle body cleaner and a soft toothbrush. This will take care of the TB itself, throttle plate, Manifold Absolute Pressure sensor (left side unit, also sets air/fuel map), TPS (rear unit), and the IAC assembly (right side). The gaskets are reusable if you're careful and don't damage them. Note when cleaning the IAC that the plunger that comes out of the motor is quite sensitive - don't push on it or anything.

tjwalker

1. Get that new battery installed and also perform a tuneup. The importance of fresh tuneup parts cannot be overstated! Fresh Champion copper plugs gapped to .035, quality plug wires, distributor cap and rotor with brass contacts.

2. Clean your throttle body and idle air control. Procedure below. Good luck!
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The Idle Air Control (IAC) is mounted on the back of the throttle body. (front for 87-90) 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