NewKindOfClown

Yep. It releases fumes from your gas tank into the manifold to be burned. It's for emissions.

1999SilverJeep

Hey y'all. Question: Did I damage my engine?

So I was driving in the woods and my radiator burst. Seemed like some kind of relief valve as the smoke was pouring out of the right side of the grill near where the radiator hose meets the unit.

I don't have AAA so I drove it home stopping every 2 miles to refill the coolant manually and let the engine cool off. It was cold, windy, rainy all of a sudden. That happens in New Mexico. Made it home 6 miles. At one point the engine temp got up to about 240 or 260 so I quickly pulled over filled up the coolant and turned the engine back on to circulate the coolant. The temp gauge quckly dropped back to about 210.

Still starts up. Sounds a little wonky. I'm gonna have a mechanic do the work for this one. Think I damaged my engine??

odgreen

Head might be warped.

Eagle564

Ah thank you.

Which O2 Sensor affects gas mileage the most if it were to be bad? Or are both of them equally responsible? $60 some a piece so I'd rather get away with just one if that could be a good improvement. The only way I can be getting this bad of mpg is sensors. Dang near everything is spotless other than the coolant and oil leaks. I really don't see how it could be anything other than bad sensors, whether that be O2s or some other ones.

straightsixjeep

The upstream is what reads the o2 which the computer see's to determine the a/f fuel adjustment. The downstream is mostly there to make sure the catalytic converter is running efficiently. It also does act as an upstream o2, however the upstream does most of the work. I believe the upstream o2 going bad would cause the biggest mpg decrease, however I have had a downstream o2 go bad which caused the same thing.

Eagle564

Dang, well I suppose I'll start with the upstream. How about a bad fuel filter? I would think that would have the biggest impact.

Cherokeekid4x4

Or IAC. I have to test them to figure out which one is the problem. Edit: someone answered the tps question, what about the IAC? Will that cause lower mpg?

straightsixjeep

Here's a neat thread - https://www.cherokeeforum.com/f2/top...ileage-157522/

I would imagine a plugged fuel filter would cause bad mpg since its starving the system of fuel causing it to run rough. However several posts down Cruiser says it wouldnt cause bad mpg. Is your fuel filter inline? I know the 97'+ are in the tank.

Cherokeekid4x4

Fuel filter doesn't affect it much. Swap it anyways. Good routine maintnence and cheap and easy.

cruiser54

Nope.

O2 sensor, yes.

straightsixjeep

The biggest thing it effects is idle when it gets carbon'd up. It can cause a rough idle and it can also cause your jeep to idle excessively high upon start up. It wouldnt hurt to get a can of throttle body cleaner, not carb cleaner, and clean it.

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

Cherokeekid4x4

Dang. That means I have a bad tps or iac and bad mpg. Just out in a new o2 sensor. Also a fuel filter. Mpg is a tad better but there's something else causing bad mpg. Hmmm...

connolcj

Does someone know what vehicles and their years for longer brakelines? I want some that will work for about 6.5" of lift. I want to go and buy new ones from the parts store in the next day or two.

straightsixjeep

Have you done a full tune-up on it? Whats your tire pressure?

Cherokeekid4x4

Thanks man