98 Wrangler 4.0

jeep
wrangler

#1

Anybody know what the black box under the hood on driver side, just above front tire does? It has 2 small vacuum lines and one large (large is at the top of box) The large nipple appears to have had a hose on it (going where i dont know) Im curious if i should plug it.???

Note. Cruise control worked when i bought it but hasnt worked since. This box have anything to do with cruise control?

Thanks


#2

Also. Cats have been removed. Check engine light comes on with p0420 (Catalyst efficiency below normal (bank 1)

I added spark plug defowler to O2 sensor, light stays off longer but still eventually comes on (about 10 days)

It has new exhaust manifold, Is there a trick to keeping the light from coming on? or is there maybe a real problem?


#3

If the CATs have been removed, of course efficiency is below normal. That is what O2 sensors do. They measure exhaust gasses and the computer adjusts the air fuel mixture to increase efficiency and decrease pollution.


#4
Is there a trick to keeping the light from coming on? or is there maybe a real problem?

Yes, there is a trick. Put the Cats back on. And yes there is a real problem, There are NO cats.


#5

The problem as I see it is that you’re trying to treat symptoms instead of the cuse(s) of the problem(s). You’re trying to make the light stay off instead of fixing what made it come on in the first place. You either need new catalytic converters or you need to reinstall both oxygen sensors properly, without spark plug defowlers. Then, after you’ve got good cats and good sensors, if you still get a code, you need to diagnose the cause of the code and fix what is wrong.

I know Chilton, Haynes, and the other repair manual publishers have gone downhill, but if you need help identifying components under the hood, that is still one of the few things those books are good for. I tried searching online for engine diagrams for this model, but they don’t seem to include that component. As a last resort, take a picture of it, take the picture to the parts store, and ask the guy behind the counter if he can identify the part.


#6

knfenimore

I know what the cats and o2 sensor do, but thanks

That will be a spendy fix. Was trying to get around a whole new exhaust system


#7

How ya go


#8

That looks like an air box/cold air intake to me. EDITED: Maybe it’s the OEM/stock air filter housing and it was disconnected when a previous owner modified the air intake or replaced the engine.


#9

Thanks. I will study that


#10

Sorry. You never know who your talking to or the level of their knowledge.


#11

No Problem


#12

It’s the evap system carbon canister:


#13

hmmmm “spendy fix” that s a laughy comment


#14

@badbearing‌

Cats have been removed. Check engine light comes on with p0420
(Catalyst efficiency below normal (bank 1)
I added spark plug defowler to O2 sensor, light stays off longer but
still eventually comes on (about 10 days)

I agree with others that you’re on your own here.
But if you want the p0420 light to stay off, then unscrew your rear O2 sensor from your plug-non-fouler, stuff some steel wool into the plug-non-fouler, and reinsert the O2 sensor.


#15

Good call @insightful . Yes, it does appear to be the charcoal canister. One connection is probably to the top of the gas tank (to collect the fumes from the gas tank so they go inside the cannister), the second, through various valves, eventually goes to the intake of the engine (to burn the excess fumes stored in the cannister) , and the big one with the yellow thing probably vents via a filter to the atmosphere to allow air to slowly enter the canister (to prevent excess vacuum from building up).


#16

Thanks Guys

Wesw. What you laughin about?


#17

ahh. I guess i best remove my homemade cap and let it vent

The steel wool with the o2 sensor i have to question, I had 2 non-foulers on there and it didnt run right. Removed one and now it runs right.


#18

just your wording was humory. :slight_smile:


#19

Get an 02 sensor simulator. here is one, but there are others and i think there’s even a UTube on how to make your own.

http://www.ubertechnics.com/O2_Simulator_2.5.aspx


#20

The steel wool with the o2 sensor i have to question, I had 2 non-foulers on there
and it didnt run right. Removed one and now it runs right.

@badbearing‌:
I’m assuming you’re only talking about the rear downstream O2 sensor.

I’ve not seen any evidence of the downstream rear O2 sensor being used for fuel trim (engine operation). I’ve only seen diagnostics as it’s role in life. If someone knows of manufacturers using it for fuel trim, please share.

The steel wool serves to enhance what the non-foulers are doing, which is to further “deaden” the air at the tip of the O2 sensor.

Using non-foulers in upstream sensors will affect fuel trim. You don’t want to do that.