My 99 Cherokee start running rough after turning on the ac. Idling from 250 Rpms to 1500 Rpms with rich exhaust smell.

Now it came to the point that it run rough without ac being on. From 750 Rpms to 1,750 Rpms while idling in park. It sometimes hesitate while in drive gear.

The CEL came on today so I took the opportunity to check the code and p1494 came up. Says the Evap is leaking or something. I'm not even sure where or what that is.

I almost changed the TPS and IAC.

What do u guys think

 

If you Google P1494 you'll get a ton of ideas to narrow your search.

 

Yeah I did that and everybody pointed at everything, its still too broad. Ha. But thanks!

 

Do you have a Leak Detection Pump? Don't see them often in '99 XJ's unless they're Calforinia emissions compliant.

P1494-LEAK DETECTION PUMP SW OR MECHANICAL FAULT

Set Condition: The state of the switch does not change when the solenoid is energized.

Possible Causes:

WIRING HARNESS INTERMITTENT
LDP SWITCH SENSE CIRCUIT SHORTED TO GROUND
LDP VACUUM SUPPLY
LEAK DETECTION PUMP
LDP SWITCH SENSE CIRCUIT OPEN
POWERTRAIN CONTROL MODULE

 

I am from Pennsylvania and the jeep was made for East coast so I don't think it would have a leak detection pump.

 

I guess I will check all vacuum lines and the fuel cap tomorrow

 

I found that one vacuum line fell off the intake manifold because the elbow was rotten. I replaced that and put back on the nipple, the erratic idling stopped for 1 minute then it started again.

For a glorious minute I thought I solved the problem, I guess not.
After looking at other vacuum lines. I noticed that there's one line with green cap on it. It says Evap service port 1 psi max and it goes in a round thingy on firewall passenger side, and I can feel its clicking or something (remember I am deaf) so I don't know if that's good or not.

Is there any other places where vacuum hoses connect to in other parts of the jeep? I checked all connections on engine itself, I don't know where to check next.

 

Should I use vacuum gauge to check if there's a leak in Evap?

 

Anyone?

 

I happened to notice that under the jeep that a hard line comes out of gas tank and goes in a box then there's two tubing coming out and goes to the engine

What's that?

And I noticed that the rubber connector for the metal line into the box is dry rotten. Would that be causing the CEL?

 

That steel line coming from the top of the fuel tank is from the roll-over valve. It goes to the charcoal canister. Chit can the steel line and install a fuel rated rubber hose to the plastic tube from the tank to the charcoal canister, and use a coupler to connect to the replacement elbow on the canister.

There's a plastic tube that goes from the evap solenoid valve (green cap thingy that clicks when the motor is running) to the charcoal canister. Make sure that tubinig run doesn't have a hole in it and the rubber connector at the canister is serviceable.

There's a large plastic tube from the canister to the engine bay, and terminates behind the tranny fill tube. If you had a Leak Detection Pump it would connect to it. As it is, the large tube is useless going to the engine bay.

There's an emission decal on your firewal, on the driver's side, that has the evap schematic. Check it out.

 

Thanks. I went to parts store but they say its a dealer specific parts so I guess I ll be heading there tomorrow. (For those rubber connector parts thingy)