87 XJ Idles rough after replacing clogged injector

[aemilehi]

Hi All,

I have an 87 XJ 4.0L fuel injected. Was running and idling fine until...

Noticed a significant gas leak from an injector on Saturday. Replaced all the O rings and still had a leak from the top of the injector, so 86 bucks and an hour later, the injector is replaced. Now, the idle is really rough, feels like it's missing a bit, and puffs of black are now coming out of the exhaust. It's also idling at lower RPM than usual, though it feels peppier and smooths out when running around the block now that the new injector is in.

The black smoke never happened before the install. I wonder maybe a fouled plug (though not sure why that would happen since they are on the opposite side of the engine) and I plan to change the plugs today, but it really seems like it needs to be timed and my manual says you don't time the 87.

All advice welcome and needed.

Alex

 

[MudderChuck]

I´d take a real close look at the vacume lines, the extra air will cause the 02 sensor to dump extra fuel into the motor, causeing it to run rich (black eyhaust). One tip off, is when you start the motor it idles up pretty high, then settles in to a lope and poor idle.
Maybe your new O rings didn´t seal correctly, or one slipped. I usually coat them with vaseline when trying to slide them in, makes life much easier. Spraying a light oil around each injector, with the motor running, sometimes changes the pitch of the idle. Some people use a unlite propane torch, blowing propane around the injector, some use spray grease (my technique/works but makes a mess). I really hesitate to use flamables around a running motor.

 

[aemilehi]

Thanks MudderChuck!! Your assessment was right on...the line from the MAP to the throttle body was so old it was brittle and apparently a slight bump during o ring install made it crack. Got the part at the dealer, installed in about 30 seconds and she's running like a top! In fact, even better than before!

Alex

 

[XJNick]

Hi,

Yeah, you've got to be careful with that line. It can break, or you can be dumb like me and accendentally plug in in to the wrong port on the throttle body. Mine has the correct port, but then a dummy port above it which goes nowhere (it terminates in the rubber block there) :roll:

-Nick :!:

 

[MudderChuck]

I´ve done the same thing, when replaceing intake/exhaust gaskets, broken, cracked or split one of the little hard plastic lines. Really messes with your idle.
Got my Jeep back from a smog test, with the stopper, XJ Nick was talking about, unplugged and laying on the manifold. I´m gonna take another look, thanx for the heads up Nick.

 

[badcj5er]

HI, IF YOU INTERESTED, I HAVE A ARTICLE ON THE SENSORS & HOW THEY WORK, & HOW TO CHECK THEM. YOU'LL HAVE EMAIL ME YOUR EMAIL ADDRESS AS THEY ARE IN MY FILES, & I'M NOT ABLE TO SEND THEM THRU THE FORUM. BADCJ5ER EMAIL--jeepman600@aol.com