My friend got a 1994 xj with a rebuilt 4.0 HO about 13-14k miles ago.

Never had CEL come on. It starts up until it get to temp then when idling, it ll be rough, sometimes missing. Sometimes stalling. And when giving it gas to keep idle up, it would just fall flat on the face.u can even hear it pop thru the intake.

He replaced all the cap, rotor, wires, plugs, pressure regulator, cleaned the throttle body real good, he also replaced the throttle position sensor and o2 sensors.

Still getting strong exhaust fumes.

When it's moving, it's running great, but when stop at lights or intersections and idle, that's when the problems come up.

His wife has cancer and he can't afford to have the jeep break down while on the road.


Do u have any suggestions?
Thanks!

 

IAC? MAP? If it's not idling the IAC would be my first try.

 

He said he ll check the IAT and he also said the map is clean. Any other thoughts?

 

He just replaced the ignition coil. It was cracked in four places, it run much better now but he rough idle is still there. Any ideas what else could be causing this?

 

you could get the exhaust pressure checked to see if there is a restriction somewhere, like in the cat. Maybe it's not totally clogged and that's why when the rpm's are up it's pushing it through, but at idle it's pushing back.

 

Thanks! I ll pass that along to him

 

Bump

 

He checked and torqued the intake manifold bolts and it improved more, but still something amiss. U have any more ideas?

 

How are the brakes? Does it feel like the vacuum booster is working?

 

Brakes r perfect and when he's driving. All is perfect, but the problem only happen during when he's idling at red lights or parking.

Ignition coil replaced, improved a lot
Re torqued intake bolts, improved more

He says it feel like there's so little something short of perfect running engine

 

I'm putting my money on the EGR system. My stepmom's van had a horrible idle at stoplights if she left it in drive. It would even die sometimes.



When the engine is cool, press on the intake side of the valve and see if you can move the valve in and out. If it doesn't move, then replace it or delete it. Most people just delete it because they can still pass emissions without it. Really, it's obsolete and is just there to go wrong and cause headaches IMO

EDIT: I got this mixed up with another thread, your 94 doesn't have an EGR

 

He says his model doesn't have that

 

Yep, see my edit

 

Lol sorry. I didn't see the edit before I replied

 

A strong exhaust smell tells me a cracked manifold which happens to every 4.0 anyways.