My 2001 XJ has started stalling for no apparent reason after I did the following

-Air filter
-Oil change
-E2 spark plugs
-Coil pack

I'll think it has only stalled while coasting and while at a stop. I can't recall it stalling with my accelerator pedal depressed.

It won't stumble or anything it just shuts off as if I turned the car off. I'll put in it park and turn the key and it will start up again without any problem.

It has happened when warm and cold. It doesn't throw any codes.

I've looked for loose connections which I can't find any. I've also put the old coil pack back in to elimintate the posibility of a faulty new coil pack. It stalls with both the new one as well as the old one.

This is driving me insane. I can't figure it out. Any insight would be greatly appreciated.

 

I would clean the IAC. Also, not familiar with E2 plugs, but XJs generally like Champion or NGK.

 

Mine did this too. Clean inside the throttle body and check Your tps sensor or whatever its called

 

This is a hallmark of the IAC not letting in enough air when the throttle plate is shut (foot off pedal). This could either be the IAC itself or the TPS sending a bad signal.

The IAC is a little stepper motor that operates a plunger beside the throttle. You can see it mounted to the side of the throttle body closest to the actual engine. IIRC it's held on by a couple of torx screws. Gently take it off (you can reuse the gasket if it's not damaged) and carefully clean out the guts with some throttle body cleaner and a tooth brush. The motor inside is delicate so don't force the plunger around. Even if it's not the problem, this is probably full of black sticky crud.

The TPS is installed on the rear of the throttle body, opposite where the arm that has all the cables connects. Pop this off and give it a similar cleaning.

While you're doing all of this, it's actually a good idea to remove the entire throttle body and clean everything. It's best to do this while it's off of the intake manifold so you don't blast all that crap into the engine. You'll also get the opportunity to clean the MAP (mounted on the driver's side, nearest the brake master cylinder and air cleaner)

If cleaning the parts doesn't sort it out, you'll need to test the TPS. With the key set to RUN (so the ECU is powered on but the engine hasn't been started) back-probe the wires going into the TPS with an analog multimeter. When the throttle is closed, you should see a +5V DC signal going into the unit on one wire, a ground, and a 'signal' wire that should show near 0V. As you open the throttle the TPS signal wire should move steadily and smoothly up to +4.5V DC. If it doesn't, the TPS is shot. If all this checks out then it's likely that the IAC has gone **** up but that's not as common as the TPS.

 

Don't forget the battery; it is a very common cause of stalling (at idle).

Any parts store will "load test" your battery for you for free. Load testing is the only accurate way of testing the condition of your battery......
And yes, you can have a battery that is strong enough to start the engine, but marginal enough to give the engine management system fits and create stalling.

I don't think the spark plugs would be a cause of this stalling, but in general, I'd stay away from specialty plugs and stick with NGK coppers for your 2001 4.0. Some have had issues with specialty plugs that have been directly traced to those plugs.

Good luck and keep us updated!

 

^^ I had the same problem and replaced the battery and it took care of my problem. Hope that is as simple as that for you too.
BTW, Those E2 plugs are garbage. I would pull them and replace them with NGK for you year. NGK are recommended for 1999-2001 and Champion for anything older.

 

Thanks guys,

At first i didn't think it was the IAC or TPS because it didn't throw any codes. I'll take a look at them this weekend. I'll throw in some regular plugs too. We'll see what happens.

 

I forgot to update this thread. It turns out it was the expensive E3 plugs. I put a set of OE ones in and voila, problem solved. I'll be writing a letter to E3. These plugs were dangerous in my truck. On a few occasion I stalled right in the middle of an intersection while making a left turn with oncoming traffic coming right at me. I did more research and found out that I'm not the only one who's experienced this. Someone is going to get seriously hurt or killed with these things.

 

Thanks for the update. Yet another case of E3 plugs not working well with the 4.0 engine. Stay away from them folks......This is NOT the first case of issues with this plug in the 4.0. Search and you'll find plenty of others.