Spuddering when the key has been turned off.

My girlfriends 99 xj sport with sputter for 4 to 8 seconds after the key has been turned off. It doesnt matter for how long it has ran either whether it is 2 seconds or 2 hours. It is not running hot either. Could it be a bad injector that leaks and the preesure from the fuel line is causine it to leak? what could fix it. How do you check for codes on a 99.

thanks
skog

she took it to the shop this morning because it would start because the brand new battery that we put in on sunday night was only putting out about 8.5 volts and the starter would just click, not rollover. they said that the ignition cylinder always had power so they replaced the cylinder and the cylinder still has power when off. He told her that it is either a wiring prob or a computer prob. They were going to try the cpu first and if that didnt work find the short. does this sound right or do you think it is something else and he is jsut giveing her the run around?

skog

If the cylinder sends 12V out the RUN line even when in the OFF position, then either it's bad or you have a wiring problem. I don't think the PCM fits here.
Check connector C1 at the PCM (frontmost), pin 2 (second left to right on the bottom row). You should only have 12V there when the key is in Start or RUN position.
The wire is dark blue with white stripes.

Run on is a common problem if you have carbon buildup on the pistons or valves. It gets hot and glows hot. It causes the engine to diesel for a few seconds after removing the spark.

The carbon problem is normally caused that running too rich over an extended period of time.

The first thing to do is swap in a new set of plugs. Don't go with the expensive ones. Just get the $1 a plug Champions or Autolites. The expensive multi electrode platinum units don't work as well in a 4.0L. After changing the plugs, put a can of BG44k in the gas. It runs about $18 a can and is well worth it. Run a tank of gas through it. Then and only then start checking if it is still running too rich.

When you pull the plugs, they will be covered with deposits. One or more may be quite black with soot. Keep track of which plug went with each cylinder for future reference if you need to do more troubleshooting. Better yet, post a photo of the plugs when you pull them and from that I can give you a better idea of where your problem is comming from.

There is another possible problem, but it will show up when you pull the plugs. There is a possibility that she has a vacuum leak and has run so lean that it has a burned valve but that is unlikely. Either way the plugs and BG44K won't hurt and will help.

This is a long shot but check your battery cables and your ground wire to the engine. (like jldiaz said maybe a wireing problem) I know back in the day with my old ford 300 i6 it would mut and sputter for a good 30 seconds after i offed the key... one day i found the braided ground cable that went from the engine block to the frame was broken. so i took a piece of extension cord and hacked it up and ran it from fram to engine never had the problem again.

But that was a carb and it was an older style ignition... So i don't know if it applies to the 4.0l I have not taken mine off to try it...

The Automatic Shutdown Relay (ASD) shuts the injectors and the ignition off when no signal from the cylinder is received at the PCM. Maybe it's sticking.
(you'd need gas to diesel on, wouldn't you?)
The ASD Relay is in the POwer Distribution Center (PDC): The black box right behind the battery. There's a relay / fuse map inside the cover.

-- But it wouldn't sputter without carbon in the cylinder head, either......

She got her heep back this morning. There was 2 different shorts that were affecting the mention ASD. It is fix and she is very happy that all it was just a little wire chasing.

thanks
skog

Glad you solved it. Good luck!