I have a 97 discovery xd, 4.0.

I was installing a new stereo headunit and left the ignition on during an extended break. Now I have the headunit in (it sounds good, anyway) but the battery was dead. Tried jumpstarting it with a protable unit - no good, the unit wasn't charged enough - so I put it on a charger. The engine turns over, even starts, but runs extremely rough, lots of backfiring and such.

I have an OBD code reader but it doesn't always return a code. I got no faults when I started trying. Pulled all of the plugs anyway. All are covered with black soot. Tried starting after cleaning all and it started easier but still rough. Code reader came back 0300 and 1316.

Thought it might be the battery since I completely discharged it. (Old anyway) installed a brand new battery, no change.

So the two big changes are the new stereo (which I have pulled back out - no change) and the dead battery. There is a distinct possibility that I may have caused a short or two when wiring the new radio. There is a possibility that I shorted something when I tried jumping the dead battery. When the car is running I am getting 13.5 volts at the battery terminals, so I don't think it is the alternator. No fuses blown. All plug wires tight.

What else could I have shorted out? Is it easy to short out the coils? What about the engine computer?

Where do I start in diagnosing this?

Any help appreciated.

The good news: It is highly likely that you do have a fault caused by the dead or disconnected battery. You are not getting an SRS light? This is a pretty common D1 issue.

A reflash from Autologic is probably the best place to start although it is worth waiting to hear from others who may know how to otherwise get around that. New battery will not clear the system if this is indeed the problem.

The bad news: the battery issue may have precipitated the system finally throwing codes on carbon build-up / fouling. I don't know what the codes - 0300 and 1316 - refer to, but if they are specific cylinder misfire codes, sticky exhaust valves may well be the culprit rather than an ignition issue. As I understand it, the early GEMS chips in the 4.0 contributed to the problem and inhibited diagnosis - but there are others more knowledgable on the subject than I who may be able to shed more light on it.

Before worrying about a valve job and taking heads off, check out whether the dead battery is causing you to throw codes and what those codes you were getting mean.

Thanks for the advise...I am not familiar with Autologic. Is this something I can remove the ECM and take into a shop to have done? In its current state, the car is not roadworthy and I hate the thougt of towing it into town - we are fairly remote where we live.

got it to start - still running rough, but it will idle.

It ran long enough to finally give me a fault code - p1314

Curiously though, I do not have any warning lights - SRS, CEL, SEL - nothing. Is this another clue towards the ECM being a problem?

If you killed the battery by overcharging, have a weak cell or other battery issue you will have missfire issues as well as the ECU may "lock up".

I have had to toss several batteries that have been drained and overcharged leading to running issues (generally high idle and missfire). Need to reset operating parameters and install a new battery.

This is not grandmas car, and is somewhat sensitive to voltage issues. Even a loose battery wire will make it run all fawked up.

So how do I go about "resetting the parameters"?

Final update-went out early this morning to start her up to look for sparks in the dark and it started right up and ran like a top. Drove it for about 15 miles with no incident, no codes.

The evil spirit of Lucas, Lord of Darkness still roams.

you need to clear the adaptions or reset adaptions for the ecm
and it should run smoother

Resetting adaptive values should help, but will not correct the misfires if they are due to either a clogged injector, poor secondary condition, or fouled valves.

Actually, the truck has been running fine. My theory is that I got fuel down in the cats while trying to crank this thing and once it dried out, back to great. That or I sooted up the O2 sensord - the plugs were covered in soot when I pulled them - and running some carb cleaner down the bore helped with that.

Anyway - all this talk about the values of resetting my ECM but so far no one has answered my question about how to do that.

So - how do you do it? Are there risks involved? Is it something that should be done on a regular basis?

Anyway - all this talk about the values of resetting my ECM but so far no one has answered my question about how to do that.

So - how do you do it? Are there risks involved? Is it something that should be done on a regular basis?

The OBD-II rigs have the ability to trim engine operating parameters to match the driving habits, fuel, atmosphere, etc to optimize engine performance.

These adaptive values as they are called can be reset to factory default settings using a Rover-specific diagnostic tool.

Risks? No. Regular basis? No. The engine is constantly learning how and where you drive and what sort of fuel you use. Under regular conditions, it is never necessary to reset these values.