Tracking down a misfire

Hi
Took my 2001, 4.6 P38 (94K) into local stealers as I have a problem shifting through the gears. They indicated there was a misfire - and wanted £370 pounds to replace the HT leads before they could go any further. I thanked them (!) and purchased a leit set of HT cables and a MAF sensor.
Fitted both on Sat - car is now much much better, changing through gears better....but there is a definite low grade misfire.

Wondered if I could have not put the HT cables on quite right - they are a pain in the butt....

It has new plugs too...

Can any one advise how I might track down which cylinder the misfire is on - is there a tool to read an error code ???

Im guessing it may be the coil pack - how diffiocult is it to change... ?

Any (positive !) advice appreciated

Gaz

start it in the dark and look for blue flashers thats the easy way ..

Various methods.

1. Start it up from cold for a 10 secs or so, shutdown, then check the temperature of the exhaust headers for each cylinder - a cold (or much colder than the others) one would indicate that cylinder is not playing ball.

2. unplug/replug one injector at a time and start her up, obviously the car will run rougher, but the erratic nature of the problem should disappear when you've found the suspect cylinder.

3. Do a (wet/dry) compression test if you have the tools or know someone who does.

Get the codes read after checking in the dark,otherwise u will start replacing parts blindly.it could be simple as a plug replacement lead or coil.and worse as a cracked block leting coolant in in the cylinder

On my previous '88 RRC (I know we are discussing P38 - same principle though) when I changed the HT Leads, I had them in the right orientation (Right lead going to Right Plug) but I had crossed a couple of leads when routing them, this had the effect of cross firing the plugs...(one would fire when it wasn't supposed to).

The engine ran with a little hiccup/misfire but only slight, and what it was, was the crossed HT leads. it had the effect of firing two plugs at once due to induction currents, and this leakage would reduce the current getting to the correct plug causing a weak spark, and also firing the crossed lead plug to fire out of sequence....

Might be nothing, but wouldn't hurt to check you plug leads..!!

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