2000 XK8 Misfire.
 

Hello All!

So i have been working on Emerald trying to fix My rough running. To start with the first time i checked codes i had:

P0171 bank 1 to lean
P0174 bank 2 to lean
P0300 random misfire
P0304 misfire on #4
P0354 coil circuit fault
P 1316 injector circuit
P0305 misfire on #5
P0706 transmission range sensor.
Looking through the threads i found a member who had a misfire problem and had codes 171, 304, 354, and 1316. his problem ended up being a bad coil.
so for the fun of it i bought two plugs and two coils and put them #4 and #5. I discovered at that time that the plug tubes were full of water. {the coil covers are
missing} i cleared the codes and fired her up. this time i got:

ABS light ASC/TRAC not available
and misfire codes for 2, 3, 4, 6, 7, and 8
and of course still rough running.

thinking that was an odd change i cleared the codes and fired her back up. this time rough running but no codes 0! no lights either or reduced power message.
so i did a hard rest and tried again. this time i got codes:

P0171, P0174, P0300, P0302, P0304, P1316 and P1000.

Any ideas? the p1000 is kind of obvious. I'm thinking the P0304 and P1316 may be indicating an injector fault, Also thinking maybe i had both an injector and coil problem
as before i had the P0354 which is now gone since i replaced the coil. P0174 a vacuum leak or air intake tube leak since there are no misfires on that bank now.....
this train of thought sound reasonable, or am i missing something?

First point of call is BATTERY CHECK.
Vehicle details may also help in members diagnosing your problems as there were changes to systems throughout the X100 production.

After the battery check, you may want to look at threads etc related to the ECU capacitor issues and replacement of the caps, as these can throw random codes and poor running.

Before deciding it must be a mysterious module playing up and sending it off for a rebuild, check the live data with your scanner and see what the fuel trims say. You are running lean on both banks, so you either have a huge air leak, or your fuel supply is restricted (filter, pump, old fuel, check fuel pressure etc). You should also clean your MAF and see what readings you are getting from it in the scanner to see if it makes sense.

These are all basic tests really before doing anything else.

Baxtor, very first thing i did was put a new fully charged battery in it. as for details i tried to save the car to my profile but that didn't seem
to work. so that's why i titled the thread " 2000 XK8 misfire" so at least the year and model would be out there........

Shiner, i'll probably look at those just for the hell of it. who knows it might be the issue.

Dibbit, i won't be sending the ecm off for a rebuild until I'm sure that the problem. i don't work that way, i like to find the problem 100% and fix it
as for the trims, i don't remember exactly what the readings were but it seems like them and the m.a.f. readings all pointed towards lean running.
i got this car with it already having issues, the P.o. was convinced it was in the fuel system. He has passed so i can't ask him what he had done.
it was stored when i picked it up, but with no fuel in it. so, no old gas. i have a new filter but have not changed it yet. i need to check the pressure.
it does act at times like it's starving for fuel so it may very well be there. sometimes i swear i hear a vacuum leak, but then the next time i start it
i don't. So that maybe an intermittent problem too.

I suspect the P0171/4 & P1316 are a result of the P030x so I'd next be trying known good coils / moving them around.

I'd also watch the idle fuel trims but bear in mind misfires look like lean just because there's unused O2 due to an incomplete burn and so there doesn't have to be an air/vac leak (i.e. doesn't rule leak in or out).

That's a good point - is the misfire caused by being lean, or is the misfire causing the lean condition? The lean condition being reported is on both banks, and the cylinders showing misfires on his last set of DTCs are on the same bank, so I would have thought fuel rather than spark, but who knows.

Definitely worth swapping the coils over to see what happens as it is a relatively easy test to do, followed by replacing the fuel filter.

If you have no evidence the fuel filter has ever been changed (I.e. original), then it most definitely needs to be changed. Check your fuel pressure at the rail(s).

Brian W.

Definitely check the fuel pressure. Fuel pumps tend to go bad if they sit very long, especially 25 year-old ones. The accordion tube (intake pipe) is also a common issue with lean conditions - cracks in the plastic from years of heating and cooling. The ECMs are known to fail on the MY 2000s. There may be a VIN range, Motorcarman probably knows what it is.

JagV8 remember i REPLACED the coils and plugs on 4 & 5. misfire on 5 gone still have misfire on 4. although the coil circuit fault on 4 is gone.
still have the lean condition codes misfire on 2 is a first. so, I'm thinking the misfire is because it's lean. I'm going to smoke it this weekend and see
what i find.

Dibbit, my plan is to change the fuel filter regardless of it's condition. that's due to the fact that some very questionable things have been done to this poor girl. my plan is too check
the fuel pressure before and after changing the filter to see if it was a restriction. if i have no leaks with the smoke and fuel pressure is good, then i have a couple more new coils i'll
swap in.

for the misfire - check the cable harness going to the coil packs. The insulation on my wire bundle was flaking off, so had to wrap each wire with electrical tape until I can get a replacement cable harness

It's free to move coils around a bit more just in case it's diagnosing the wrong cyl faulty. Wiring is worth examining for sure.

Tis True sir!

fuel pressure is good. so that's not the cause of the lean condition. smoke test to come.

What if I'm actually looking in the wrong place? what if it's actually a wiring problem? once again, the ABS light ASC and TRAC not available randomly popped up again. along
with a low brake fluid warning. but i know for a fact that the brake fluid is full and has been. and the other three warnings come and go randomly.

Could be. Chafed harness, moving around a little.

Even a relay with dirty contact(s).

i have read in a couple threads that the ABS Module's known problem can cause the "reduced power" message and rough running. can anyone elaborate on that
for me? I'm curious if the random ABS/ASC/TRAC warnings could be the known Module issue and that in turn affecting the ECM........