2002 P035X When Headlights Turned On?!

[craaig]

So i'll try and keep it short (never works):

I'm getting code: P0351/P0352, but only when drawing load in the form of the headlamps/lights. Possible ground issue? or coil pack?

Context:

I left the parking lights on while shopping, upon returning to the car, it wouldn't start and the batteryappeared flat (isn't the first time).

Got a new battery and on it went.

Now it gets really ropey, misfires and dies entirely when the lights are turned on. I can run the car with no lights and it's lacking in power but manages.

The troublesome thing is, it's not always the case, sometimes the lights can be on and nothing happens, sometimes as soon as the lights go on, it instantly splutters and fails.

Any suggestions would be greatly appreciated?

Alt is giving me a constant 13.8V (F-Super reads 14.11V) with load, until that off a misfire then it goes down, but never beyond the battery's starting point of 12.6V.

For a while now i had a misfire between 50-60mph which almost but not quite cleared up when I cleaned the EGR valve.

[MONDEO TXS 2.2]

P0351 is indicative of a possible issue with coil pack #1 & P0352 is #2

[pragmatix]

What he said, more on codes here https://edgeproducts.com/app/uploads/2014/08/customer_support_article-pdf-41.pdf

[mgaking]

I would still start with the simple things first.

Given that it gets worse when the headlights are turned on I would make sure that all battery and earth connections are tight and secure.

[BOF]

My first thought when you mentioned the symptoms was that the battery voltage was going down. That seems to be contradicted by your battery measurements, but you may not be measuring in exactly the right place.

So, in addition to the stuff that Michael has already mentioned, the ECU could have a poor earth or power connection, the coil packs could have a poor power connection, the alternator might not be supplying enough current (poor power wire from the alternator or poor earth connection to the engine).

So, if, for example, there was a poor ground connection on the engine or the battery and you were losing a volt across that at load, the alternator might delivering ~14.5 volts at its terminals, only 13.5 of those could be getting to the battery (all guessed, rather 'hand waving', numbers, of course), and that would be the difference between getting the battery fully charged and getting more like half charge, which would be a poor start. Then, under load, you've got less charge in the battery than you should have and the alternator isn't really delivering, either.

Whether this loss is fully represented in the numbers that you are measuring depends on exactly where the points are that you are measuring; F-super gets its reading from some module (say, the dash controller, but it could be something else) which doesn't get its readings from exactly the same place as the coil packs get theirs.

Alt is giving me a constant 13.8V (F-Super reads 14.11V) with load, until that off a misfire then it goes down, but never beyond the battery's starting point of 12.6V.

Superficially, while that could seem a fraction low, it should be enough to keep everything going. I just don't believe that's the voltage where it counts (coil packs, injectors...maybe, even fuel pump).

Does it happen with any electrical loads apart from the lights? Heated windows ought to take more current, and so if lights do it, HRW ought to kill it stone dead, unless it is something peculiar about the lighting wiring, particularly (maybe heating/air con, as well).

Also, I'm not quite clear whether you are saying that the problem has got worse when you changed the battery. If it has, then there is a definite case for looking around the battery area for poor connection.

[craaig]

Thanks for all the suggestions! Some additional information:

So voltage drop between the alt and the battery is 0.02 on both pos and neg. And trying the best I can, the visible run of wire seems ok (they tuck in behind the two manifolds).

The symptoms are getting worse, now it doesn't need the lights to be on to stall, it does it without after developing a misfire. I pulled the connector and the fuses that serve the lights, and the engine still cuts out on its own. It appears it was only accelerated by the lights drawing electricity.

I'd decided to bite the bullet and order a coil pack as it's more economical than buying a new ECU (fingers crossed). I'll whack it on and update the thread with the outcome. I really hope the ECU doesn't fry this coil. I should probably investigate the signal before installing.

[craaig]

Just as an update, I have the coil on, and i've driven about 6 miles (broken up to 3 small trips around the local area) and it seems a lot smoother (completely resolved in fact). So if it stays this way then the coil pack was definitely the issue.