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Thought I'd share my recent experience of resolving issues I've had for a long time with my 2004 1.8 petrol C-max that I've had for over 14 years in case it helps any other owners...
1. The high revs when cold became noticeable years ago after cleaning the throttle body to fix poor running and performance (which it did). I did the usual like looking for splits in oil breather (limited vision between inlet manifold) and all other vacuum pipes. Tried spraying WD40 etc to see if revs would increase, but no and revs always went back to 750 RPM when warm. Replaced throttle body (second hand and now have spare if someone needs one!) and cleaned TMAP. All no joy. Put up with it for years as really no issue when car warmed up. Being in lockdown decided to remove the PCV oil breather tube to check once and for all. From other posts it looked like I had to remove inlet manifold, but someone did mention that you could get it from below if you remove the starter motor - I did this saving hours and found 3 inch split in hose which could not be seen - result as revs seem better. Only issue is the £47 price tag for a 5 inch piece of rubber!!
2. Had intermittent alarm triggers for years until replaced main battery when car was 11/12 years old - not bad for the original. Started again recently at night annoying me and neighbors. The voltage does seem a little low but starts fine. Just identified fuse F57 for the alarm horn under the wiper scuttle and removed fuse so if it does trigger there is no beeping! Another result.
Happy fault resolving :)
 

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Edit to above... The alarm still goes off! So please ignore the fuse number given! Just need to find the location of the alarm horn and disconnect - it's not behind the windscreen motor under the scuttle where I expected to find it - doh!
 

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Edit to above... The alarm still goes off! So please ignore the fuse number given! Just need to find the location of the alarm horn and disconnect - it's not behind the windscreen motor under the scuttle where I expected to find it - doh!
Final Edit - the alarm horn is in the rear of the car drivers side under the large internal plastic trim, towards the top at the rear door end. Now disconnected and silent when triggerred. Just the flash of indicators for 5 minutes which I can live with!
 

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This screams of sticking or leaking injector, (asin just one), my first car was a 1.8 Escort Ghia, little rocket ship back in the day, but i suffered for 2 years with a car when cold that would rev its nutts of when sat idle in traffic, or worse, pull the car whilst breaking.

In the end and at my wits end, i took the injectors out, run them down to a truck workshop, and got them to test them for me, as soon as pressure hit the rail number 2 was leaking and jamming in the OPEN position, so just pissing fuel thru it.

If you have an ODBII Scanner and appropriate app, load it up, and setup to see, injector pulse width, injector pressures and rail pressures. Any leak will be clearly visible, a slow injector will have a PWM much wider than others.

Any leaking injector will have a constant low pressure relative to the others

Any rail issues will be visible because the rail will not hold pressure in a "smooth" manner, the peaks and troughs will be all over the place.

You can also check by viewing the LONG TERM FUEL TRIM, if you have a leaking injector, the ECU will be constantly making up for a fuel rich condition, and if the LONG TERM FUEL TIME shows its making up for a lean condition, then it could be a slow to fire injector.


Can i test the injector myself.
Yes, however you wont to the naked eye,see if an injector is slow to operate, simply remove the injector from 1 cylinder, and place it into a cola bottle, so fuel is sprayed into a bottle, and turn the car over, if it fires up dont panic, allow run for a few seconds and switch off, check bottle for result.

Mark the bottle to show how much fuel, and repeat on other injectors, a bad injector will flow less relative to the others, and a leaking injector will flow more relative to others.

If you do test this yourself, Do it in a WIDE OPEN SPACE, on a Breezy / Windy day, atomised fuel coming out of the injectors is BEYOND FLAMMABLE, it will combust if so much as gets a sniff of ignition, make sure the injector is fireing into a container with as little leakage as possible. I can not stress just how flammable hot vaporised fuel is

Okay, so why does this problem go away when the car is heated up

Thermal expansion, allows for a "free'r movement of the injectors internals, and thus run better (or even seal better)
 
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