Ford C-MAX - 2004 1.8 Petrol Misfire/Hesitation - Chris M

About six months ago we started to experience a very slight misfire/hesitation. So slight that it was barely noticeable, but it has gradually got worse. It happens mainly whilst driving around town on part throttle usually when the engine is warm or nearly warm. Acceleration isn't affected and the car will pull strongly up to motorway speeds with no hesitation.Today the engine light came on and a warning message appeared, although I can't now recall what the message said. It disappeared when the car was restarted and no fault code has been captured.

Any ideas where to start looking?

Ford C-MAX - 2004 1.8 Petrol Misfire/Hesitation - Railroad.
Spark plugs and ignition coil would be the first things to check.
Ford C-MAX - 2004 1.8 Petrol Misfire/Hesitation - elekie&a/c doctor

Spark plugs ?How many miles have they done.?Pull out the coils and check for any sign of corrosion on the base.

Ford C-MAX - 2004 1.8 Petrol Misfire/Hesitation - Chris M

Thanks for the replies. Spark plugs have done about 30k, so not exceptionally old. I believe they should be changed at 40k, but obviously they can fail earlier. I'll get a new set tomorrow and can check for corrosion at the same time. Is there any test I can make on the coils whilst they are out?

Edited by Chris M on 20/11/2014 at 22:55

Ford C-MAX - 2004 1.8 Petrol Misfire/Hesitation - Railroad.
So the spark plugs have done 30,000 miles eh? Well get them out now and throw them away. No wonder you have a misfire, and carry on like that and you'll soon need a new catalyst too.

You say your spark plugs will do 40,000 miles, and I am aware that some manufacturers claim that, but don't you understand that there's a huge difference between 40k clocked up in 10 years to 40k clocked up in 6 months? In the case of the latter the plugs might well do 40,000 miles. If I were you I'd chuck your service book out the window and change the engine oil and filter, spark plugs, air filter and fuel filter at least once every 12 months. Otherwise expect to see the MIL coming on and be prepared for the expense.
Ford C-MAX - 2004 1.8 Petrol Misfire/Hesitation - Chris M

Railroad, I think you are reading what you want to read, not what is written. You appear to be reading that the car has done 30k in 10 years. It's done 90k. It's serviced at least annually. On the evidence given in my first post, please explain how the need for an oil change or the oil, air and fuel filters could cause the problem.

The plugs are NGK Iridium and are claimed to have a service life of 40-60k. Mine have done 30k and are 3 years old. Maybe they are the cause of the problem, maybe they aren't. £30 will tell and I'll post back on the outcome.

Ford C-MAX - 2004 1.8 Petrol Misfire/Hesitation - Railroad.
I'm not misreading anything. If you seriously believe that a set of spark plugs will do 30,000+ miles, regardless of how long it takes do do them then you will believe anything. The figures I quoted were examples. 30,000 miles clocked up very quickly means the engine is mainly running at optimum temperature, and the fuel/air mixture will be correct for most of that time. In this condition your spark plug's life in terms of mileage will be extended. If the same mileage takes several years to clock up then your journeys will have been much shorter and rarer. The engine will not be running at its optimum and therefore you cannot expect the plugs to last anywhere near as long. Anyone who has even the most basic knowledge of engines should understand that. Oil life, spark plug life and service life is sales pitch, and is to be taken with a large pinch of salt.

And to add to that your car is 10 years old with 10 years worth of ageing and wear. How can you possibly compare that to a new car where everything is clean and efficient?

Edited by Railroad. on 21/11/2014 at 13:47

Ford C-MAX - 2004 1.8 Petrol Misfire/Hesitation - Chris M

No I won't just believe anything, but I'll believe NGK over what you are saying:

We're talking Laser Iridium BTW.

Ford C-MAX - 2004 1.8 Petrol Misfire/Hesitation - Railroad.
Fair enough. You'd prefer to believe a manufacturer's self-claim whose main purpose is to promote their products rather than listen to basic common sense.

You have an old car, with below average mileage, and spark plugs that are three years old and done 30,000 miles and most likely way past their best. I know what I'd be thinking.
Ford C-MAX - 2004 1.8 Petrol Misfire/Hesitation - Chris M


The change of spark plugs has made no difference whatsoever and absolutely no signs of corrosion anywhere. To recap, the hesitation is very intermitent, usually occuring around 30 mph, on partial throttle, when the engine is warm.

Edited by Chris M on 06/12/2014 at 12:36

Ford C-MAX - 2004 1.8 Petrol Misfire/Hesitation - Railroad.
Check manifold vacuum using a gauge for an air leak. There is lots of useful information on the internet to tell you how to use it and what to check for.
Ford C-MAX - 2004 1.8 Petrol Misfire/Hesitation - Chris M

Thanks Railroad. I'll investigate.

But one question. Why would a vacuum leak cause an intermittent fault as I'd have thought the leak would always be present?

Ford C-MAX - 2004 1.8 Petrol Misfire/Hesitation - Railroad.
Because manifold vacuum very much depends on engine load and throttle position. The engine management system monitors manifold pressure via the MAP sensor, and is the most critical part of the system as far as fuelling is concerned. A vacuum gauge is a very useful tool when diagnosing engine running problems. Alternatively you can use a scantool reading MAP sensor live data. Just be mindful that most scantools display pressure in KPa, and a reading of 100 is atmospheric pressure. Expect a reading of around 40KPa at idle, but more importantly the reading must be steady. A fluctuating reading indicates a problem such as a misfire or sticky valves.

Check out this site for more information.
Ford C-MAX - 2004 1.8 Petrol Misfire/Hesitation - Malcolm J

We have a 2005 C-Max doing exactly the same, and it has been using a stupid amount of oil, so I plugged my OBD Scanner in

Cylinder 1 is miss-firing and there has been error codes for primary and secondary circuits in A, B, and C Ignition Coils,

1st Question, how much oil are you using?

Have you tried a compression tester?

I'm 90% sure ours is going to be a strip down, this will be confirmed when I get my compression tester back from a mate I lent it to.

Ford C-MAX - 2004 1.8 Petrol Misfire/Hesitation - Chris M

Malcolm J.

We got rid of the car 2 years ago to a friend who ran it until recently.

The issue turned out to be the throttle body. New one required. I thought had posted an update but I can't find it. The car used very little oil and ran very nicely following the repair.


Value my car