More Mondeo problems....

Well assuming the connecters not buggered it's got to be worth trying a new oxygen sensor. & 186 is probably a consequence of 172

Thanks Duncan..... I hoped that 186 was a consequence of the oxygen sensor. I think that I'll check the wiring out again for the Oxygen sensor as it is only a month old.

Thanks again, Mark

it cold also be that the leads are breaking down they had a habit of doing this and giving out all sorts of fault codes because you can't code a crap lead :)

'Scuse my ignornce but how do you get these codes ?? Stuart

Hi Stuart,

Gunsons make a fault code reader that plugs into a special socket to receive the fault codes from the ECU. You can also perform things like wiggle tests to check for faulty leads, relay checks to activate all under-bonnet relays and power balance tests which cut out each cylinder in turn and report which cylinder gives the worst performance.

Well worth the money, IMO, but I think that you would probably get away with an analogue voltmeter.

Check out the haynes manual - it's all explained in there ;-)

Cheers, Mark

Plug leads? If so, then yes - it's an option that I hadn't considered. I last changed them three years (54000 miles) ago so they're probably long due replacement.

Thanks, Mark

No! your treating the symptom not the cause! Code 186 is the dead give-away. What makes the ecu open the injectors for longer than it thinks it should AND leads to the o2 sensor reporting a leak mixture?

All together- an air leak!

Check the inlet manifold for vacuum leaks- especially the rubber elbow under the coil pack, the heater recirc hose, and the EGR connection if fitted. Also check inlet duct from MAF to throttle body. Check all PCV hoses for splits or leaks.

If you find none- go to the exhaust manifold. Or any point in it that will admit air before the o2 sensor thats unmeasured. Does this engine have

Tim..

If it's a 2 litre (I think they're the ones most at fault), then statistically, you're doing very well to make them last that long!

However, touching serious quantities of wood here, mine were replaced 93k miles ago with Ford ones, and they're still going strong.

Given your descriptions of flat spots, I'd have definitely said leads, but I'm not 100% sure when you mentioned the idling problems, (but that could be down to lead failure -> Incomplete combustion -> O2 sensor being confused.

Remember though : Ford leads only. Maybe Bosch. _No-one else_ - you _will_ have to replace them. 80kV wasted spark system sees to that!

Pete.

Mark, Replace the throttle body assembly.......too rich, too lean ... this is common problem.... especially with the fiesta.

JK

Thanks Tim,

I've heard no air leak - but I guess that it's not improbable that the engine will drown out the noise.

I'll have a look over the weekend to see what I can find. Hopefully I can trace the source of the problems.

Thanks again, Mark

Thanks Pete,

It's a 1.6.

The idling problem is only seen occasionally. There's quite a specific pattern to the change in revs which makes me believe that it is under the control of the ECU. I think that Tim's onto something here as the ECU seems to be confused as to the sensor readings and tried to over compensate.

I'm not going to rule out the leads as they are getting on a bit, but I'll investigate the air leaks first.

Cheers, Mark

Hi JK,

Is there any way to clean this? It's never been touched before, so it may be worth a look.

Cheers, Mark

Yeah.... clean it with brake cleaner..... aerosol type ..... however this may not help... if you can ..then replace the body.

Also Mark....on the bulk head to the left.... there is a small unit with 2 vacuum hoses going into it.... approx 70mmx40mmx15mm, silver aluminium with a multiplug on it .... if your car has it fitted then this was a bastard for causing strange running concerns...... it is a unit for sampling exhaust gasses and was a real pain in the arse..... If your car has it fitted.......REPLACE IT....... only a certain build time frame had them fitted but it was a problematic component. Hope this helps.

JK

Only cars with EGR use this component- its the Exhaust Differential Pressure Transducer and yes they do go faulty.

Does your car have EGR?

Tim..

Hi Tim

Yes it has EGR - is there any way to test this unit? The Haynes manual says not for the DIY'er :-(

Cheers, Mark

Using Linux - no registry, no worries ;-)

Erm. Well. If you can't "borrow" a DFTE sensor to try, what you can do is disconnect the vacuum hose from the EGR lift diaphram and plug it. Try the car. If it now behaves perfectly then you do have a fault with the EGR system and the most likely cause of it, (if all other visual checks of hoses and for leaks reveal nothing etc) is a failed DFTE.

They are around £80 and the dealer should keep it instock!

The only other thing is a stuck open EGR diaphram which is open even with no vacuum applied due to carbon build up- it may be wise to dismantle and check it to be on the safe side. Tim..

Thanks Tim,

You've given me more than enough to look at this weekend now. Hopefully it'll be something cheap like the diaphram needing attention. All in all, I think that I've had to spend out more on the car than it's worth over the past few months :-(

Thanks again, Mark