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Ogola89

Flat Spot and smoke when accelerating quickly or engine under load Ford Focus Zetec 1.8 disel 08 Reg

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Hi All,

Firstly, I apologise, if the term 'flat spot' is an incorrect term to use in this context. However, I have a bit of an issue with accelerating on my Ford Focus 1.8 Zetec 2008 reg (diesel) with a duratorq engine.

If I rev quickly (and need an increase of airflow quickly), the car tends to get a flat spot about 1800-2100RPM between gears 3-5 when under load only (when on an incline - there is no problem when driving flat or downhill), and it billows out alot of smoke. If I accelerate slower, there are no problems and the car drives quite well. However, going up hills, I get a flat spot between 50-70mph depending on the incline of the hill, and have to slow to a speed just slightly below the flat spot. 

Also, when stationary, in neutral, high revs (2400+) create a sooty black smoke, and alot of it.

A friend of mine is a mechanic and we did some investigation, we cleaned and replaced the air filter, cleaned out the EGR valve, and although dirty, there isn't much residue there. We also checked the turbo fan and it was fine, very clean, checked for tears in the pipes around the engine, especially those relating to air intake, and found nothing. 

We also checked the voltage of the MAP sensor, which was working, but did not seem to be registering any increase of electrical activity when accelerating, and thought this would have been a problem. However, when using a suction guage, we found that there was barely any suction coming to the valve attached to the MAP sensor, and so this is probably the case that there is not enough suction to register an activation of the MAP sensor to boost airflow. This goes in hand with the air inlet from the filter, which does not get as 'hard' as it needs to during acceleration.

The oil has been changed and the filter replaced, but still the problem persists, and I don't know what else could be the problem.

Does anyone have any experience with such a problem and is able to help me diagnose it?

No warning lights on the dashboard and diagnostic tool indicates potential problem with glow plugs and air intake.

I have recently bought the car - it had 85k miles on the clock, timing belt had not been replaced. Reg is NJ08 0NX

Thanks!

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Sounds like you've checked most things tbh!

Did you check the MAF as well as the MAP?  What was the specific air intake fault code?  Underboost?  The intake pipe from the filter is under vacuum when on boost so shouldn't be hard, boost pipes after the turbo should be hard. 

Could be faulty injector(s), the 1.8TDCi has a common fault with them around 2008/09.

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On 11/13/2017 at 10:23 AM, Ogola89 said:

We also checked the voltage of the MAP sensor, which was working, but did not seem to be registering any increase of electrical activity when accelerating, and thought this would have been a problem. However, when using a suction guage, we found that there was barely any suction coming to the valve attached to the MAP sensor, and so this is probably the case that there is not enough suction to register an activation of the MAP sensor to boost airflow.

The MAP should have about 1.6v on its signal line (White wire on my car) with engine stopped (ign on) or low revs. As the turbo comes in, it should rise to over 3.2v, which would be 1 Bar (14.5PSI) of boost, maybe up to 4v at 1.5 Bar (22PSI) of boost.

On the 1.8TDCI, as with most diesels, there is no throttle, so there is hardly any suction in the air system. Just the loss over the air filter, which should be quite small. A combination of accelerator position & RPM determines the turbo boost, the MAP then measures this.

You will not see much boost when revving the car out of gear, only when working under load.

The 2008 injector problem symptoms are typically hesitation under acceleration, followed by the MIL with injector error codes.

I assume the fuel filter has been changed. You could try un-plugging the MAF, sometimes no MAF works better than a faulty one.

A failed EGR actuator might cause a problem like this, if the EGR was sticking open, but it does not sound like it to me (my EGR actuator has been faulty, and repaired, on & off all over the last 4 years or more!) Blanking the EGR is easy and would eliminate this possibility.

If it does seem to be injectors, also be aware of the fact that the lower timing belt needs changing on these cars before 100k or 10 years. This is quite a bit more expensive than the upper belt, and has been known to fail well before 100k miles.

(The 1.8TDCI before 2007 had a lower timing chain, which has very rarely been found to fail.)

 

 

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