Hello Guys

 

I have a wierd issue with my 2005 focus mk2 1.8 tdci with KKDA engine. When the engine is cold the idle is fine wether the AC is on or off. When the engine is warm if the AC is turned off then the whole engine shakes, if i turn on the AC the shaking stops or became so minimal that i cannot see or feel it. 

I tried to watch some live data, fuel pressure seems normal and stable, battery voltage is stable, the only thing that is jumping around is the MAF sensor g/s data, RPM is stable.

 

With AC OFF: MAF g/s between 5  and 12 - when the engine is running fine the value is closer to 5 when the shaking came it jumps up close to 9 sometimes higher. 

With AC ON: MAF g/s between 4 and 5.5

Someone said that this issue is because of the injectors, i send them over to a shop to test them all of them came back fine. EGR is written and blanked off. 

I tried to unplug the MAF sensor but no change at all. I don't have any error codes. 

I tried to send the car to some local diagnostics shops but all of them lost every idea when i turned on the AC and the shaking stopped 😄

I hope someone has some idea, or experienced the similiar issue. 

 

I'm probably wrong, but could that be the clutch in the A/C  compressor?

1 minute ago, DaveT70 said:

I'm probably wrong, but could that be the clutch in the A/C  compressor?

To be honest i didn't think about the AC compressor yet, because that's the one that solves the issue, but you could be right, can you explain your thinking ?  What should i look for ? 

That's a good shout tbh.  With the engine running and the AC OFF, look at the AC pump pulley outer ring rotating.  If it's rough or wobbling around then it's faulty.  The centre of the pump should remain still while the outer ring gets turned by the belt in this case.

If it's an old style compressor then when you switch the AC ON the pulley gets locked to the pump by electromagnet, so there is no longer the possibility for it to move independently.

New compressors are constantly variable, they don't use this type of clutched pulley system, and in that case you won't see a separate outer ring.  I'm not sure which type will be on your car without seeing it.

 

I can't see why that would affect the MAF reading though.  That was making me think it more likely to be a wiring fault, if the AC comp wiring is close to the MAF wiring at any point.

37 minutes ago, TomsFocus said:

That's a good shout tbh.  With the engine running and the AC OFF, look at the AC pump pulley outer ring rotating.  If it's rough or wobbling around then it's faulty.  The centre of the pump should remain still while the outer ring gets turned by the belt in this case.

If it's an old style compressor then when you switch the AC ON the pulley gets locked to the pump by electromagnet, so there is no longer the possibility for it to move independently.

New compressors are constantly variable, they don't use this type of clutched pulley system, and in that case you won't see a separate outer ring.  I'm not sure which type will be on your car without seeing it.

 

I can't see why that would affect the MAF reading though.  That was making me think it more likely to be a wiring fault, if the AC comp wiring is close to the MAF wiring at any point.

I'm gonna warm up the engine and remove the belt if it's the AC the problem should be gone. After i read Dave's answear i was thinking about the same thing how can the AC affect the MAF reading. Could it be that when the clutch is "sticking" the engine draws more air to stay alive ? I tried to check every accessible wires without taking the car apart unfortunatelly it's in daily use so i don't have much time to try out things, i don't find anything unusual.

9 minutes ago, kiki1337 said:

Could it be that when the clutch is "sticking" the engine draws more air to stay alive ? 

This was my first thought as well.  However a diesel car can't 'draw' more air unless the revs increase meaning more engine cycles over the same period of time.

If there's a throttle valve on your engine, that could be partially closed at idle normally.  And then opening when it's hunting in order to draw more air.  Not all of the 1.8 TDCI engines have a throttle valve so I'm not sure whether yours will or not.  Usually it is used along with the EGR valve to force the engine to draw all of the EGR gas when it can't get enough fresh air from the intake alone.

26 minutes ago, TomsFocus said:

This was my first thought as well.  However a diesel car can't 'draw' more air unless the revs increase meaning more engine cycles over the same period of time.

If there's a throttle valve on your engine, that could be partially closed at idle normally.  And then opening when it's hunting in order to draw more air.  Not all of the 1.8 TDCI engines have a throttle valve so I'm not sure whether yours will or not.  Usually it is used along with the EGR valve to force the engine to draw all of the EGR gas when it can't get enough fresh air from the intake alone.

I created a quick video from the AC in the first part it was running in the second part it was turned ott you can hear the difference and see the engine shaking. Here is the link. I think it's fine.

 

Yeah, that looks fine.

Definitely looks and sounds like a fuelling issue.  The engine will use a different 'map' with the AC off so now we've got to try and work out which sensor or actuator is changing in that situation.

If the EGR works ok, I'd try removing the blank first, just to rule out that causing issues.  (Unless it's been blanked after this fault).

40 minutes ago, TomsFocus said:

Yeah, that looks fine.

Definitely looks and sounds like a fuelling issue.  The engine will use a different 'map' with the AC off so now we've got to try and work out which sensor or actuator is changing in that situation.

If the EGR works ok, I'd try removing the blank first, just to rule out that causing issues.  (Unless it's been blanked after this fault).

It's written off from the software and blanked off, it was done after the issue.

This is strange because i belive that the fueliling issue should show itself in normal driveing but it has no problems at all unless it's idleing. The fuel consumption is great usually it's between 4-6l/100km. The only code i see regarding fueling was P0089 but it was months ago and once i removed it, it never came back.

 

Idling is more complex than driving.  The ECU is constantly fighting between not creating excess emissions but also not stalling.

Switching on the AC is likely to give the engine more fuel to cope with the extra power demand.

Difficult to know what to suggest without any current fault codes.  If you do have the throttle valve on the inlet manifold, I would disconnect the vacuum line from that (plug it with a screw) and then see if idles any better.  Make sure it is wide open when disconnected.

9 hours ago, TomsFocus said:

Idling is more complex than driving.  The ECU is constantly fighting between not creating excess emissions but also not stalling.

Switching on the AC is likely to give the engine more fuel to cope with the extra power demand.

Difficult to know what to suggest without any current fault codes.  If you do have the throttle valve on the inlet manifold, I would disconnect the vacuum line from that (plug it with a screw) and then see if idles any better.  Make sure it is wide open when disconnected.

I have to check it again but i'm 99% sure that i dont have a throttle valve. Do you think that the fuel pressure regulator can cause this issue ? I'm suspecting it because sometimes in the morning it takes a bit longer to start the engine even after i replaced all glow plugs and i'm not sure but looks like it has a tiny crack in the connector. I didn't replaced it because in the live data the fuel pressure is stable, but i saw codes before regarding this sensor. 

3 hours ago, kiki1337 said:

I have to check it again but i'm 99% sure that i dont have a throttle valve. Do you think that the fuel pressure regulator can cause this issue ? I'm suspecting it because sometimes in the morning it takes a bit longer to start the engine even after i replaced all glow plugs and i'm not sure but looks like it has a tiny crack in the connector. I didn't replaced it because in the live data the fuel pressure is stable, but i saw codes before regarding this sensor. 

Yes, the FPR (regulator) could cause an issue like this.  Though if the readings are stable, it seems unlikely in this case.  Again, that doesn't explain the changing MAF readings either.

Without a throttle valve, the MAF readings cannot change unless the RPM changes.  The only exception to that is when the turbo boosts and forces more air into each cylinder, but there will not be any turbo boost at idle RPM.

9 hours ago, TomsFocus said:

Yes, the FPR (regulator) could cause an issue like this.  Though if the readings are stable, it seems unlikely in this case.  Again, that doesn't explain the changing MAF readings either.

Without a throttle valve, the MAF readings cannot change unless the RPM changes.  The only exception to that is when the turbo boosts and forces more air into each cylinder, but there will not be any turbo boost at idle RPM.

I checked it again i dont have a throttle valve. Something changed today was a really hot day and the shaking was present while the AC was running. The sound doesn't changed like on the video but the shaking was feelable. I was unable to record any live data, tomorrow will be even hotter, i gonna be prepared and record some live data, about the maf, rpm, fuel pressure etc.. 

 

Could this be some kind of air leek in one of the hoses ? 

I was able to get some live data. The MAF value was stable at around 11 at idle. I dont saw any value chaning when the shake came. I had 2 codes today P0089-61 and P0625. I replaced the FPR today it didnt changed a thing. I tried to messure the alternator what i found is that with the AC on the battery voltage was 14.xV and without the AC and any other load it was around 13.2. I belive that this should work differently am i right ? Can this whole issue be a bad ground cable ? The alternator is brand new there was small shakes before the replace but when the old one went bad the shaking was the same as now. I'm gonna attach some images from the graph of the live data tomorrow. 

Have you run it without the belt on, to prove out it's not the compressor?

On 6/20/2024 at 8:40 AM, DaveT70 said:

Have you run it without the belt on, to prove out it's not the compressor?

Hey sorry for the late answer i was at the ford dealership for diagnostics they didnt find anything.. I tried to run it without the belt it was so much worse. They recommended an engine mount replacement it was bad i knew it, after the replacement nothing changed. 

A little heads up about the problem.

 

A lot of people said in the Hungarian forum that their car does the same thing but nobody found a solution. 

 

In the live data there is not a single value that is changeing drasticly. Without the belt the car shakes even more. The injectors had been tested. High pressure fuel pump had been replaced for testing nothing changed. 

2 hours ago, kiki1337 said:

A lot of people said in the Hungarian forum that their car does the same thing but nobody found a solution. 

I wonder if the mapping on the ECU is different for your cars than UK models?

As it shakes more without the belt, that does make it seem like a power issue.  As the alternator does not provide any power when the belt is removed.

Perhaps you could run a test of voltage and amps (if your car supports that information) to see if they are much higher with the AC on compared to it being off.

8 hours ago, TomsFocus said:

I wonder if the mapping on the ECU is different for your cars than UK models?

As it shakes more without the belt, that does make it seem like a power issue.  As the alternator does not provide any power when the belt is removed.

Perhaps you could run a test of voltage and amps (if your car supports that information) to see if they are much higher with the AC on compared to it being off.

I dont think that my car supports it. I can do a test with a multimeter if you specify what should i look for. Right now it shakes with AC too but it's not that brutal as without AC 

9 hours ago, TomsFocus said:

I wonder if the mapping on the ECU is different for your cars than UK models?

As it shakes more without the belt, that does make it seem like a power issue.  As the alternator does not provide any power when the belt is removed.

Perhaps you could run a test of voltage and amps (if your car supports that information) to see if they are much higher with the AC on compared to it being off.

I run a lenghty live data session with forscan intrestingly i found out that FUELPW (ms) goes down to 0 ms when AC is turned off. I attachted image of the forscan file i read that this is the fuel pulse with but can someone explain what it is and what can cause this ? I think it's not normal that it goes down to 0. 

Pulse width is the length of time that the injector is powered.  

So a longer pulse width means the injector is open for a longer time to allow more fuel into the cylinder.

The amount of fuel injected is also controlled by the level of fuel pressure in the rail.  So with very high pressure the injector only needs to be open for a shorter amount of time to inject the same amount as at low pressure with a longer pulse width.

I'm not sure why it's dropping to 0.  I don't think I've ever checked it on live data before.

 

Regarding electrical tests.  It's not really possible to measure amps with a multimeter.  Need a clamp meter that does around the cable ideally.  But you can test battery voltage easily.  Just put the probes on each battery terminal with the engine running.  The charging voltage should be around 14 volts.  You may find it's lower than that when the engine is running rough, a lower voltage can mean that sensors, ECU & injectors don't work properly in some cases.

20 hours ago, TomsFocus said:

Pulse width is the length of time that the injector is powered.  

So a longer pulse width means the injector is open for a longer time to allow more fuel into the cylinder.

The amount of fuel injected is also controlled by the level of fuel pressure in the rail.  So with very high pressure the injector only needs to be open for a shorter amount of time to inject the same amount as at low pressure with a longer pulse width.

I'm not sure why it's dropping to 0.  I don't think I've ever checked it on live data before.

 

Regarding electrical tests.  It's not really possible to measure amps with a multimeter.  Need a clamp meter that does around the cable ideally.  But you can test battery voltage easily.  Just put the probes on each battery terminal with the engine running.  The charging voltage should be around 14 volts.  You may find it's lower than that when the engine is running rough, a lower voltage can mean that sensors, ECU & injectors don't work properly in some cases.

Here is an image showing battery voltage on my latest live data session, lowest was 13.3V and the highest was 14.7V. 

Hmm, 13.3 is a little low.  Did it change with AC on or no difference?

On 7/5/2024 at 6:56 PM, TomsFocus said:

Hmm, 13.3 is a little low.  Did it change with AC on or no difference?

No it doesnt. I would say that the only difference is that with the ac on it's staying closer to 14V lowest 13.9 highest 14.3

29 minutes ago, kiki1337 said:

No it doesnt. I would say that the only difference is that with the ac on it's staying closer to 14V lowest 13.9 highest 14.3

Strange.  I don't think that charging voltage is quite right, would expect it to always be above 14v on a Ford of that age.  But it's not low enough to cause problems either.  Not sure what to suggest next unfortunately.