Thread: OK I still have a miss in the D2 TD5 Ideas?

No its definitely the engine dropping out just below 4000RPM. It then reestablishes for the last 200RPM, then changes.

I am beginning to think that it is that the inlet manifold is so coked up that the MAP reads overboost. I have not yet cleaned the intercooler either so that is next.

I give it one full throttle acceleration each morning going to work and it seems to be getting better. The degree of power loss seems less now than before, like it is going to 1/2 throttle now rather than completely dropping out.
Regards Philip A

Originally Posted by ramblingboy42

.5% of 4000rpm is 200......could your tacho be out by that amount thus making you think its changing up 200rpm early......it sounds like all your other operations are ok and if all is ok the gearbox is probably changing up at the correct engine speeds. i'm really not sure why you want to see 4200 on your tacho anyway.

(200/4000)*100 = 5%

But that doesn't really change the fact that the engine shouldn't miss at 4000 or 4200rpm.

It isn't that hard to get the Td5 to rev to 4000-4200rpm. If the transmission is in kick down - which is triggered by the last 5-10% of throttle travel - it will rev quite freely up to that point.

Originally Posted by PhilipA

No its definitely the engine dropping out just below 4000RPM. It then reestablishes for the last 200RPM, then changes.

I am beginning to think that it is that the inlet manifold is so coked up that the MAP reads overboost. I have not yet cleaned the intercooler either so that is next.

I give it one full throttle acceleration each morning going to work and it seems to be getting better. The degree of power loss seems less now than before, like it is going to 1/2 throttle now rather than completely dropping out.
Regards Philip A

The MAP/IAT is reads the absolute pressure in the intake manifold. There are actually two pressure sensors in the unit, one reads atmospheric pressure via a small hole in the body of the sensor and the other reads the manifold pressure.

If you haven't modified the wastegate setting at all you should see a maximum of 15psi boost or 29psi//200kpa absolute pressure. The ECU won't limit due to over boost until boost pressure goes over 20-22psi boost.

A coked manifold will restrict flow, but if the rest of the sensors and hardware are operating correctly you won't see limiting as a result of coking - the ecu should operate the wastegate to bleed off boost before that happens.

Similarly a dirty intercooler will reduce performance due to restricted airflow and reduced cooling capacity, but won't cause over boost or limiting.

If you suspect that it is the ECU limiting due to overboost then you need to look at system used to control boost. You have data collection from the engine sensor and you have the control side of the system which is the wastegate modulator, the pressure hoses connected to the modulator and the wastegate actuator on the turbo itself.

On the sensor side you have:

- MAP/IAT which gives the ECU the information required to calculate the density of the intake charge.

The ECM uses the signal from the MAP/IAT sensor for the following
functions:
• To calculate the delivered fuel limits.
• To calculate the air mass in the cylinder.
• To calculate the air speed density.
• To calculate air temperature.

In the event of a MAP/IAT sensor signal failure any of the following symptoms may be observed:
• If the MAP sensor fails manifold pressure is set to a predetermined default value and the engine performance will be reduced.
• If the IAT fails the ECM will set air temperature to a fixed value.

- AAP in the lid of the airbox which gives Ambient Air Pressure and on EU3 engines also supplies an additional Ambient Air Temperature input to the ECU.

The ECM uses the signal from the AAP sensor for the following functions:
• To maintain manifold boost pressure.
• To reduce exhaust smoke emissions while driving at high altitude.
•*Control of the EGR system.

The sensor also supplies a voltage between 0v and 5v proportional to ambient temperature. The ECM uses this signal
for the following functions:
• Exhaust gas over temperature protection.
• Turbocharger overspeed protection.

In the event of an AAP sensor signal failure any of the following symptoms may be observed:
• Altitude compensation inoperative (engine will produce black smoke).
• Active boost control inoperative.
• Turbocharger boost pressure limited to 1 bar (14.5 lbf.in2).
• EGR altitude compensation inoperative.

Without a diagnostic tool you are limited to guessing what the sensors are reading so you can't be certain if the problem lies there. However in the event of complete failure of these sensors the ECU is designed to operate on defaults that will prevent damage to the engine, so you are unlikely to see over boost resulting.

On the control side you have the Wastegate modulator, the small pressure hoses that connect to the modulator and the wastegate. Failure anywhere in this portion of the system means the ECU cannot control the wastegate and the result is over boost.

Basically the wastegate modulator controls the amount of pressurised air that is allowed to pass from the pipe at the turbo outlet to the wastegate actuator. Damaged hoses will prevent the full pressure from the turbo reaching the wastegate actuator when the modulator operates for example. Splits and leaks tend to get worse with time to the point of total failure. This can be difficult to pick up in the early stages.

The wastegate actuator is the other point of failure - a sticky actuator will cause overboost issues even if every other part of the system is functioning perfectly. Given the situation is improving with repeated use of full throttle it could be that the actuator is a bit sticky at full travel, and is loosening up with use. It might be worth checking the actuator moves freely through the full range of travel.

So basically, the failures and problems on the sensor and intake side of the equation will not cause over boost, but will cause fall off in performance. Failures in the control side of the turbo system will almost invariably cause issues with over boost.

cheers
Paul

When my head gasket blew a few months after I bought my 130 (another story), I removed it, had it skimmed, cleaned and so say blown out and cleared of all swarf (did check and blow it out again at home.. Nothing came out) and refitted it, soon after it developed a misfire... The misfire was that pronounced that it would hardly run. As I had no access to 'plug and play' diagnostics, I removed the rocker cover, cut a huge piece of cardboard to sit over the top of the engine just revealing the now open engine top. I then fired it up at idle and unplugged one injector at a time until I found the one that didn't change the engine note. (Unplugging 1,2,4 and 5 stalled it out). Borrowing a neighbours car I then paid Brendan @ British 4x4 a quick visit, bought a second hand injector of the same colour and fitted it. (I know they say you cant just swap injectors.. u can.. it did 10000 km b4 I got it plugged in without fault) Job done, we had 5 cylinders again! Be warned if you try this, you will need a BIG piece of cardboard.. 4' by 4' min, as the timing chain does throw the oil!! Knowing mine struggled to run on 4 pots much over 1000 rpm makes me wonder if you are feeling a misfire, or maybe a stuffed front pulley damper, loose flywheel or cracked backplate if its auto.. Just my thoughts.. Good luck!