Enigine missing when over 3,500 revs!

Hi All
New here so please be gentle!! Just acquired a 2001 TD5 manual, On high'ish revs the engine starts missing and holding back. Drove 160 miles a couple of days ago, it cruises along 65mph very well but on pulling away when the revs get above about 3500 in any gear the engine starts jolting and (if it were petrol it feels just like spark plugs breaking down) if you know what I mean.. Any help would be most grateful.
Cheers

maybe over boosting and ecu cutting fuel as it goes into limp mode

My guess would be possible fuel pump failing, mine done this to start with then just died.

Thanks for the suggestions, I will have a good look round it
Cheers

Could be any one of the following:

1. In-tank fuel pump failing;

2. In-tank fuel pump filter blocked with black goo;

3. Turbo wastegate modulator failing.

4. Air filter blocked/knackered.

5. MAP on the inlet manifold blocked with black goo.

Good luck

Dave

Hit the filter first then if no difference test fuel pump pressure.

mine did this at 3500 revs new maff sorted

Sorry, complete ignorance here.... What is a maff?

Cheers

Mass Air Flow Sensor, it sits in the air intake system and measures the flow of air going into the engine

Thank you... So it's not the ministry of agriculture, fisheries and food then !!!!

Disconnect the plug to the maf and see how the car drives after that to check if the maf is faulty. If it drives ok then the maf is goosed, if you still have the problem then it's else where.

Check vacumn tubes to the waste gate mod. and turbo. Small split in one of mine caused a misfire

Check leak off pipes on injectors. Then take them off and get some one to turn engine over. If fuel squirts out very rapid then the injector its coming from is goosed. crude but easy way to check them. All pressure should be going to the injector on start up. A little leak off and I mean a slight dribble is ok. But If it squirts out then the injector isn't getting the right pressure and it's returning to the tank. This problem should come with a slight diesel knock. ( tapping sound )
Good luck

John FHA said:

Check leak off pipes on injectors. Then take them off and get some one to turn engine over. If fuel squirts out very rapid then the injector its coming from is goosed. crude but easy way to check them. All pressure should be going to the injector on start up. A little leak off and I mean a slight dribble is ok. But If it squirts out then the injector isn't getting the right pressure and it's returning to the tank. This problem should come with a slight diesel knock. ( tapping sound )
Good luck

Click to expand...

It's a TD5 so all the injector leak offs are channeled through the head so you can't see them.

minidod said:

Disconnect the plug to the maf and see how the car drives after that to check if the maf is faulty. If it drives ok then the maf is goosed, if you still have the problem then it's else where.

Click to expand...

I've heard this a number of times but I can't see the sense in it myself, plus the TD5's with faulty MAF's that I've worked on didn't behave like this.

The MAF gives air volume and temp info to the ECU, in order to optimise fuelling. If the MF doesn't work it gives out no info. As a result the ECU defaults to a std table of values.

Therefore logically speaking, if the TD5 is running with a faulty but connected MAF, the engine will run on it's default map - disconnecting the MAF will not change this so there will be no change in engine performance.

There is only one sure way of identifying whether the MAF is working or not and that is to connect it to a diagnostic terminal to read the MAF outputs.

This is what I have done on many occasions and none of them show up erroneous readings, they either work properly giving variable readings at different throttle inputs/revs or they give a fixed, faulty single reading.

So to summarise, if a MAF is faulty I would expect there to be no change in performance whether connected or not.
Cheers
Dave

thebiglad said:

I've heard this a number of times but I can't see the sense in it myself, plus the TD5's with faulty MAF's that I've worked on didn't behave like this.

The MAF gives air volume and temp info to the ECU, in order to optimise fuelling. If the MF doesn't work it gives out no info. As a result the ECU defaults to a std table of values.

Therefore logically speaking, if the TD5 is running with a faulty but connected MAF, the engine will run on it's default map - disconnecting the MAF will not change this so there will be no change in engine performance.

There is only one sure way of identifying whether the MAF is working or not and that is to connect it to a diagnostic terminal to read the MAF outputs.

This is what I have done on many occasions and none of them show up erroneous readings, they either work properly giving variable readings at different throttle inputs/revs or they give a fixed, faulty single reading.

So to summarise, if a MAF is faulty I would expect there to be no change in performance whether connected or not.
Cheers
Dave

Click to expand...

I can see where you are coming from but in my experiance when the MAF went on my Disco it had a flat spot and slight miss fire. Cleaned the MAF with contact cleaner from work and made no difference. Once I disconnected the MAF it ran fine but used more fuel as the default MAF settings don't work with the remapped ECU.

If the MAF is faulty it is still highly likley that it will be sending signals to the ECU but the wrong ones and hence the misfires and other problems being experianced.

MAF's can also be affeceted if you are running a K&N or other oil covered filter that has been over oiled.

minidod said:

I can see where you are coming from but in my experiance when the MAF went on my Disco it had a flat spot and slight miss fire. Cleaned the MAF with contact cleaner from work and made no difference. Once I disconnected the MAF it ran fine but used more fuel as the default MAF settings don't work with the remapped ECU.

If the MAF is faulty it is still highly likely that it will be sending signals to the ECU but the wrong ones and hence the misfires and other problems being experienced.

MAF's can also be affected if you are running a K&N or other oil covered filter that has been over oiled.

Click to expand...

Hi MD, I reckon I've checked perhaps 25 TD5 MAF's over the last couple of years and in that time I've never found one that is faulty and still sending out signals.

As I said before, they either work properly or they don't work at all.