Jerking under “hard” acceleration

**lyhoon94** · 1st October 2017, 05:55 PM

Hi all!

In for another dose of advice from the D2 gurus regarding 2 issues.

As of recent, the mrs has sold her car and has been driving the disco around as her every day until she saves up for her next car (hurts me on the inside but when life gives you lemons, you make lemonade).

She has told me of an issue where the car just dies randomly.

The first time the car died, she was in a maccas drive-thru. A couple of friendly strangers pushed her back out of the drive-thru where she sat until RAC came and jump started the disco. The second time she was on a Main Street and broke down next to a servo. I came along with a jerry can some jumper cables, tried fuel first to no avail then jumper cables which got it going eventually.

I initially thought it was her not taking care of it e.g making sure there’s always fuel, not leaving interior lights on when you walk away and so on. I also didn’t have much to go on but she eventually figured out that when ever the car won’t start, she just goes to open and close the boot door and the car will start again.

Any ideas on this one?

The second issue I seek advice on comes from my recent trip down south from Perth to dunsborough.

Over the 3 hour drive home, sometimes under hard acceleration, the car would accelerate normally until it reached 3000 revs and then just stuttered until you either let off the gas and then accelerated again where it then proceeded normally or put your foot flat down through the stuttering and it would shortly stop.

This happens intermittently at all speeds, in or out of sport mode and whether rolling or from a stand still.

My first impression were it was 3rd gear slipping in which case would be an auto gear box service. Am I close? What are your thoughts?

Thanks in advance for any help.

Picture take while on 3 bears track for your attention.

**rangieman** · 1st October 2017, 06:29 PM

Petrol or Diesel ?

ScotchRocks · 1st October 2017, 08:04 PM

You are describing exactly the symptoms my Td5 had before the fuel pump died.

If you can pressure test at the fuel temp sensor you should get 4 bar, but are probably getting less.
See this video:
Td5 Non Start Problems - Part 2 - Testing the Fuel Pump Electrics and Pressure output - YouTube

At higher rpm the mix is too lean and power vanishes.

I note that I had no fault codes when this happened.

**lyhoon94** · 1st October 2017, 11:01 PM

Originally Posted by rangieman

Petrol or Diesel ?

Thanks for replying Rangieman.

I’m rocking a 2001 td5.

**rangieman** · 1st October 2017, 11:15 PM

Originally Posted by lyhoon94

Thanks for replying Rangieman.

I’m rocking a 2001 td5.

Now oil in the loom im guessing it has been replaced and checked yes

And yes the fuel pump could be a suspect any unusual noise ?

Boost modulator bypass to eliminate

**lyhoon94** · 1st October 2017, 11:21 PM

Originally Posted by ScotchRocks

You are describing exactly the symptoms my Td5 had before the fuel pump died.

If you can pressure test at the fuel temp sensor you should get 4 bar, but are probably getting less.
See this video:
Td5 Non Start Problems - Part 2 - Testing the Fuel Pump Electrics and Pressure output - YouTube

At higher rpm the mix is too lean and power vanishes.

I note that I had no fault codes when this happened.

Thanks ScotchRocks, this has helped heaps.

I will sus this out and report back.

Very much appreciated!

**lyhoon94** · 1st October 2017, 11:28 PM

Originally Posted by rangieman

Now oil in the loom im guessing it has been replaced and checked yes

And yes the fuel pump could be a suspect any unusual noise ?

Boost modulator bypass to eliminate

Loom looks to be fine, was replaced was the previous owner.

No unusual noises being called out but will investigate the pressure as suggested.

Boost modulator bypass to eliminate - what does this mean? As in I could eliminate the problem by bypassing the boost modulator? If so I’m guessing the potentially failing fuel pump would still fail eventually?

**Pippin** · 2nd October 2017, 09:07 AM

"I initially thought it was her not taking care of it e.g making sure there’s always fuel, not leaving interior lights on when you walk away and so on. I also didn’t have much to go on but she eventually figured out that when ever the car won’t start, she just goes to open and close the boot door and the car will start again."

Sounds like it is definitely the fuel pump.
Nick

**sam_d** · 2nd October 2017, 09:27 AM

I had similar problems recently.

Bypassing the boost modulator helped a lot at the time. Disconnect the tube that runs from the intercooler to the waster gate modulator and run a tube from the intercooler pipe directly to the waste gate actuator.

The waste gate modulator is a fairly cheap part to replace but it's worth checking that it is the problem first.

I also had an iffy MAF which didn't help but since replacing the MAF I've not reconnected the waste gate modulator yet but everything seems to run just fine now anyway. I'm not racing my Disco so I'm in no rush to check how it goes with the waste gate modulator reconnected.

**JR1** · 2nd October 2017, 04:56 PM

Jerking/surging under acceleration around 2800-3000rpm sounds like boost modulator. I knocked one of the hoses off mine a few months ago when replacing the engine mounts.

As for the starting after closing the back door-Reminds me of an old commodore i once owned. When it wouldn't start, I had to climb underneath and bang on the fuel tank to get the fuel pump to kick in. Perhaps the back door slamming is enough to bump the pump into action.

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