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Discussion Starter #1 (Edited)
1.6HDI stammering under acceleration (but only randomly)

Now, I know diesels don't technically "misfire" - but that's how it feels. Here's whats been happening:

  • Few weeks ago - accelerating gently, the car dropped power instantly, then straight back on the power. It was like a momentary loss of all power for a split second. When it happens on the throttle, it gives a fair "thump" as the engine cuts and kicks back in.
  • Then... nothing. Flawless.
  • Last week, motorway driving after about 2 weeks trouble free, it gave a "bump" 3 times on the way home. These all happened on flat throttle at 60-70mph. Asides from those split seconds, the car is perfect. Revs out well, pulls well.
  • Then, 3 days ago, went to start the car in the morning and it took 2 cranks to fire.
  • 2 days ago, car wouldn't start after sitting. I used the hand primer bulb, it fired up no problem. I could hear air in the primer. It had lost pressure.
  • Mechanic looked the car over and sees no problem. No visible leaks. My injectors were all flow tested last year with new seals.
  • Today, it wouldn't start on the key but with 3 squeezes of the primer bulb, started no problem. I drove it for about 10 miles with a stop at the shops. No problem - but I'm sure that tomorrow morning, it'll need a prime to start.
So... any ideas? The "bump" in power is very intermittent and I can't provoke it. When it happens, its usually on flat/light throttle but once, it happened under fairly quick acceleration.

I have PP2000 here so can test out specifics if you can guide me the right way. Its an old version, but works ok. I've ordered a new fuel filter, just in case its in need of changing.

Car details:
2006 407 1.6HDI with 113k on the clocks.
DPF is not clogged (% pressure is healthy), new Eloys fluid done last year

Any pointers gratefully received! :thumb:The car has been pretty flawless over my 7 years of ownership and I don't want to have to get rid unless really forced to.
 

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I'd be looking for leaks inbetween the fuel tank and the HP pump. If you need to prime it daily, then too much fuel is flowing back to the tank, and air is getting into the system. All it takes is for a pin-prick hole in a pipe.

Planet/Diagbox should be able to tell you cranking fuel pressure. Approx. 400mb is what you're looking for.
 

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Discussion Starter #3
I'd be looking for leaks inbetween the fuel tank and the HP pump. If you need to prime it daily, then too much fuel is flowing back to the tank, and air is getting into the system. All it takes is for a pin-prick hole in a pipe.

Planet/Diagbox should be able to tell you cranking fuel pressure. Approx. 400mb is what you're looking for.
The only thing I have is Planet - any idea where the menu path is to watch the fuel pressure values?
 

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Discussion Starter #5
Cheers - I'll give that a go in the morning when its been sat overnight. I take it the fuel lines from tank to pump can be inspected from underneath?.. Might take a run back to the local garage and get it on the ramp.
 

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Discussion Starter #7
Hooking up PP this afternoon and will get these lines checked.

It needed a couple of primes this morning, started fine. Drove 3-4 miles no problem then decided to rev it out a bit to see could I provoke this "miss".

2nd gear pull - no problem to 4k, 3rd gear, BUMP. Its as if the car ran out of pressure... and needed a split second to recover.

I guess a joint leak would perhaps let air in under acceleration? The two problems must surely be linked.
 

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Discussion Starter #8
Right... well, Its for the garage tomorrow but in the meantime:

1. Fitted a new Bosch fuel filter
2. turbo inlet washer (the big orange/red one) was perished so I replaced that

Car was driving well.. but is still stammering/missing. Driving gently its ok.. rec in 2nd up to 4k and on accelerating up in 3rd.. BUMP.

I have no engine lights and PP scans up clean. Pump pressure is healthy so its not the fuel pump. Cyl 3 injector is a bit wet - ie. a little pooling of diesel on the head.. but not a lot. I had all injectors tested last year and new washer kits on reinstallation.

Could this be the EGR? The car is starting ok after sitting - so my main issue is this random stammering.
 

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I had spmething similar but under different circumstances, mine was when accelerating away from stationary. A can of wyns EGR cleaner sorted out the loss of power that I experienced for a split second but I didn't have the priming issue you have so may or may not work in your case. It's not too expensive so maybe worth a punt and can't do any harm. If you do use it be warned that it makes the engine sound as though all the bolts have come loose and are rattling around inside the engine. It can be a frightening experience first time round
 

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You remove the maf on the air intake pipe and squirt short 1 second blasts into the intake. The engine picks up revs and you wait till it settles down before the next blast. After using about half a tin you rev the engine to about 2k for a while then continue till the can is empty.
 

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If there is diesel on the head it could be a perished bleed off pipe or top of injector is loose. This will let air into system and give a slight miss fire when running as the small amount of air renters the pump as it gets back into fuel lines where leak off pipe rejoins fuel lines on fuel filter.

It may also over night leak enough air into the system for you to have to prime it to start. All the symptoms you have
 

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Discussion Starter #13
Well.. the saga continues.

Turns out my mechanic took the EGR off when it was in the other day - and it wasn't in too bad a state at all.

I bought a used one, just in case. Only cost £30.

Meanwhile... after the new filter in and a good drive last night - the car completely refused to start today. The normal 3-5 pumps of the primer did nothing. In the end, it took a mammoth priming session to get it back up to pressure. Whatever was letting in air is REALLY letting it in now.

Drove the car back to the garage and there it is.

Investigations start again tomorrow - fuel lines as advised here and I sent him a copy of your message windy1603. Although these 2 problems are different - they are surely connected - so that idea sounds well worth investigating.

Fingers crossed he spots something tomorrow. There are no low mileage 407 2.0HDI's on the market right now in NI, so I need my 1.6 to die another day!
 

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Discussion Starter #14
We couldnt prime the car at all today. Doesn't matter how much... it wont pressurise.

Up on the ramps - visual inspection of the lines from the tank... EVERYTHING is bone dry.

Ended up taking off all the fuel pipe harness up at the engine side - the harness including the primer bulb. When you tried to prime the lines.. you could hear air with EVERY pump. We reckon the pipework is drawing in air somewhere.

So... new pipework loom required! Seems a set new will run you about £75 on eBay. Will try the local breakers in the morning and dealers (for a laugh).

If this doesn't work... its for the scrapper. Noisy turbo. Chirping flywheel... its days are now numbered.
 

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Discussion Starter #15
Posting back just to close this one off...

Ordered a 2nd hand set of fuel lines, but they were the wrong fit. Sods law. According to service box, there's 2 types of lines for the 1.6.

So - I've called it a day. £120 for new lines that MIGHT fix the problem isn't worth spending. The DMF is on the way out and the turbo is getting loud. Its got damage to one or 2 of the vanes/fins. I suspect the 1st time the red rubber seal to the turbo perished, it sucked up some fragments.

I've thrown the towel in and bought a 2.0HDI 407 to replace it.

I'll be breaking up the 1.6 as its been well kept over my ownership. Even if I got it running, it'd be hard to sell with the noisy clutch/DMF and I can't be bothered with the hassle of buyers off Gumtree complaining.

It owes me nothing after 8 good years of service. It is getting towed home tomorrow where I'll strip off the good bits before calling in the scrap man.

 
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