1.9 BXE engine hesitation/judder

[sef-75]

Hi there, hope someone can assist with a problem on a 2009 Passat 1.9 diesel, c.125k miles.

Original fault occurred as suddenly running unevenly, lack of power. The engine was visibly shaking like a misfire when idling and also the next morning at idle. When driving it cut out within a mile and not restart.

RAC attended, eventually started with spraying EZ start, but wouldn’t keep running at idle, but would run if revved albeit unevenly. Once warmed up just about maintained a shaky idle.

Taken to garage, who diagnosed cylinder 4 misfire from fault analyser with high positive fuel value. Injector 4 removed, sent for overhaul - wiring harness checked for resistance and OK (was renewed a year or two ago already), cam lobes checked OK, seating checked and considered OK.

Overhauled injector then refitted by garage. Cold start up and running is fine, once warmed up / after couple of miles, the engine then again has a vibration/misfire. Driving, it feels like hesitation at lower revs 1,500 - 1,700 rpm or so, especially at higher gears, but better when at higher engine speeds. Idle has a judder still.

Fault code now reads the same, cylinder 4 misfire and fuelling value+ and higher than other cylinders.

Garage couldn’t think of anything else and unwilling to spend any more time and generating even more cost, suggested taking to a diesel specialist.

They have now looked and advise the same, cylinder 4 misfire and a high positive number fuel value. Same fault reoccurs after clearing memory and test driving. Suggesting similarly either an injector or harness, but unwilling to look further, suggest returning to first garage because of warranty implications.

Any thoughts please, especially with understanding why it could be perfect and smooth when cold but juddery/misfiring once warmed up and with the fault code seem for cyl 4?

Struggling as to what might be the problem?

The garages are not wanting to be involved, so struggling with what to do next.

Thanks for any help and regards

[sef-75]

Adding the details from the print off received from 2nd garage:

P0304 combustion failure cyl 4 detected

Smooth running control quantity (cyl 1,2,3,4) -0.2, -0.9, -0.6, 1.7

Valve for unit control = Faultless control (cyl 1,2,3,4)

Unit injector correction time (cyl 1,2,3,4) -36, -38, -42, -55 uS

Smooth running control quantity (cyl 1,2,3,4) -0.8, -1.2, -0.6, 2.6

[sef-75]

Any help please?

Started again, fires up straight away, runs fine and idles smoothly when cold.

Left idling it is OK for minutes until the temperature increases towards the 70 on the gauge and then the engine increases in vibration to a definite mid-fire/judder that can be felt when sat in the car and also holding the gear lever.

Increasing revs to say 1,000rpm the engine is smooth, return to idle and it is the same a mid-fire/judder.

It seems repeatable each time from cold until warmed up, wondering could something like a temperature sensor cause this...?

[DMitch16]

Adding the details from the print off received from 2nd garage:

P0304 combustion failure cyl 4 detected

Smooth running control quantity (cyl 1,2,3,4) -0.8, -1.2, -0.6, 2.6

Could be a temperature sensor issue but don't forget that the injectors and wiring loom is inside the engine and constantly bathed in oil which gets hotter until full temperature is reached. The heat involved could alter the associated resistances of wiring etc.

This does still suggest a failing / failed injector or wiring on number 4 cyl and number 2 is not that happy either. The readings for smooth running should be as close to 0.00 as possible with a range +/- 0.50 range desirable, up to +/- 1.00 ok and anything higher, a sign of poorly performing injectors. Static readings usually indicates an issue somewhere, and an unchanging reading of 2.99 usually means the injector has failed / is unresponsive to fuelling adjustment (valve timing is mechanical, fuelling is ECU controlled).

From the idle control figures it can be deduced that 1 and 3 are in decent shape, 3 is struggling a bit and 4 is quite bad / failed.

Sometimes you will need a diesel specialist rather than a general independent garage as a lot of independents might be out of their depth with VAG PD engines. There are some very good knowledgeable recommended independents out there however that do know these engines, and you should try to find one that understands the issue from the outset, to save you time and wasted money from fault hunting / botched fixes.

Sometimes paying that little bit more for the right specialist help is worth it.

[sef-75]

Hi there,

Thanks very much for taking the time to read and reply with your thoughts.

A new wiring harness has made no difference and it is the same - fine and smooth idling and driving when cold, then the judder at idle/low revs once warmed up.
There’s plenty of power and it is smooth when accelerating/higher revs and speeds - would you expect that with a bad injector?

Just seems puzzling how it can be fine when cold and the problem develops and stays upon warming up.

Are there any specialists anyone can recommend?
I’m in Cheshire.

Thanks

[DMitch16]

Hi there,

Thanks very much for taking the time to read and reply with your thoughts.

A new wiring harness has made no difference and it is the same - fine and smooth idling and driving when cold, then the judder at idle/low revs once warmed up.
There’s plenty of power and it is smooth when accelerating/higher revs and speeds - would you expect that with a bad injector?

Just seems puzzling how it can be fine when cold and the problem develops and stays upon warming up.

Are there any specialists anyone can recommend?
I’m in Cheshire.

Thanks

I'm wondering if it is the in tank pump that might be getting hot and failing / struggling?

I'm from the deep South so Cheshire is far far away from me and I would not know any of your local firms therefore. Perhaps another member is more local and can suggest a specialist?

[sef-75]

Thanks for your reply and suggestion.

It had a new fuel pump in the tank a couple of years ago as car cut out suddenly at that time and wouldn’t restart... hence RAC & garage etc.

Googled a VW/Audi specialist who seemed to think the same things that have already been replaced- the injector wiring harness and the injector itself. Suggested going back to the original garage.

Does anyone have what the test criteria of these injectors?
Have some paperwork with data that came with the injector.

Thanks

[C_obrien4]

Thanks for your reply and suggestion.

It had a new fuel pump in the tank a couple of years ago as car cut out suddenly at that time and wouldn’t restart... hence RAC & garage etc.

Googled a VW/Audi specialist who seemed to think the same things that have already been replaced- the injector wiring harness and the injector itself. Suggested going back to the original garage.

Does anyone have what the test criteria of these injectors?
Have some paperwork with data that came with the injector.

Thanks

Ever find out the problem? Mines is doing the same

[DIYeer]

I had a similar issue recently with a BXE engine, car would run fine when cold but once warmed up would hesitate intermittently and then started to cut out.

I had originally found some suggestions online that said the crank position sensor was the fault so I swapped that out and got a cheapo one and still had the issue so I then started to look at the wiring and found wear in wiring between the crank position sensor and the ECU.

There is 3 : Red/black, blue/gray and purple.

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I found the issue here in the harness, right hand side of the engine bay. You'll have take out the airbox to get at it

39615


So I replaced the wiring for all 3 between the ECU and sensor and got a new Bosch crank position sensor €45, she's been running like a dream since