1.6 hdi lumpy cold start - SOLVED!

[Sol]

Hi folks, 

I'm back on the forum after a long break with another m59, an 07 1.6 hdi this time. It's a wee trooper, but since I've had it, always (almost) lumpy as heck when first started, even in mild weather. I was going to do the glow plugs, but saw a few posts where this did not fix the issue even though first instinct is to blame the plugs.

Does the 1.6 DV6 have a waxstat or if not, what's its cold start method for fast idle control? My old 1.9d had the wax stat issue and I fixed it but this engine looks totally different of course.

When the 1.6 is started, its really lumpy even when held at 2k rpms, after a minute or so it's smooth as butter. It never seems to have any fast idle setting when cold, except for a couple of times when it has mysteriously started perfectly and ran like a Swiss watch from cold, idling a bit above normal idle nearer 1k rpms. Normal warm idle looks like a tad over 800 rpm.

It never fails to start of course, just mostly lumpy as heck till it warms up a bit.

[polar]

My 1.6hdi has always been lumpy when cold since new but no smoke so ive never bothered mentioning it, still the same ten years on.

There is no wax stat because its a hdi the ecu controls everything via sensors.

Have you done the basics like filters. How many miles - this is always important to mention.

Glow plugs would be my first port of call anyway at the age of the vehicle.

Other than that a diag would be a good move - done by someone who knows how to read the parameters - it could be a temperature sensor lying - air or coolant?

[Sol]

Thanks for the reply mate. It's got 56k miles, full service history from new (one single owner before me, my employer!), Recent full service 2 months ago. Lived a charmed life as a van to take teaching materials to schools by learning support officers, so was never abused. I'm pretty strong on diagnostics but don't have Lexia yet. I'll scan it with vagscan and see if anything useful turns up. Temp gauge works so CTS probably fine. Just wasn't familiar with the 1.6 hdi motor before now hence the wax stat question. Does anyone know what the fast idle arrangements are on the DV6?

I had initially blamed the glow plugs as this would immediately be my first call, but others with the same symptoms found it didn't help. Will test them at the multiplug first anyway.

Being then a modern hdi, I guess it will be dbw and the ECU will use the throttle body motor to up the idle speed when cold. Does it have more than one CTS?

[jj9]

I bet the glow plugs are knackered, check them and see.

My car had a rough tick over from cold that went off after 30 seconds or so, all four glow plugs were off, new set of plugs and the problem was gone.


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[Sol]

Good stuff, thanks lads for both your help and suggestions. I'll bite the bullet and do the plugs

[polar]

Yes it has three temp sensors think including air temp sensor.

But as jj says im still with glow plugs - check good idea

[jj9]

Good stuff, thanks lads for both your help and suggestions. I'll bite the bullet and do the plugs

Make sure you limber up well before you start as it helps if you're a contortionist 

Remove them when the engine is hot, and make sure to be very gentle with there removal, you have to tease them out a little at a time if you don't want a nightmare on your hands.




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[polar]

https://www.youtube.com/watch?v=qefjCCHx5t0

[geoff]

I'd try putting a healthy dose of injector / fuel system cleaner through first as you may be lucky with a simple and effortless fix.

Another one is to check the air inlet connector at the turbo - dead quick and simple - where the hard plastic duct from the flter terminates at the turbo there is a flexi rubber.
I had lumpy starting and a little puff of fumes on initial startup and this rubber had developed a split, new rubber solved my issue. In my case the servicing dealership had missed the split rubber.

edit : the rubber fix also boosted MPG as the air flow sensor wasn't able to read correctly with the split rubber as air flow was by-passing it

[ffrenchie]

On our friend's car we just did a continuity test on the heaters with a light and replaced the two that didn't show a light which cured the problem. You are not touching the accelerator before starting the car ?