LUMPY/KNOCKING NOISE WHEN 1ST START

[seanh01]

HI All,

My car a 406 2.0 HDI 90 bhp 02 plate Turbo Diesel, it has a lumpy start when you first start it in the morning just for a few seconds and runs fine, after that initial start,it starts fine, it's hard to describe in writing, but it's like it's a jack hammer feel to it, and when I started it last night
from cold it made a very metalic bang noise a couple of times and then ran, some what of a concern and just wondered if
anyone has any idea what it could be, my initial guess is would it be the knock sensor? if it has one.

Cheers
Sean

[mjb]

possibly one of the glow plugs is defective? I know little about diesel but if you were chucking the stuff out the back of a cold cylinder which could be ignited by the exhaust heat from another cylinder, that would account for the bangs? And not firing one one cylinder would make it very rough until it got warmed up enough to run without the plug... maybe

[Welly]

The HDi is not really reliant on glow plugs for starting (especially in August) it's a tricky one but I suspect a sensor or sensor wiring is at fault (only a decent code read will help) or a dodgy injector perhaps. What's the history and mileage? ever use injector cleaner? maybe your engine mounts are really goosed?

Just found this, may help?.....http://www.ilexa.co.uk/forum/index.php/ ... 252.0.html

[mbell666]

Mine had similar that slowly got worse. Garage reckoned it was the big end, however i think (fairly certain) it was a duff injector. A good bit of injector cleaner did improve it, but didn't fix it slowly got worse a again.

I'd put in some good injector cleaner and see what happens.

[seanh01]

The HDi is not really reliant on glow plugs for starting (especially in August) it's a tricky one but I suspect a sensor or sensor wiring is at fault (only a decent code read will help) or a dodgy injector perhaps. What's the history and mileage? ever use injector cleaner? maybe your engine mounts are really goosed?

Just found this, may help?.....http://www.ilexa.co.uk/forum/index.php/ ... 252.0.html

Thanks for the link. The mileage is 92,635, I did forget to also mention that when running, the car will try to missfire or it feel's like that, and at times it power surges when tryinmg to accelerate.

I will get some injector cleaner, I personally don't like using that stuff.

I will try the basic stuff of glow plugs, as I that is a east start.

Does the vehcile have it's own diagnostic display reader?
But the dodgy injector/s may be a good pointer. Any good links for exchange Inj's?


Regards
Sean

[Welly]

I will try the basic stuff of glow plugs, as I that is a east start

I really wouldn't bother looking at the glow plugs, we never do. You're more likely to run into problems with one snapping off in the head, which is nice.

The HDi doesn't rely on glow plugs for starting - the fuel mist is already hot from being squeezed so much by the HP pump. Even when it was minus 8 deg C in January one morning my car fired up first turn and was just very slightly missy on one cylinder with a tiny bit of blue cold Diesel smoke which all settled down in seconds. I surmise that maybe only a couple of my glow plugs still actually work and have been in there since the factory but I've never had any trouble starting, ever.

[mjb]

I really wouldn't bother looking at the glow plugs, we never do. You're more likely to run into problems with one snapping off in the head, which is nice.

Think you can check glowplugs (they're just heating coils aren't they?) by just throwing a multimeter over the connectors and measuring the resistance...

[mbell666]

You should remove the feed wire first to do it properly. else you basically have 4 resistors in parallel, which makes telling if any of them are faulty a lot harder.