Lumpy / hesitant cold start?

[yashicamat]

When I cold start my 110tdi (110k miles on the clock) it takes a few seconds of cranking and then runs very rough for a second or two with a belch of grey smoke before the revs pick up and it idles smoothly. After then it's the usual VAG diesel slightly rattly until it warms through a bit, then sweet as a nut. Hot starts are flawless.

Any thoughts folks? I'm thinking glowplugs perhaps . . . although they still seem to respond quickly on a cold start (on for a few seconds then switch out).

Ta.

[mbames]

glow plugs, coolant temperature sensor, timing off a bit?

My 110TDi is up to 160k now :-)

[yashicamat]

glow plugs, coolant temperature sensor, timing off a bit?

My 110TDi is up to 160k now :-)

I wouldn't have thought the timing would be the cause as surely this would be an issue all the time? Does the coolant temp sensor (I assume it's the fairly obvious sensor on near the top of the engine on the main coolant pipe?) have a resistance it should show when working OK?

Ta.

[yashicamat]

Update: Just tested the resistance of all 4 glowplugs . . . . the one furthest to the right (plug 1? It's the first on the harness anyway . . .) is showing a resistance of at least 300 ohms, compared to 0.6 ohms (or thereabouts) on the other three. I think I have found my culprit . . . .

[mbames]

Sounds like you might have found your problem.

The coolant sensor, yep you have probably found it, has 4 contacts - which I believe are 2 for the ECU and for the guage on the dash.... As yet I have not had to change any of my glow plugs, although some mornings my garage gets filled with a bit more smoke than normal

[KenONeill]

Mine's a bit the same, but it's started ok even at -12C. Just let it idle for a few seconds until all 4 cylinders join in the game.

[Stuart_J]

158000 on ours, same problem. Tried Glow plugs & no difference. 99% certain its not injectors. The colder it is the worse it is, once the car has warmed up its fine for the rest of the day. Ours started over a year ago. Im assuming drippy injectors would give the problem to an extent in hot weather, ours is smoke free on a hot day

Latest theory is the oil pump getting tired, top end of the cars hydraulic so it struggles initially to get the hydraulic tappets working. Our cars ben on variable servicing & the heavier oil is considered to be part of the problem working the pump too hard. The Garage who now service mind have had the same on a high mileage Audi. Are your cars on variable ??

Edited 22 February, 2010 by Stuart_J

[yashicamat]

Mine is on variable, but I have another pending issue directly relating to the glowplug install . . .

[trundlenut]

I had cold starting problems and it turned out to be the fuel pump timing. There was no issue with starting when warm. When I had the car checked with vagcom the timing was so far out it was almost off the graph.

My first thought was glow plugs but changing them didn't really help. I also had a problem with the 109 relay at the same time just to confuse matters.

[KenONeill]

If your fuel timing is out, it will affect the consumption as well (and not in a good way). I found this out when the cambelt was changed, and the garage checked and adjusted the fuel timing as part of the job!

[yashicamat]

Right, well cold start this morning with the replaced glowplug . . . still hesitant, but a lot better than it was. Still something not quite right though. I might just live with it now though as it's not as bad . . .

The mention of a possible failing oil pump is a bit concerning though as that could kill the turbo without much warning.

[trundlenut]

Get someone with vagcom to check the fuel pump timing - you need the full version though, not the shareware version.

[vRSLen]

Rob, the oil pressure warning light would be lit if pressure was an issue.....

[yashicamat]

Rob, the oil pressure warning light would be lit if pressure was an issue.....

Hi Len,

Yeah that's what I would have originally thought . . . it was this thread that made me think otherwise.

[Stuart_J]

Rob, the oil pressure warning light would be lit if pressure was an issue.....

I was told the same, aparently its just the first few seconds of running & that the pump would be fine to carry on using the car. The chap who serviced it has years of VAG experience & is pedantic when it matters so I tend to trust his view. He also knows how hard I drive cars so any potential problem & he would advise a change. The plan was to change the pump at the next service but it looks like the car will be sold before then. The new owner is aware of the problem & it dosent seem to worry him.

[reesky]

I was told the same, aparently its just the first few seconds of running & that the pump would be fine to carry on using the car. The chap who serviced it has years of VAG experience & is pedantic when it matters so I tend to trust his view. He also knows how hard I drive cars so any potential problem & he would advise a change. The plan was to change the pump at the next service but it looks like the car will be sold before then. The new owner is aware of the problem & it dosent seem to worry him.

Any other ideas folks? I have exactly the same symptoms. 110tdi, 83k. .Fine when warm. Glow-plugs changed. No faults on VAG-COM.

Battery, perhaps? Seems to crank quite slowly when cold and then TONNES of white / grey smoke.

[Tom_vRS]

I really do think its an injector problem. Replacements can be had on exchange for £38 each, or they might respond well to ultrasonic cleaning.

[cheezemonkhai]

Ultrasonic clean and possibly renozzel the injectors or get new ones fitted (They are not expensive like the PD ones).

FWIW the injectors tend to lose their spray pattern somewhere around the 80k mark, often spraying the fuel onto the bores and not misting it properly either.

That means the initial combustion is a lot smokier and more problematic until a few cycles have got the engine up to speed.

The oil pump could be an option, but to be honest, it might just be that the strainer is full of crud.

If you want to get it checked out then rather than just draining the car at the next service, have the sump dropped and the oil pump checked and either cleaned or replaced.

[rwbaldwin]

Sounds like the case pressure relief valve may have popped apart. This affects the pump timing.

see http://forums.tdiclub.com/showthread.php?t=238872&highlight=tdi+case+pressure+relief+valve

The next most likely problem would be the basic pump timing. Has the timing belt been replaced recently? Needs to be checked using VCDS.

It could be the injectors. They actually start to lose performance as early as 60k, however, I wouldn't expect them to be so bad until about 150k. The engine will run very rough if injector 3 is performing poorly as it includes the needle lift sensor

HTH

[reesky]

I've found that cycling the ignition seems to help things - although the garage claim to have changed the glow-plugs.

Could that suggest anything further? STicking relay, perhaps?

[yashicamat]

Just an update: took this video this morning. About -2 deg C so fairly chilly. I gave it a tiny blip of throttle when it caught.

My link

[Tom_vRS]

Bet that leather is nice and cold through that shirt!

Get the pump timing checked, re-check the glow plug resistance and wiring. If neither of those come to fruition, either stick some new injectors in (well, recon ones anyway), or live with it.

[reesky]

yashicamat - yours is a lot better than mine!

Mine's in with the garage today for timing check and coolant sensor replacement - will report back tomorrow or later.

[sparky93]

mine was lot worse, its in having hg done, but still think its cracked.

[karlbar2k]

I know its not the same engine but I cleaned the egr valve on the wifes passat 130Tdi (I also changed the air filter as it was quite cr4ppy) and the cold start and idle is much improved, now it fires up and very quickly settles at 800rpm and no where near as smokey. It has recently been changed to the green top sensor as well, I bought one ready to change on the Octy but hers went first