E300D Rough for 60-90 seconds cold start
 

So cold weather is setting in and I've noticed on those mornings, I'm getting a rough start for the first minute or so w/my '99 E300D, after which it smooths out nicely. Now last winter, I lost a glow plug and replaced the whole set. So I'm surprised to be back here again, but am not getting a CEL.

FWIW, last winter replacing the glow plug set started a whole ugly cascade of costly events, because two of them were seized in the head. Required machine shop visits, car rentals... over $2k in repairs, ugh. So I can't imagine they would be seized, but as you might imagine... I'm hesitant to go there again.

Probably a glow plug (again?). Possibly injector? I'm guessing one of them (gp's) may not be well seated. Totally guessing though.

Thanks for any thoughts on this!

I don't know if the "newer" cars like your '99 are smarter than the old ones but it's possible to have a bad glow plug that doesn't cause the glow plug light to not illuminate (or stay illuminated after starting -- there are a number of error modes). Whether that would / would not cause a CEL I do not know. It's easy to check the glow plugs with an ohmmeter by pulling the six-pin plug off of the glow relay and checking each pin to ground. Should be no more than 1 ohm each.

It is also possible to have a bad glow relay; perhaps the afterglow function has ceased to work.

All of this assumes you're starting on diesel and warming up the engine before switching to WVO.

Jeremy

Agree with Jeremy to test all glow plugs and the 12v supply to the relay with a multi-meter, this should rule out wires too if they test all good- you can also open up the relay with a screwdriver and visually inspect/test with the cover off to make sure it's operating ok. My previous car's relay started to play up at about 195k.

You may also have a small air leak into the system, again my old car had this and ran rough in winter at start up 'till it bled out...

Both good suggestions from Jeremy and Chazola.

60-90 seconds is quite long for a lumpy start. Can you time how long it takes to fire on all six?

I have a rough start about 50% of cold starts in winter but at most it would be 20 seconds. I'll do some diagnosis but not until I have another reason to take off the inlet manifold.

I had a similar rough start at 50 degrees F or colder. I was doing some other work and had my injectors removed and noticed that one GP looked shorter than the rest when looking through the injector hole. It wasn't inserted all the way. I removed it and cleaned the carbon out and installed a new plug and now it starts better than it has in the 2 years that I have owned the car.

What a great picture of the plug glowing inside the cylinder!

Thanks folks -- if weather permits I will try and pull the manifold this weekend and put a volt/ohm meter on the GP's. We've had weather up this way and I'm without a garage at the current time.

Would have replied sooner, but for some reason I didn't get the email notification.

Thanks again!!

Howdy, neighbor! Our 1998 car (185kmiles) has starting doing the same since the weather turned cold. It's only running on 5 cylinders when it first lites off in the morning. Car runs great otherwise.

All GPs were replaced around 125k miles...maybe it's time to do it again :(

I had mine replaced last January with much blood, sweat and some tears because of the machine shop work involved. I'm guessing one of them may not be seated as well as it should be. Boo!

Where are you in N/E? It's pretty chilly here for Novembrrrrr.

-Chuck

I'm two towns over from you.

Did you used to have a VW TDI, by an chance ?

It's true. I had a TDI Beetle at one point. Actually I've owned two of them! Have we met?

Yes, we used to swap stories over on TDIClub ;)

I had similar issues and it was traced to a engine coolant temperature sensor that is located underneath the intake manifold. Good luck.

That's a great suggestion, thanks!!