My engine misses when cold

[vwmike]

So, like the title says, my engine misses when cold but gets better as it warms up. It also tends to smoke more when cold and the stumbling gets worse at certain throttle positions. I've never owned a diesel before so I'm still learning on this a bit, but I can only assume one of two things - fuel or compression. Being as though it runs fine otherwise with no oil consumption to speak of I tend to think it's a fuel issue. It's only getting about 39mpg so I tend to think it's just getting too much fuel and it can't atomize properly when it's cold.

What do you guys think?

[QuickTD]

Your timing sounds like it is slightly retarded.  Does pulling the cold start advance help?

[fspGTD]

Sounds like a textbook case of bad glowplugs to me.  :wink:

First test that voltage is getting to them when it should be.  This is easy to do and rules out a bunch of electrical problems like the glow plug relay, glow plug firewall-mounted fuse, etc.

If you're getting voltage, might want to buy a set of them (they are not really very cheap though!) and then remove the buss bar to test each individually, either replacing just the bad ones or alternatively, replace all of them together.  I'd recommend just trying to keep all 4 plugs having the same brand & correct part number for the application, if possible.

A couple of the plugs are really tricky to get at.  You can either use magnets-on-a-stick and wrenches, etc plus a bunch of patience and with a lot of dexterity and skinny long digits, you may be able to access them while leaving the fuel hardlines in tact.  Otherwise, consider removing your fuel injector hard lines to make access easier.

If you do remove the fuel hardlines, take every precaution to prevent dirt or dust from getting into the injector ports - it only takes the smallest particle to screw up an injector permanently!  IE: clean the fuel hardline unions by spraying cleaning solvent around before loosening them, also cover or cap the open fuel union ports once they are exposed, etc.

Once you have the buss bar removed, you can test each glow plug individually while it is still screwed into the block by measuring it's resistance.  A low resistance (say, around .5-3 ohms or so) means it's good, while a very high resistance (open or near infinite) means the plug is bad and needs to be changed.  My experience with running these engines in northwest climate is that they can be started quite easily with 1 bad plug but get very hard starting in the cold with 2 or more bad.

The bad plugs cause it to run very rough when cold due to the misfiring cylinders, but this goes away as the engine warms up at which point it starts running "on all four" and much more nicely.

[vwmike]

My cold start advance isn't currently working. I guess the cable is toast or something. That never seemed to make much difference in my friends truck. I know the glow plugs are getting power and they have been changed sometime in the last few years...but I suppose it's possible they could be bad again. I've had some previous experience with glow plugs and the racheting wrench is your best friend on that one. But, before long I'll have everything apart since I'm changing the passenger mount, timing belt, swapping on the TD injector pump, and putting in the TD injectors. I can check and replace the glow plugs then if I find any that are bad.

I changed the clutch on it about a month ago and when I put it back together all the wires had come off of the senders on the water neck. When I put them back on I noticed the glow plugs were sensetive to coolant temp - something I had no idea of before. It seems like they don't come on when they should. Like after I drive a short distance and shut it off, I have to crank it quite a bit more to get it to start. Normally when the glow plugs are let warm up I just barely have to touch the key to get the engine to turn over.....except when it's really cold like you said, then I have to try a couple of times before it starts.

[fatmobile]

my engine misses when cold but gets better as it warms up.

 sounds exactly like mine ... when I don't pull the cold start lever.
 Fix your cold start cable .... or go out in the engine compartment and move it by hand.

[vwmike]

I got the cold start knob moving and stuff....it doesn't seem to be any different.

[fspGTD]

VWMike, have you checked out your glowplugs yet?

If you want to be able to troubleshoot this yourself, download the protraining manual from this thread:
http://www.vwdiesel.net/phpBB/viewtopic.php?t=321&start=0&postdays=0&postorder=asc&highlight=protraining

And check out the troubleshooting guide on cold starting problems that starts at pg. 24.

HTH...  Good luck.

[fspGTD]

I've got a sort of related question on this topic... has anyone found that different valve clearances cause a cold starting problem before?  In theory, it's possible that having too thin of intake valve clearance delays closing of the intake valve and causes a loss of compression build-up at slow RPMs.  I'm just wondering if practically speaking, if too tight of intake valve clearances can actually cause noticeable harder cold starting?

[vwmike]

VWMike, have you checked out your glowplugs yet?

If you want to be able to troubleshoot this yourself, download the protraining manual from this thread:
http://www.vwdiesel.net/phpBB/viewtopic.php?t=321&start=0&postdays=0&postorder=asc&highlight=protraining

And check out the troubleshooting guide on cold starting problems that starts at pg. 24.

HTH...  Good luck.

That was a lot of scanning they did for that manual. I haven't gotten around to checking the glow plugs yet. I just bought a dial indicator with the adapter and stuff so i can set the pump timing. So, sometime this month I'll be replacing the passenger motor mount, putting on the TD injection pump, and the TD injectors. While I have the pump off I'll check the glow plugs and replace any if necessary. I hate trying to get to them with the pump in the way. If the problem still persists after that then I guess I'll check valve clearance and such. I still need to buy the shim pliers and the valve depressor....I have always adjusted the valves without the tools in the past, but I guess I should just get them.

[dieselpower]

hey,
my car has that same problem. and i'm only talkin about like -5C when it happens.

all 4 glowplugs are good, replaced the injectors 2 days ago so they're good. timing is a little advanced 1.04 and my timing advance works properly.
can anybody help.

does anybody know if what FSPgtd was right about the valves being tight and losing compression. because that would make sence to me. cuz last winter it was good. but now with all the hard driving and drag racing i did during the summer my valves might have tightened up. i DO need a new battery tho as mine barely has enough juice left to crank over the motor anymore but that doesnt affect anything once its started.
thanks for the help

Mark

[vwmike]

Ya know, I've noticed lately a small miss at lower rpm's on the freeway. I'm wondering if my injectors are just dirty or something.  :?: