'98 Jetta misfire on cold start, lacking power when cold

[CrazyAndy]

bad glow harness... kicks on light.. one or 2 plugs dead.. so colder then others and misses makes smoke..

I'd like to say that's it, but even after the idle stabilizes, stepping on the pedal makes it miss; you can't accelerate hard, and the only way to get it to rev, even without load just siting in the parking lot, is by gradually getting on the pedal.  After it comes back down after unsuccessfully trying to get it to rev, the idle stumbles and the engine can cut off if it isn't warm enough.  I might be wrong, and yes the harness needs to be replaced, but I'm still going to test the fuel pickup for flow just to eliminate it as a culprit.  I didn't like the speed at which fuel was coming out the pre-filter line; took a pump before I saw fuel and even then was not flowing fast.  The PO filled it up with off-road diesel, not that it would create the problem.

[745 turbogreasel]

but if it was 10 year old heating oil it might

[CRSMP5]

sure i not gelling up?? whats temps like?

summer off road fuel not like winter fuel..

[CrazyAndy]

I did fill it up 40 miles from home; might have loosened gunk/gel in the tank.  For all I know it IS summer fuel, so either way there is some merit to checking the tank.

And I should be used to it, but damn glow plug harnesses are expensive.  A VW technician talking about overpriced parts; what a hypocrite I am!

[rbremiller]

And I should be used to it, but damn glow plug harnesses are expensive.  A VW technician talking about overpriced parts; what a hypocrite I am!

There's this option for the GP harness...
http://www.vwdiesel.net/forum/index.php?topic=34130.0

[CrazyAndy]

I like the idea, but I think I'll stick with the stock harness bus.  It was more a joke than anything.  I'm willing to put up with German prices as long as it means German quality.

In other news, I pulled the fuel pick-up out of the tank yesterday.  Looked kind of nasty so I back flushed it with some cleaner.



I also reached into the fuel supply line with a pick and checked the anti-return valve.  It felt kind of sticky like it had some sediment in it, so I back-flushed the line from the filter with some cleaner and the valve held open.  Didn't feel sticky anymore after that.  Also drained my tank to check for gel or sediment but found none.  But even after the first fill up, fuel dye is still very present in the fuel; it's going to take a few fill ups at near-empty to get the red out.

I got back home after driving around at 8:45 last night.  I start it up around 10:30 this morning, and from aside of a little air in the line (I think I'm going to have to get a new supply line) the car started up well, with only a light stumble probably as result of the air.  The bigger test will be letting it sit overnight tonight, as well as getting a new supply line later.  For now it seems to be behaving well.

[bbob203]

And I should be used to it, but damn glow plug harnesses are expensive.  A VW technician talking about overpriced parts; what a hypocrite I am!

There's this option for the GP harness...
http://www.vwdiesel.net/forum/index.php?topic=34130.0

did this on my 1z m today I wired in series though rather than individually.

[CrazyAndy]

Well the car is running better but still not good.  She bucks while at cruise load especially when cold, and still has a light miss when cold starting.  Gonna just go ahead and pimp the GP wiring like Vince did, and check the ECM internals to see if the internal vacuum pipe is good since the 'ECM internal malfunction' DTC is persisting.  I still haven't got the fuel supply line since I had to pay for Christmas crap, but I'll check if I still need it after doing the GP wiring and ECM internal vacuum line.  I'm also starting to wonder if one of those injectors' activation pressures might be off and shows it under light fuel load.

[TylerDurden]

It sounds like my TD which is still on a very retarded summer test timing. Warmup period is very smokey and misses on heavy pedal. Very poor fuel economy since the cold weather arrived too.

Low compression delays start of combustion, so it may need more advanced timing.

[Toby]

The air in the lines might be from a "biological" issue. How does it run at WOT?

[CrazyAndy]

Figured it out: injection quantity too low.  The new injectors caused the quantity to be 1.6-1.8 milligrams/stoke.  I adjusted via VAS-PC and hammer mod until it reached 4.0-4.2 mg/str.  She started up fine this morning at 4 deg. F, aside from one stumble and one only which I attribute to it being so cold and the fact that I still haven't fixed the GP wiring.  But there's no more bucking when cold, no more slight skipping/bucking at cruise, no ever-so-slight nailing of one of the one of the injectors.  Only drawback is that now there's a slight increase in pedal effort when cold, but as long as WOT power and fuel mileage stay constant then it's fine.  If not then I'll adjust it closer to 3.0-3.5 mg/str.  Glad to have finally taken care of that.