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Engine Specific Info and Questions => TDI Engine -General Info => Topic started by: CrazyAndy on November 27, 2013, 07:56:42 am

Title: '98 Jetta misfire on cold start, lacking power when cold
Post by: CrazyAndy on November 27, 2013, 07:56:42 am
Hi all,

So I finally broke down and bought a modern car, a 1998 Jetta TDI.  Some history on the car:  Guy bought it w/ broken timing belt, bought rebuilt head, new injectors and glow plugs, and head gasket (I asked him about the notches, he said original HG was 2-notch, and that is what's on the car now).  It needs a new starter switch, and the PO before him, installed a remote button to get it started.  Also, for some reason, installed an Audi radio of comparable vintage.  Got it home 98 miles, and the very next morning started having a misfiring issue when starting cold (16 deg F).  It is repeatable, happening every time it starts after sitting for over 5-6 hours.  The first 2-3 starts it dies after stumbling for about 5 seconds, with blue/white smoke coming from the tailpipe.  After eventually getting it to start and idle, attempting to accelerate, either from a stand still or while moving, causes it to stumble and die again.  Once I let it run for a bit I am able to accelerate without it bogging down, but feels gutless until about 2400 rpm, with smoke front he tailpipe and sometimes feeling like the turbo is not spooling.

Checked so far:
-Pump cog and cam timing (OK)
-Pump internal timing w/ VAG-COM (over advanced, readjusted; problem still persists)
-Will install fuel filter today

What the hey could be causing this issue?  Could the PO have botched the head job (what I'm leaning towards)?  Could I have air getting into the pump (saw some bubbles from filter feed line; tightened clamp and diminished; hope internals aren't cavitated)?  Is there a sensor that can go bad, causing this to happen?  Ignition switch causing this, or K-wire feedback due to wrong radio?  I know this thing can run good, It's done it before.  Any ideas would be appreciated.

Thanks!
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: RabbitJockey on November 27, 2013, 08:03:40 am
more than likely, it is just air in the line.
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: CrazyAndy on November 27, 2013, 08:05:48 am
Or a seal in the pump letting it in, an unlikely but possible alternative.  I'll update after fuel filter install.  Are there any parts of the MK3 fuel system besides the pump inlet and return lines that like to leak?  Injector return lines?
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: theman53 on November 27, 2013, 09:00:24 am
I would guess the air in the pump would help starting. It maybe that the compression is down and after their head work they decided to get rid of it? I would pull the injectors once you have it hot and do a check. It won't hurt anything. Definitely fix your air.

Also as a side note when they did the head, did they used new nozzles in the injectors? If not I would say it is due.
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: libbydiesel on November 27, 2013, 09:28:24 am
So I finally broke down and bought a modern car, a 1998 Jetta TDI.

Ha ha, that's funny.  15 years old isn't exactly modern.  It's more than halfway to being an antique car!
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: theman53 on November 27, 2013, 09:31:11 am
So I finally broke down and bought a modern car, a 1998 Jetta TDI.

Ha ha, that's funny.  15 years old isn't exactly modern.  It's more than halfway to being an antique car!

funny but that is the way I see it too, anything newer than 90 seems pretty new to me
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: libbydiesel on November 27, 2013, 10:36:39 am
I remember when I was a kid, when my folk's car was 10 years old it was OLD.  Now my '02 Jetta wagon seems like a spaceship.
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: CrazyAndy on November 27, 2013, 12:46:29 pm
So I finally broke down and bought a modern car, a 1998 Jetta TDI.

Ha ha, that's funny.  15 years old isn't exactly modern.  It's more than halfway to being an antique car!

I DROVE an antique before this.  This has heat, power steering, a radiator, an ECM, A/C, and a radio that has more than 2 speakers.  It's modern (enough). :)
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: ORCoaster on November 27, 2013, 03:17:41 pm
Sounds like classic fuel filter plug creating a vacuum on run then when it sits air leaks back into pump causing start/run issues.

You could bottle feed it a while and see if that keeps it going or runs without the lag. 
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: CrazyAndy on November 27, 2013, 06:14:21 pm
Update on runing concern:

R and R fuel filter; concern persists.  Tested flow before and after fuel filter replacement; low flow in both tests.  R and R pressure line to ECM for fault '65535 - Internal Control Module Memory Error' as per http://www.myturbodiesel.com/1000q/a3b4/ecu-hose-chip-tdi-65535.htm (pretty nice 1000q); concern persists.  Visually inspected body fuel supply lines from filter to fuel pickup tube; no external damage present.  Next diagnosis step is bottle feed test as per ORCoaster recommendation, and in-tank fuel pickup flow test.
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: dieseljunkie69 on November 27, 2013, 06:25:18 pm
Next diagnosis step is bottle feed test as per ORCoaster recommendation, and in-tank fuel pickup flow test.

It has been ten minutes.

How did this workout?  ;D
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: 745 turbogreasel on November 27, 2013, 07:55:52 pm
Isn't that car supposed to have an electric lift pump?
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: CrazyAndy on November 27, 2013, 10:46:51 pm
Next diagnosis step is bottle feed test as per ORCoaster recommendation, and in-tank fuel pickup flow test.

It has been ten minutes.

How did this workout?  ;D

Ran out of time, temperature, and daylight.  I'll try Friday and/or Saturday, as tomorrow I have Thanksgiving family crap to do.

Isn't that car supposed to have an electric lift pump?

Nope, that's Mk4's, Mk3 and B3/4 TDIs still relied on the pump's own internal vacuum to draw fuel.  Sucks, don't it?  I could install a lift pump, but that is dependent on if the pickup filter is clogged or not obviously.

P.S.:  Anyone got a lead on new or good used Mk3 TDI Jetta fuel sender assemblies?  I have a bad feeling these things are NLA, as google searches on the part number just turn up Chinese copies.  No tank you.
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: 745 turbogreasel on November 28, 2013, 01:12:26 am
If you have a lift pump, I'd install it temporarily  as a fast way to do a leak check
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: CRSMP5 on November 28, 2013, 06:40:50 am
 ::)

bad glow harness... kicks on light.. one or 2 plugs dead.. so colder then others an dmisses makes smoke..
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: CrazyAndy on November 28, 2013, 10:59:38 pm
::)

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.
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: 745 turbogreasel on November 28, 2013, 11:33:58 pm
but if it was 10 year old heating oil it might
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: CRSMP5 on November 29, 2013, 09:36:35 am
sure i not gelling up?? whats temps like?

summer off road fuel not like winter fuel..
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: CrazyAndy on November 29, 2013, 02:56:08 pm
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! :)
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: rbremiller on November 30, 2013, 10:11:43 am

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 (http://www.vwdiesel.net/forum/index.php?topic=34130.0)
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: CrazyAndy on December 01, 2013, 05:00:36 pm
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.

(http://i1167.photobucket.com/albums/q639/CrazyAndy1/2013-11-30101046_zps04ec3975.jpg) (http://s1167.photobucket.com/user/CrazyAndy1/media/2013-11-30101046_zps04ec3975.jpg.html)

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.
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: bbob203 on December 01, 2013, 06:00:25 pm

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 (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.
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: CrazyAndy on December 24, 2013, 10:47:40 am
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.
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: TylerDurden on December 24, 2013, 01:06:41 pm
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.
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: Toby on January 03, 2014, 04:44:26 am
The air in the lines might be from a "biological" issue. How does it run at WOT?
Title: Re: '98 Jetta misfire on cold start, lacking power when cold
Post by: CrazyAndy on January 07, 2014, 07:57:20 am
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.