need help car stalled and only restarted after holding to the floor

[jrb]

I was idling in traffic with the air on (90+ 80% humidity) and noticed it running rough. The idle never really moves from around 900 but it was dropping down to below 800 then back up. I gave it fuel to try and see it was fowling out but it died as soon as I touched the pedal. It would not start and only started after holding it to the floor and cranking it for about 10 seconds then billows out a big black cloud, chugs like it is running on 2 cyclinders then clears up and runs fine. Now it appears fine but I dont have my laptop for my vag-com to check codes. Any help from anyone who has had this happen would be very much appreciated. EGT was under 600 and boost appears fine. I did have about 28,000 miles on the fuel filter and changed that when I got home.

John
1998 jetta tdi ahu
chipped.

 

[jrb]

addionally no error codes were in the computer and timing looked exactly where I left it last time I set it.

 

[fastvicar]

Clean your intake manifold. While my B4 didn't falter at idle, it would try to stall after romping on it in 1st gear, then require your same cranking routine. No problems lately.

 

[Lug_Nut]

It would not start and only started after holding it to the floor and cranking it for about 10 seconds...

Pressing the accelerator while cranking does little more than nothing. The cranking rpm is less than idle rpm. The ECU is already adding more fuel to bring the low speed up. Your pedal request to the ECU is merely a duplication. The engine would have coughed and bucked to life in the same time with or without pedal application.
Once running at normal 900 rpm, then pedal application is effective.
Not that that helps you with your issue, but just don't think that tromping the accelerator will aid starting in anyway, or that neglecting to "set the choke" or "using the accelerator jets to prime the intake" will cause hard starting..

 

[jrb]

Thanks, I forget that it is more of a fly by wire with the ecu. Well I pulled the intake and it looks just like it did after I cleaned it last year. I have modified egr system to not open as often and use an oil catch tank in between the valve cover breather and the intake. I drained water and dirt out of my fuel filter. I had just gotten back from vacation a few days earlier and stopped at a very out of the way station for fuel and I probably got old fuel. I did not follow my own rule of not fueling where the the big rigs do. I replaced the fuel filter yesterday just to be safe.

 

[fastvicar]

Pressing the accelerator while cranking does little more than nothing. The cranking rpm is less than idle rpm. The ECU is already adding more fuel to bring the low speed up. Your pedal request to the ECU is merely a duplication. The engine would have coughed and bucked to life in the same time with or without pedal application.
Once running at normal 900 rpm, then pedal application is effective.
Not that that helps you with your issue, but just don't think that tromping the accelerator will aid starting in anyway, or that neglecting to "set the choke" or "using the accelerator jets to prime the intake" will cause hard starting..

That was my theory, too. But holding the accelerator down while cranking does make a difference. It shouldn't, but it does.

 

[Lug_Nut]

That was my theory, too. But holding the accelerator down while cranking does make a difference. It shouldn't, but it does.

Then it's high time I try it for myself with VAG COM connected to see the changes to the pump created by the "WOT" signal from the drive-by-wire accelerator.

 

[fastvicar]

I discovered this after changing all four of the injectors & fuel filter on my sister's B4V in one operation. (I never should have done it, but it was about 1AM and I wasn't thinking clearly) The only way it would even begin to sputter was by holding the pedal down. As soon as I would release it the car gave up all hope of starting. Who knew?

 

[RoundHouse]

Use a zip tie and wire the anti shudder valve open.

And change the fuel filter if that doesnt fix it.

 

[Lug_Nut]

...wire the anti shudder valve open.

Not present in the A3/B4 TDI.

 

[RoundHouse]

Not present in the A3/B4 TDI.

Oh,
I noticed in his sig it was a '98, and our '98 Beetle has one, and did the same thing till I wired it open & yanked the vac hose.

 

[rdkern]

98 Jetta was an a3 - your 98NB is one of the first A4's in the US.