Super quick cutoff/power loss/miss

Hi, I have a 1998 VW Jetta TDI. I've had the car for about 10 years and I give it regular maintenance. Now has about 310,000 miles on it. A couple of months ago, I was cruising down the freeway and suddenly had a loss of power that almost felt like a miss. Glow plug light illuminated momentarily. Car recovered on its own with no codes thrown. It happened so fast that if I had blinked, I would have missed it. I felt it though. Since then, its has done it intermittently a handful of times. The only constant parameter is cruising at higher speeds. So far, I've checked for IP chaffed wires and codes but that's about it. With this car, usually when something start happening like this, it's a sign that something's about go out. But what? All ideas welcome!

Did you scan for codes with a VW-specific scanner like VCDS or a generic OBD2 unit?

I ask because there are a ton of VW-specific codes that a generic scanner will not be able to pull... and given that the glowplug came on it's strange there are no codes logged.

That said... this sounds like a classic intermittent Relay 109 hiccup, and there would be no codes if this was the case. What colour Relay 109 is in your car, and has it ever been replaced?

So I should clarify, it was the "wait to start" light that blinked on then off. I scanned the car with my VCDS. Where is the 109 relay?

Vince Waldon said:

Did you scan for codes with a VW-specific scanner like VCDS or a generic OBD2 unit?
I ask because there are a ton of VW-specific codes that a generic scanner will not be able to pull... and given that the glowplug came on it's strange there are no codes logged.
That said... this sounds like a classic intermittent Relay 109 hiccup, and there would be no codes if this was the case. What colour Relay 109 is in your car, and has it ever been replaced?

Click to expand...

I changed a relay quite a few years ago when I was trying to resolve some glow plug issues but I don't remember which one it was. It's been so long since I've been in the relay box that I've forgotten where it was. I remember now though. I'll pop it open and take a look in a little bit.

If you search on "Relay 109" here you should find some good threads with pictures on where it is, etc. In particular there's a specific colour relay to look out for.

It's not related to the glow plugs per se... so it may not be the one you replaced previously.

It provides power to the ECU... and so when it hiccups the engine stalls *and* the glow plug / wait to start light will come on briefly as the ECU powers up again.

Very common intermittent failure for older cars, particularly if they still have the original 109.

Vince Waldon said:

Did you scan for codes with a VW-specific scanner like VCDS or a generic OBD2 unit?
I ask because there are a ton of VW-specific codes that a generic scanner will not be able to pull... and given that the glowplug came on it's strange there are no codes logged.
That said... this sounds like a classic intermittent Relay 109 hiccup, and there would be no codes if this was the case. What colour Relay 109 is in your car, and has it ever been replaced?

Click to expand...

Color of the relay is black with white lettering. I personally have never changed it.

Aha. Black is the colour of the original 109 that like to go south intermittently.

The upgraded replacement would be grey:

http://forums.tdiclub.com/showthread.php?t=31070

Vince Waldon said:

Aha. Black is the colour of the original 109 that like to go south intermittently.
The upgraded replacement would be grey:
http://forums.tdiclub.com/showthread.php?t=31070

Click to expand...

I got a replacement today and it's gray. Thanks for the help. Hopefully that resolves my problem. Sounds like it will though.

Well, intermittent problems are always the worst...all you can sometimes do is guess.

Fingers crossed for ya!