CEL Light and blinking glow plug with Rough Idle

MDD

Member
Joined
Jun 13, 2004
TDI
2001, Jetta TDI
2001 TDI Jetta. To start dealer tells me the only code they pick up from the CEL is a bad glow plug. So I'm at 60k miles and out of warranty with no maintenance costs since brand new, why not, I buy a new set of glow plugs from tdiparts.com and install them. Clear CEL, comes right back within 2 minutes of running idle.

Next I buy a brand new Glow Plug Harness and Glow Plug relay. Reset CEL and still no change, but now I have a rough idle even after driving it for a while. It comes and goes, it could idle great for 5 minutes then rumble and shake at a stop light like its going to die, but runs great on highway. I then replace the MAF with the Piersburg version along with a K and N filter. 3 weeks later of trying to ignore the engine rumble and CEL (I only drive 4 miles to and from work) the Glow Plug light begins to blink. Some days it comes on and some days it doesnt, and it usually doesnt come on until I am out of the driveway and down the street. So I put back in the original plugs and harness with no change, still the only code being thrown is bad glow plug (New Plugs, New glow Plug Harness, New MAF, New Glow Plug Relay, New Fuel Filter, New Air Filter). Only thing left I can find to try is to put back the original code currently upgraded to Upsolute, but that code has run great for 3 years.

Any suggestions?
 

Toronto_Vento

Top Post Dawg
Joined
Nov 7, 2002
Location
Richmond Hill, ON
TDI
01 Baltic Green Bora
Last time I had a CEL and flashing glowplug light, I had an N109 code. It ended up being due to biodiesel with something in there that the fuel pump didn't like. It's a little hard to say without taking a look at the car. If you only drive 4 miles to and from work, there is a decent chance that you have some clogging in the intake. This COULD lead to a rougher idle, as you would be choking the engine for air.

Then again...a blinking glowplug light could also indicate that one of your rear brake bulbs is burnt out, or that your brake switch is shot (if it is the brake switch, VW should replace it for free even though you are out of warrenty...there is a service buletin about it).
 

MDD

Member
Joined
Jun 13, 2004
TDI
2001, Jetta TDI
I'm in Dallas Texas. 80 degrees here this week so I know the plugs arent being used for anything.

I have used Biodesiel in the past, and even tried making my own. But I havent used that stuff in over a year. Especially since I dont drive far enough to make it worth anything.

As far as recalls the only one I received is a window machenical issue thing.
 

weedeater

Top Post Dawg
Joined
Mar 17, 2001
Location
Reston, VA
TDI
Jetta, 2001, Baltic Green
Brake switch will cause the light to blink.

If it were truly GPs, I would just ignore it. But a rough idle is something else.
 

Wingnut

Top Post Dawg
Joined
Oct 10, 2002
Location
Toronto & Whitby
TDI
Silver 2003 Jetta Wagon
Yes, the blinking glow plug light is a signal that there is a malfunction in the brake light system. But since his blinking GP light is accompanied by a rough idle, I would bet it has something to do with the injection pump. One of the codes associated to a flashing GP light deals with the injection quantity. I don't know the exact code right now, but what you need to do is get the car scanned. Lots of TDIClub members in Texas. I'm sure there are a lot of Vag-coms too.
 

Magnulus

Veteran Member
Joined
Feb 20, 2005
TDI
2003 Jetta Wagon white
I've had the exact same thing happen. I think its something in the fuel. How is the fuel filter? Are you using any additives? Redline or Power Service in a large dose (one ounce per 1-2 gallons) seems to cause a CEL and engine missing (irregular, rough), along with the flashing glowplug light. Conversely, if you aren't using additives, try using a small amount of Redline Diesel Fuel Catalyst or Redline 85 Plus and see if that doesn't improve it (maybe one ounce per 4-8 gallons).

One thing I can suggest- if you see the CEL + glowplug and the engine is missing- turn off the road as soon as possible. The engine might die. And never drive off if you start up the car and the warning lights are going and the engine is missing- again, the car is probably going to die at some point. I had this happen a few weeks ago- car started with a CEL + glowplug and rough idle. I just pulled over into a parking lot and parked it, then the engine died. I waited a while, then drove off and no CEL light. Maybe the engine was "passing" something it didn't agree with.

I've been draining my fuel filter occasionally and testing for water (red food coloring dye in the diesel works). So far I haven't found much, if any.

You might also want to get somebody with a VAG-COM and get them to test the timing of the engine and the fuel injection at idle. I've been meaning to do this too, but I haven't gotten around to it. I would take it to the dealer, but they will probably try a thousand other things first, all of which cost $$$$.
 

runonbeer

Maintenance EnthusiastVendor
Joined
Apr 15, 2002
Location
Austin, TX/Chapel Hill, NC
TDI
'00 Golf 02M, '10 Golf 02E, '02 UTE 02M
MDD, I will be in dallas this weekend. I'll bring my VAG COM if I can convice my ride to swing all the way south before the long journey north (laptop is at the shop)
my cell is 210 862 7502. call me and I'll let you know if I can help you out.
 

MDD

Member
Joined
Jun 13, 2004
TDI
2001, Jetta TDI
Thanks for the response. Do I need a document of some kind to get the Brake switch replaced?

Have some new information to add. First I havent used any additives in a long time. Almost 2 years ago I used STP diesel treatement for 10 full tanks in a row, each bottle said it treated 8-10 gallons and on the bottle it recommended to use every fillup. I disconnected the fuel filter (less than 1,000 mile on it) and dumped it into a bucket. I found at the top of the filter a few bits of what look like little hairballs or snot coming into the filter from the Injector pump return. I dumped it out refilled it and took it up on the highway run full throttle through the gears for about 5 miles and afterward I have a lot more power, its alot easier to take off from a stop, etc. But of course the Blinking and rough idle is still there, idle id just barely noticable now, but when I am in gear and giving it gas its smooth as new.

Another thing, this GP blinking and CEL have been going on for more than 6 months and has never caused it to die on me and the only noticable performance has been about 2-3 mpg less than normal. Its not really causing problems, in fact its allowed me to continue using the stock clutch for a bit longer until I can afford one that can handle the upgrades. The major issue I think is that I need to get rid of the CEL to get it inspected. They look for that as a sign of emissions problems, but they dont hook it up to anything, they just check blinkers, lights, and look for CEL.

Also I upgraded to .205 injectors about a year ago. Ran fine for 6 months after the install. Sent my old injectors back for the $400 core charge, otherwise I would drop the old ones in for a test.

The upgrades were installed over a year ago and I never had any problems after the upgrade. The chip tunning was 3 years ago, and the K&N filter was recently recharged.
Total changes so far: .205 injectors, Upsolute chip upgrade, K&N filter, New fuel filter, new plugs, new plug harness, new plug relay, I have a new 2" downpipe kit I need to install (maybe that will help it breath better?).

I am now looking into purchasing a VAG COM to help me keep things in check, but would Greatly appreciate any help someone near me can provide. I am in North Dallas Richardson area, if anyone might be insterested in helping me with the codes please call my cell and we can meet wherever (214-564-5562).
 
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