Idle and power troubles

I have a 2002 Jetta TDI with 59,600 miles.

I have an issue going on with my car that I need some help with. Before I spend time taking this to the dealer is there any quick solutions that I could try out first? I have a VAG-COM, timing belt tools, and other VW specific tools.

Symptoms:

-At idle the engine is fluctuating between 850-950RPM.

-My timing is within spec, but while looking at the timing graph for some reason it just goes blank for a second, and the engine makes a noticeable sound difference, almost like it is stalling. Then the timing graph comes back and repeats. (This seems to correlate with the fluctuations of the RPM at idle, although I can't see both graphs at the same time)

-The injection quantity (mg/stroke) was set around 6.5 but fluctuates from the high 5s to the low 7s.

-Power is down, car is running generally sluggish, and more than average smoke is apparent.

- I have recieved this fault code: "17656 - Injection Start Regulation: Control Deviation P1248 - 35-10 - - - Intermittent"

I have searched the forums and based on that here is what I have done:
-Replaced fuel filter (with CAT fuel filter)
-Checked the injector balance
-Cleaned all the electrical connections for the #3 injector, and the fuel pump.
-Checked MAP sensor, turbo is fine.
-Checked the MAF sensor, MAF is fine.
All these reported as working properly.

The only other possiblities I see are:
-Failed fuel pump
-Bad (G80?) needle sensor on injector #3
-Bad or needs screened cleaned on N108 sensor (Cold Start Injectior on pump)

Can anyone else suggest something I may be missing?

The problem you describe is exactly the problem we were having with a 1999 Golf (all stock). I thought there was an air leak at the fuel filter because of the occasional stumble. The car is now dead. About three months after the stubmle at idle started the car quit running. The fuse was blown leading to the pump, and it's our belief that the pump failed. Replacing the fuse does not effect anything so we think something in the pump shorted out, fried, and is now open.

A new pump is on the way, but we are reluctant to just swap it out thinking maybe something else in the vehicle caused the pump to fail.

I just noticed that my fuel temperature is reporting pretty high at the end of my daily commute. I drove home, and my friend in a similarly modded (and mechanically working) 2002 Golf TDI followed me. We VAG-COMed both our cars and my fuel read a temp of 232(221 is supposed to be the high point) and he read in the low 100s

Could all my problems be from just a bad 028 906 040 C temp sensor in the fuel injection pump?

HELP!!! Sorry everyone for not keeping your all up to date.... I didn't want to report on here while my car was in the shop, but suffice to say, they still haven't fixed the problem. Read on to see the note I dropped off with the dealer and the car this morning.

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Dear <advisor> and VW Techs,

It seems that the warrantee work that was done on my 2002 Jetta TDI including MAF and ECU replacement has solved the power drop-off at 3000RPMs that I was experiencing.

However, despite a timing adjustment to the vehicle, performed during this work, the timing in the vehicle is still deviating across a wide area and the fuel is reporting an extremely high temperature after moderate driving. This deviation can be heard by just listening to the car at idle, but a VAG reader shows the wild timing swing.

I drove from the dealership today after picking up the vehicle and moderate drive to my home about 5 miles away. I checked the timing graph on the vehicle and it reported "Fuel Temp too hot". Even with it off of the graph, a wild swing from "slightly retarded"

to "out of spec, too advanced" can be seen.


Then I let the motor cool down for about half and hour to get an actual reading. Still, at idle the timing graph would swing from "slightly retarded"

(Note: In this picture it reports that the engine isn't warm enough, even when it obviously is)

to "out of spec, too advanced"
.
I know that the timing is supposed to swing a little bit, but this looks like the sign of something bad. To give you an example of what normal TDI timing looks like (and similar to what mine used to always look like) see an example on page #6 (I inserted a standard timing graph like the one on ross-tech's TDI timing page)

Also, when the car reported such unusually high temperature readings I noticed that the cars engine cooling fans would kick on even after I turned off the engine and armed the alarm. Until these problems started I never even heard my fans kick on, even in the middle of an Arizona summer!

My 2 cents:
I'm guessing that this problem is either the fuel sender, injection pump, or both needs replaced.
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I dropped this packet of information off with the tech and he said that he would look at it when it was cold again... "becuase that's the only time you can check the timing is when it's cold" -VW Tech

Any advise any of you could give me at this point would be great! I'm at 59930 miles and my warrantee is up at 60,000, so I need to get this solved now, while it's on VW's dime!

It could be a injection pump going south. But, check to see if the three bolts are secure and tight on the injection pump pulley. If they are loose they could cause the timing to be retarded (though I don't think it cause the sway from retarded to too advanced like you say). Take the timing belt cover off and check the bolts.

Maybe it could be the cutoff solenoid on the pump. On the right side of the pump (toward driver's side) there is a wire leading to a clear plastic like bolt with a black washer inside. Sometimes these can come loose. You might reseat it and see if that helps.

-or-

it could be the fuel temp sensor. Do a search for it and you'll find a good tutorial on how to replace it. I've done it and it is very easy - if you are fairly mechanically inclined at all. Oh, here is the link:

http://forums.tdiclub.com/showflat.php?C...true#Post710979

I've heard of stealership service departments replacing entire injection pumps when a temp sensor is all that is needed. A pump replacement is a major job costing a lot in labor and basically requiring the timing belt to have to be redone also. A lot of BS to go through when it might be something so simple.

I've got the same performance mods you have. UpI or UpII (I've had both), advance timing a little to handle the longer injection window and in my car the timing appeared to jump around a little more on the VagCom timing graph(though not as much as your's) when I got it chipped and added bigger injectors. I keep mine in the upper portion of the graph (advanced).
Good luck.

Maybe it could be the cutoff solenoid on the pump. On the right side of the pump (toward driver's side) there is a wire leading to a clear plastic like bolt with a black washer inside. Sometimes these can come loose. You might reseat it and see if that helps.

Click to expand...

Are you talking about the N108 "Cold start injector" on the bottom of the pump with the one wire leading to it?

If not, could you post a picture or give more description as to where on the pump this bolt is? I don't have my car right now, so I can't even check it.

In the link I posted above, the solonoid I'm talking about is just to the right of the injector pump cap that is shown removed. It has a black thick wire shown going down over the the right top side of the pump (on that rusted area above and just to the left of the injector lines).

I'd vote for replacing the fuel temperature sensor (inside the top of the pump).

Check out this similar problem that I'm having with an out of warrantee car:
Cold Start Injector