Sick Evil Beetle...

Me, my wife and my son all have miserable colds. Yuck! Our house sounds like the TB ward in Bankok General Hospital!

Unfortunately, the Evil Beetle must have caught the same virus. I drove back home on the freeway this evening through a heavy rain. Temperature about 40 to 45 degrees F. The EB is not used to rain, since it lives in a desert. I've driven in rain before, but not very often and probably not as heavy as this.

After I exited the freeway near my home I noticed that the car was "surging" (there's that word again!) almost like the fuel was shut off. In fact, it reminded me of the times my old 240Z would vapor lock on hot days!

1/4 tank of fuel left, and no problems before tonight. I decided to fill the tank with fresh diesel from the Flying J truck stop. No difference. I got home and gave the car a dose of Power Services Arctic Express, some Cetane Boost and a WHOLE BOTTLE of DieselMotive injector cleaner. I drove around for a while to let the additives circulate. No difference!

The car idles just fine. Above 2000 rpms it runs just fine. Below 2000 rpms it runs just fine if I give it plenty of "gas." But with VERY light throttle, below 2000 rpms, the car bucks, misses and "surges." If I step harder on the pedal everything is suddenly just fine.

Any ideas? I think a sensor or relay has gotten wet in the rain and is causing problems.

-mickey

Mickey, maybe there is water in the tank. There was a ton of rain tonight. In fact my I found some water(dorps)comming in my door as the wind would come across the wipper and door seal. Also, just was thinking about Flying J, have you had any problems. I have two clents that have trucking companys that said, "don't use there stuff" that it was bad," to use Amaco." I fill up and the T/A when I over in that area. If you fill that the TDI runs good on Flying J, I would like to know. That way I will use it and save some.
Thanks



[This message has been edited by karmann ghia (edited February 21, 2000).]

The Flying J fuel down here in Central Florida has provided me with good service in the bulk of my last years driving. Mix in a bit of Citgo, Exxon and whatever I could find during trips and I've experienced NO fuel troubles. Water? C'mon down here this summer and get a taste of the local thunderstorms. Of course our friends in California could give some horror stories this week. Good luck and keep the TDI above the water line.

I would check the potentiometer on the accelerator pedal. Make sure dirt, dust, or carpet fuzz buildup isn't causing a poor reading of the pedal position.

Brian, 97 Passat TDI

It sounds like the problem that Alberto_gago had, (which we never found the answer to. Alberto, are you out there?), without the smoke or the fellow from Norway (which was a rotted vacuum sense line).

Now my car is a 2000 so it might be different than yours, but I stupidly didn't assemble the intake tract when I was looking for an existing penetration through the firewall. Anyway, this duct was the section right after the maf. I didn't notice it was missing because of my conservative driving style until it came to climbing hills. So.....maybe it's not the maf sensor.

Karmann: Is "no where" anywhere near Stansbury Park? By the way, the tankful of fuel was bought at a Sinclair station in Salt Lake. I had used 3/4 of it without any problems. My car seems to like Sinclair the best, but I've never had any driveability problems with the Flying J stuff. That's a VERY busy truck stop, so their fuel should at least be pretty fresh.

Lately I've noticed that the idle speed kind of "see-saws" a little bit when I first start the car in the morning. Almost like the engine forgets it's supposed to be running, and then catches itself. It does this in a rhythmic manner for several seconds, then everything is fine. This morning, though, the problem was VERY severe, and I had a hard time driving while the engine was cold because it was bucking and kicking so much. However, lots of throttle "cures" the problem and the engine seems to run smoothly. Freeway cruising is as smooth as silk. I also noticed that the car produces an unusually thick cloud of black soot when I take off from a stoplight.

This has to be a sensor problem. A fuel starvation or water problem would become MORE severe as demand for fuel increases, not less so. (Right?) I'll check the operation of the Throttle Position Sensor with my OBD II software, but I don't think that rheostat is the problem because this happens at idle, when there is zero input from the TPS. (Idles just fine when the engine is warm, though, which also tends to indicate that the TPS is not the culprit.)

I can look at the MAF sensor readings in real time, so I'll check that. The MAP/IAT sensor is probably not at fault. Needle lift sensor is a possibility. Fuel cutoff valve? Doubtful, since that would cause problems at any engine speed. Maybe a bad relay somewhere.

-mickey

[This message has been edited by mickey (edited February 22, 2000).]

mickey, it sounds like the same thing that happens to me when I adjust the 'S' potentiometer on my Hopa too much. I think it is an injection pump timing issue since the 'S' pot adjustment effects the low-RPM injection advance.

Try changing back to the stock chips and see if the car drives the same.

Oh, drink plenty of orange juice and call us in the morning

Peter I was just going to say the same thing! Mickey, I would check what sensors affect timing---black smoke indicated it's off---good luck!

------------------

Yes, I agree that it could be a timing issue. It's almost as if the ECU is having a difficult time keeping the timing in adjustment at low rpms. It could be:

-Bad Wett chips (I'll swap my originals back in tonight)

-Bad ECU (Yikes! $$$)

-Timing belt skipped a tooth, or a sprocket is loose. (Double yikes!)

-Bad injector pump. (Help me, Jesus!)

-Bad timing sensor. (There are two of them. One is the needle lift sensor, and the other is the cam position sensor, wherever that is.)

Anybody know how to test the Needle Lift Sensor?

-mickey

Could just be a single clogged injector too. Sorry to hear the evil beetle has a temporary cold, I'm sure it will blow it out in the end!

Mickey
My sister lives in Stansbury and I stay there alot of the time. Or I stay at my in-laws house in Bountiful, but I call home Manti. I drive from Manti to Salt Lake just about every other day.
Anyway, thanks for all your input on Flying J. I will just fill up at stations that are off the freeway.

You don't drive that white Passat TDI, do you?

-mickey

OK. I got home this afternoon (left work early to mess with the Evil Beetle) and hooked up the scan tool. Apparently, EB saw me coming with the stethescope because he's right as rain once again. No codes of any kind, pending or saved. I didn't notice any strange behavior while driving home, but that didn't surprise me because it was working fine while cruising on the freeway. The problem only happened at rpms below 2000 and with very light throttle. (Or at idle early in the morning.) But when I got home and hooked up the scan tool, I could not get the engine to repeat the behavior!

Oh, well. I don't care how it gets fixed, as long as it's fixed. I'm sure the problem will reappear one of these days, and I'll eventually get the scanner on there in time and catch my gremlin in the act!

The rain is gone, so everything had a chance to dry out. If the wet weather had anything to do with it I'll have to wait for another rain storm to experiment further. Temperatures reached the mid 50s, too, so maybe the warmer weather helped. I also dosed the care with my usual winter brew of Arctic Express and Amsoil Cetane Boost, and added an ENTIRE BOTTLE of Chevron DieselMotive injector cleaner! (Enough to treat 100 gallons!) If the problem had anything to do with gummed up injectors or anything like that it's solved now!

While I was at it, though, I messed around a little bit and tried to measure my turbo boost. See the Power section for the next chapter, entitled "Check My Math."

-mickey

Mickey
No, but that to would be nice. I have a White 2000 Jetta GLS. If my E-mail was working I would send this that way. Sorry I have a bad ISP,"it sould be working by Friday". Well I hope the cold is gone. That would bug the @#$* out of me. It could have been a injector need a good cleaning. My Merkur will do something like that and I have the injectors cleaned and it will be run just great. But, would think gas and diesel injectors might not act the same way.

[This message has been edited by karmann ghia (edited February 22, 2000).]

Mickey,

Would air in the fuel line possibly cause your problem ?? (the old bubbles in the line) ???

Gary

Did you have the lower cover installed when you went through the rain?

Mickey, I've been living with this same, exact condition for over a year, and have given up on trying to fix it. As you reported, no error messages, and everything else checks out. It hasn't changed in 25000 miles, and I don't expect it to change. Temperature, fuel, moisture, etc. make no difference. Mine's a 98 Jetta TDI. I'll be watching to see if anyone else has found a real cure! This intermittent problem can be very annoying (as well as hard on the C/V joints!) I wish you luck.

No sooner did I send my laptop away with my wife this morning than the Evil Beetle's gremlins are back to work! The car had great difficulty maintaining idle until it got fully warmed up, and when I'd try to hold a single low-rpm engine speed with zero load (tranny in neutral) the rpms would see-saw up and down. Once the engine was fully warmed up it would idle just fine, but there would be a momentary hesitation when I'd apply throttle, followed by a sudden "rush" of power as the fuel injection kicks in. Imagine lifting your foot off the throttle and allowing the engine to coast down to about 1500 rpms with the injectors shut off, then stepping on the pedal again. Power should come on instantly. With my car it's almost as if there is a very brief hesitation before the injection recommences. (Like a carburetor with a bad accelerator pump.) That is accompanied by a BIG cloud of soot!

I doubt that air in the fuel lines would cause the problem. Any fuel supply problem, or even fuel contamination problem would tend to get WORSE with more throttle and higher loads, not better. I think the fuel is flowing from the tank to the injector pump just fine.

This has got to be an electronic problem of some sort. Some sensor signal is not getting through properly, or there is a problem in the ECU itself. It might be temperature related, since it was a lot cooler outside this morning than it was yesterday afternoon when the car was running fine.

-mickey

Karl: Lower cover was in place. The car has had plenty of time to dry out, so I doubt that the rain was the culprit. It had been acting up a little bit in the mornings for a couple of weeks, but the rough idle would resolve itself in a few seconds.

-mickey

Mickey:

The TDI's ECU calculates engine speed via a G28 Engine Speed Sensor. This sensor in turn supplies a TDC signal to the control unit that "calculates the actual point of commencement of fuel injection from the TIME DIFFERENCE between the needle lift [sensor's] pulse and the TDC signal supplied by the engine speed sensor."

http://www.vw-industrieverkauf.de/englisch/kommunikation/pdf/tdi-technik-eng.pdf
See pages 5 and 10.

Thanks, guys! That's exactly what I needed to know.

-mickey

Isn't is weird that the mil doesn't go on? It would seem to point to a non-sensor failure, or at least a non-total-sensor failure. So the conditions that the ecu sees are what it considers plausible.

EGR is a low load kind of thing isn't it? A

I must say I’m shocked at all of you, not one person has asked mickey how he or his family is yet.

It’s a sad, sad day when a car comes before your welfare.

How you all doing mickey?

Right that’s the PC bit out the way, have you tried the original chips back in yet?

We're fine. Sean has a really scary, croupy cough but it sounds a lot worse than it is. In fact, he seems to think it's funny for some reason. (3 year-olds are easily amused.)

I haven't had time to mess with the chips yet, but that's one possibility to explore. Actually I've got two sets of Wett chips: The original ones, and the "version 2" low-smoke chips. I'll put the original ones in and see if that helps. I'd do it tonight, but I've booked time at a computerized golf simulator that will allow me to play my choice of several world class courses while simultaneously providing precise feedback on my golf swing. (Club head speed, plane, open/closed, etc.) I need to figure out why my swing goes from outside in all the time, and the clubhead is too open. I think I need to open my stance a bit and concentrate on clearing my hips earlier. Or something. (I HATE golf! HATE! HATE! Sigh....)

-mickey

oops, accidentally hit enter.

Anyway, what would a stuck egr valve do?

Things could point to mechanical malfunction, since there is no mil indication.

I always thought that a “computerised Golf simulator” was what a VW dealer used to sell a certain model of car when they ran out of demo cars

I need to think very carefully about what each sensor does and what its effect is. It's possible that a sensor could be malfunctioning and the ECU simply doesn't realize that it's not "normal." The computer might be thinking "why is this idiot turning the key on and off all the time like that?" Know what I mean? I think On-board diagnostics is overrated. The throttle position sensor, for example, could die totally and the ECU would have no idea. How does it know whether the sensor is broken or whether you just like to idle your way from New York to California as some kind of frat prank? And as SkyPup pointed out you can completely remove the IAT/MAP sensor and plug the hole, and the ECU is none the wiser for it. This will have to be a triumph of brains over silicon, I think.

-mickey

p.s. Anybody watch "Who wants to marry a millionaire"? That was NOT a triumph of brains over silicon!

I ran (mistakenly) 50 miles over the weekend with the duct from my MAF sensor disconnected. Low power on hills was tipoff. No MIL.
The thing is, it really wasn't an electrical failure, per se.

There's that whole brake/throttle lockout thing. I mean, one of the brake switches in the 2 in 1 combo switch could be sticking periodically and even though the switch for the brake lights work, the switch for the ecu could be sticking.

You could probably get that stuff that facilitates electrical connections, take off the leads of every sensor you find, dab some on, and put it back together.

Maybe that could be done with the ecu too. VW recommends using the goop mentioned above, (I forgot the name), every time a connection is opened. (I'm thinking ecu changeout here for new chip installation)

You've checked the vacuum and boost lines?