CRAZY_RUSSIAN

if you mean by low while driving, then its normal. also how do you know its reading low?

Loudgoldwing

I'll pull a picture of the locations of each the ECM-communicating sensor and the temp gauge-communicating sensor when I get home from the office today.

HOWEVER: CrazyRussian (and, anybody else for that matter) I have a question. Before I did this work on the vehicle, I would turn the key to start, and within 3 revolutions of the engine, ignition would catch and the engine would fire. It would idle really "thick and chunky," if you know what I mean, until the circuit would close, and then all would be well.

Now, after all of this work, the engine has to turn about 7 times when I turn the key. When it does fire, it only seems to hit on maybe 2 cylinders for the first 2 revolutions thereafter. After those first 2 "lubba-dubba" sounding revolutions, the engine races to life and then idles fine.

Is is possible that, after running wierdly for so many miles, due to a bad ECT sensor, dirty MAF, old spark plugs etc, the ECM profile needs to re-write itself after numerous "lubba-dubba" start-ups in order to compensate for what it perceives to be a different configuration?

Or, do I need to go through and re-torque my plugs or something? Once the engine is fully alive (and I really mean it when I say that it only takes 2 revolutions "dirty" before it cleans out and fires on all 6), open circuit or closed, she runs smoothly. That's what has me confused... But again, I admit that I'm a perfectionist when it comes to this kind of stuff.

CRAZY_RUSSIAN

7 times is way too many... try unplugging your battery and letting it sit for about 15 min, then replace the sensors, do the same thing if it dosnt help. and if all fails, you may have to decarbon your intake/engine. allot of ppl use seefoam and i have no experience with that stuff. i would recommend using BG products. i use it at least once a year, and usually ill get a crap load of smoke coming out in the process :-D

3L33ter

I suppose I don't know for certain if it's reading low, since I have no baseline to compare. But since the gauge has so many graduations and the needle hardly ever passes the second one, I figured it was low.

I was also wondering about the 4th line on the gauge, it has two dots surrounding it. Is this supposed to indicate where "normal" temp is?

Another reason for thinking it's running cold is that the engine is running rich and producing too many HC on the smog check.

Loudgoldwing

@3L33ter

The gauge reading you're seeing there is just about perfect. When we say our temp gauge is reading low, we mean that it will be right where yours is (normal), then for no apparent reason, the needle will drop to just above the "warm-up" area signified by the three lines in rapid succession at the far left of the gauge. Or, sometimes it won't even get up above that warm-up mark at all, regardless of the distance travelled.

The line with the little two dots is the boiling point of water. It is also the maximum adviseable temperature at which the engine is to operate for an extended period, and even then for less than 100 miles, if you would like to have your engine survive the experience unscathed.

Now, as for your "running rich" situation... this is likely caused by 1 of 2 things:

1) Thermostat. If your thermostat has ANYWHERE near 60,000 miles on it, get it, your water pump, and your timing belt replaced all at the same time. Replacement of the thermostat typically requires maneuvering it in and out around a loosened timing belt anyways. Since loosening the timing belt is the most time-consuming part of the job, and Audi recommends a 60,000 mile service interval, just replace it all. Do it yourself and you're looking at about $300. Maybe $50 more if you get the upgraded water pump with the metal impeller (a definite plus), instead of plastic. Pay somebody to do it, and you're looking at $500-$700.

Even if you owned a Kia Rio, that's only 2 months' worth of car payment and insurance for 60,000 miles' worth of peace of mind. Besides which, run rich long enough, and your O2 sensors and catalytic converters are going to start bitching and moaning. They are NOT a cheap date, either.

2) ECT sensor. (Dammit, I forgot to upload that location diagram again. Sorry) This is the easier (and logically speaking, the more symptom-plausible) culprit to deal with. Scroll down through this thread for the location, but mine ended up costing me $30 for the part, and $50 for the labor. Simply put, if this sensor isn't able to "travel" all the way up in its range as your coolant warms, your ECM never receives a signal telling it to lean out the fuel/air mixture because your engine has reached its proper operating temperature.

Basically, this means that you're riding around with your "choke" on all the time because your computer thinks the engine is cold all the time...


Now, we as 12V owners are in a really difficult situation, here. Basically, we have been given a vehicle whose system of factory-installed checks and balances is rarely able to maintain a "failsafe" status. How the HELL are we supposed to know if the thermostat is sticking open if our ground on the back of the gauge cluster is POSSIBLY loose, causing the temp gauge to read low? Or, maybe it's the four-prong multi-function sensor going bad all the way over on the other side of the engine bay?

It's like trying to make a peanut butter and jelly sandwich with a rubber knife. Sure, you can stick the knife in the freezer to make it stiff enough to spread the peanut butter, just like you can use the heater in our vehicles to see if the thermostat is really working properly. But, it this destined to be our fate? Coming up with "Jerry-Rigs" and "Dummy-Checks"?

As soon as I get everything on mine the way I think it needs to be, I'll probably publish a manual for the "real-life" maintenance of a 12V. This German-Engineering idealism I've been cursed with is really starting to chap my ***.

I don't know... and my pills are starting to wear off... I can hear the fu@king bunny-rabbits starting to sing again.

3L33ter

Hey Loudgoldwing,

Thanks for the reply. I'm a mechanic so the repairs/labor are no big deal. The timing belt, water pump, and thermostat were replaced right before I bought this car. The PO also replaced one temp sensor, but I don't know if it was the MFTS or the ECTS. I'll ask him if I remember.

The car currently gets about 21-22 mpg on long road trips. I've heard v6 audis don't get good economy but is 21 mpg good or bad? I thought the HCs might also be coming from an oil leak but I leaned towards rich mixture because I had thought my engine was running cold.



But a little more on topic- the gauge markings are dumb IMO. Either put numbers on the lines and let the intelligent driver interpret the reading, or make it really simple for an idiot by putting a white block for cold, red block for oh-isht, an one line in the middle for normal... just IMO. Thanks for the info on the gauge though.

CRAZY_RUSSIAN

that would make seance, there is no way they would allow that

coriard

I need to jump in on this. My 12v has been running rich with off and on white smoke (after the engine warms up) since I bought it 8 months ago. I've replaced the ECTS, the MFTS, and the Thermostat. Still runs rich. Any last ideas?

Loudgoldwing

@Coriard

I KNOW this isn't what you want to hear, but it sounds like your issue might be related more to oil than fuel/air mixture.

Please post reply with the work that YOU PERSONALLY have performed on this vehicle, so I can better understand your skill level, and offer you a few ideas commensurate with your abilities.

Please don't misunderstand me, here... I am NOT trying to blow you off... I'm just at the office right now, and some of the stuff I might get into is a little long-winded. If you're just looking for advice so you know how much your mechanic might charge you, let me know now, before I dedicate an hour of my day.

Thanks!
LG

coriard

Well while I have learned a lot about my car in owning it and trying to fix problems, from your perspective I'm sure my mechanical abilities are next to none. Plus, I don't really even have the tools here (college student) to give anything a try myself anyhow.

Thanks for helping! So yes, what might that mean, and how much labor from a mechanic are we talking?