Car problems... desperate

[maciej-xx]

OK, at this point I am really I am really desperate. My car is driving me (and mechanic) crazy...

It is 98 A4 2.8 MT with 156k miles

Couple weeks ago my car just would not start. It was cranking but not starting. Occasionally (first thing in the morning) it would start for 30 seconds or so and then die... and not start again. Spark plugs, wires and valve cover gaskets were replaced. Still nothing. MAF, crankshaft position sensor, camshaft position sensor and ECU were switched from another 98 A4 2.8 That did not help either. We have done what we could and finally tow truck takes my car to the shop.
Next morning, they go to the car and it STARTED. They could not tell what could be wrong with it. The car was starting with no problems for next 2 weeks.

After those 2 weeks same problem comes back... Luckily I was able to drive the car to the shop (different this time). Mechanic replaced Ignition module but that did not help either. Tomorrow, I am supposed to take the car from them because they have no idea how to fix it...


I just remembered that, in the place where the battery is, there was a lot of water prior to that. Could be ECU affected?

area where the water was

[Affinitive]

You need a different "Mechanic". We tend to go by the term "Technician" now a days. Sorry couldn't help it. But you're obviously taking your car to a general mechanico (also known to some as "Grease Monkey"). What do you expect. I'd also like to point out that this car doesn't have an ignition module, so to say. I guess you mean the mechanico started throwing parts at the car, one being the coil pack. Did he even bother to check TSB's. Not likely, cause he would have been on to something finding a TSB about the coolant temp sensor, updated injectors and hotter thermostat (92 instead of 87 degree).
The coolant temp sensor is most likely the main contributing culprit.

Don't mean to be a prick, but it really irritates the sh!t out of me when I hear and see the general mechanicos throwing random parts into cars they have no clue of. How much did he charge to replace the coil pack??? A good tech will refer you to someone capable of dealing with this kind of a car. Let me guess, he didn't even mention anything about the cracking/leaking expansion tank you got there, eh. I'm talking abou the coolant resevoir with all that yuky looking pink residue all over. get a new cap too and both parts from the dealer only. The only aftermarket stuff I know of is junk when it comes to resevoir and caps.

As for the water you mentioned, the plenum/ecm boxes seal very well. Seen a fair share of B5 chassis cars with battery compartment/cowls filled with water and not cause any damage to the ECM. Also the water will come inside the car far before turning the ECM into a submarine. Did he at least clean out the cowl drains???

C

[prodrive]

I would check all the cable connections through the ECU and the sensors probably you should have lose connection somewhere else,first check the MAF cable since you installed CAI ,Vag your car too.

[docurley]

I would also say swap out the coolent sensor it's quite cheap and you can do it your self.

The 2.8l V6 engine (both AHA and ATQ) have a temperature sensor attached to the hard coolant line that crosses from the passenger side head to the driver's side head below the throttle body. This sensor feeds information to the ECU, as well as the dash for the temperaure gauge.

The position of the sensor is closer to the passenger side head (it's almost below the cam chain tensioner harness).



Of course, it's not just as easy as opening the hood and changing this piece. Being that it's down low on the back of the engine, there are things that you'll need to remove first.

Start by removing the engine trim cover, and the trim for the airbox lid. Remove the intake hose from the airbox and the hard intake duct.

Next, remove the 10mm bolt from the top of the intake duct, and the harness for the intake temp sensor. There are 2 tricky steps on removing the intake duct from the throttle body. I'm sure replacing the coolant temperature sensor can be done with the intake duct in place, but removing it makes it easiser.



Tricky step one is removing the PCV hose from the driver's side of the intake duct. Squeeze the clips together and slide it off. This is easier said than done. I use long forceps, or a pair of screwdrivers in a chopstick arrangement to do this as my hands are too large to fit down in the area where this connection lives. Once you get the PCV hose removed, proceed to step 2.

Tricky step 2 is removing the bolt that holds the intake duct to the throttle body. There is only one, and it's on the driver's side top of the duct. it's an Allen, the I believe it's a 6mm. I use a 1/4 socket and very short extension or palm ratchet on these once broken free. Have your LONG magnetic probe handy for when you drop things. Not if, when. On the A4, the gap between the engine and firewall is about 2 inches. On an A6, there's a lot more room to work.

Once you have the bolt, the PCV hose, and the IAT sensor connector off of the intake duct, you can pull it off of the throttle body. Now is a GREAT time to clean the throttle body by the way.



As you can see, having that intake duct out of the way makes it a lot easier.

Now, using a screw driver, GENTLY pry the green clip off of the sensor, and pull the sensor and O-ring out of the hole. Clean any dirt out of the hole, insert the new O-ring and sensor, and start putting everythign back together. Make sure that the car is at cold temperature. Remove, and then re-attach the expansion tank cover. This will remove any pressure, and hopefully put the system under a bit of a vacuum, so that when you remove the sensor, the coolant doesn't gush out. When i did this on my car, I did not lose one drop of coolant from this hole, nor did this introduce any air into the system.