I know you guys hate when things get reposted without searching the forum, so ill let you know that i did search as best i could for answers and im lost..


here are my issues.

while driving,my temp needle goes down to nearly the C. when the car just idles in the drive way the needle is in the middle where its supposed to be.
but as soon as i start driving it starts to go down

the led ambient temp gauge in the middle of the dash, sporadically reads crazy numbers like -44 when its 70 degrees out. but sometimes it reads the correct temp.

i replaced the coolant temp sensor a week ago after experiencing some other problems and it fixed those issues so i know the sensor is good

i have reallllllly excessive and fast inside tire tread wear on both back tires. the car isnt lowered i have the stock wheels on for the winter. what could this mean, the fronts are good


finally...the cars idle dips down below 500 if i put in the clutch to start slowing down. but then the needle bounces back up and idles normally. it has never stalled i just dont know if this is something to worry about.



any info on any of this stuff is appreciated. i said a lot but im sure i left some things out ...just ask if i didnt give enough info

 

My needle bounces like that too occasionally. +1 for that! It freaks me out because I put in the clutch before a stop sign and it sputters then kicks up above 1 grand before lowering to the normal idle of 750-840.

 

Well for the temp gauge it's probably a bad thermostat. I don't really know about the sporadic idle. Do Audi's have idle springs?

 

my heat doesnt really blow hot either, unless the gauge is saying the temp is what its supposed to be. even after 45min of driving, kinda just barely warm air

so if it is the thermostat is it an easy thing to get to? 99 a4 1.8t

 

Your thermostat is shot or at least partially stuck open. Take that to the bank. Once you start driving the coolant flies right through the block without ever getting hot and then cools further in the radiator. Sitting still, there's no slipstream air to cool the radiator so it eventually warms up. Get moving and it cools right back down.

Get the car aligned - it sounds like an alignment issue of some sorts unless you have bent control arms on both sides. Have them give you alignment specs before and after they do it so you'll know what they changed to fix it.

For the idle issue, I'd suspect a small vacuum leak or a clogged vacuum line. Diva seafoam treatment on the vacuum system. If you have a clog it should free it and if it's a leak you should see smoke coming out of the leak. Either way it can help you find it. Tons of info through Search on seafoam.

For the screwy display, your ambient temp sensor is probably freaking out. It's on the front of the lower crossmember in fron of the radiator. Unplug it and clean the connectors with electrical contact cleaner to see if that helps.

BTW, you should create a signature on your User CP listing year, model, drivetrain, etc for your car - it'll help a lot and save repetitive asking later on with future questions about repairs or modifications.

 

how difficult is it to replace the thermostat? where is it located?

just went out and cleaned the temp sensor haha

thanks a lot for your help!!

 

There's a DIY here somewhere on changing the thermostat - check the DIY section here on AF, or look at www.audidiy.com or www.audiworld.com in the Tech section. One of them has a step by step procedure for swapping it out.