green coolant temp sensor faulty? poor mpg

[jedge1.8t]

my car was running one notch over on the hot side, and fluctuating back and forth, fans would turn on and car would go right back to half.

I already had the green coolant temperature sensor, did the air bleed from the coolant systems and did tons of tests.

vacuum test was solid, compression test was solid, the only bad test was my leak test - 30% leak on cyl. 3, no hydrocarbons in the coolant, none leaking.

after doing this I just ended up replacing the green coolant temp sensor with another spare I had.

Now I dont seem to be running hot anymore, it stays at the middle notch.

however my MPG has been a steady 19.5. I feel that is terrible and should be relooked, any other sensors that may contribute to poor mpg? i wanna go back to 24

[TheMel]

I would think that your MPG could be attributed to the compression loss, but I'm not going to swear to it.

[jedge1.8t]

my compression is good but the leak in #3 is excessive

[TheMel]

I misread haha

[jedge1.8t]

I have 01 225TT quattro. i swapped the head, all gaskets replaced, new coolant/oil, I got a APR stage 1 tune, TSFI coils and .40 gapped plugs.

Today i was sitting at a light and once again the temp moved to the next notch over, but once i picked up speed it moved back to the middle. My MPG avg. still reads 19.5

The cold starts take a awhile for the engine to crank, and then there was a SERVICE! on my start up which i never recalled, i will try and vag-com again to find the culprit.

idk whats going on but its killing me, maybe a maf sensor, other faulty sensors? Im first going to start with the fuel filter which probably never has been replaced.

[groggory]

With car hot, turn a/c on

Both fans should be on hi

Turn a/c off. What do both fans do? What temp does vag com read?

Go for a drive. What temp does vag com read while you're driving?

Go for a drive in the city and highway. Log block 001 the whole time. Post it up

[jedge1.8t]

thanks grog, problem is I let out all the freon on my high pressure A/C when i was replacing the head, but I will be evacuating and recharging on tuesday. right now the A/C wont turn the fans on because of the pressure switch isnt at threshold cause of low pressure outside of threshold.

whenever the car does go to the next notch on the temp the fans do activate and the temp goes down.

my coolant temp reads between 94c - 98c.

I will definitly do the vag log though, trying to get familar with this ross tech stuff

[groggory]

thanks grog, problem is I let out all the freon on my high pressure A/C when i was replacing the head, but I will be evacuating and recharging on tuesday. right now the A/C wont turn the fans on because of the pressure switch isnt at threshold cause of low pressure outside of threshold.

whenever the car does go to the next notch on the temp the fans do activate and the temp goes down.

my coolant temp reads between 94c - 98c.

I will definitly do the vag log though, trying to get familar with this ross tech stuff

Go read my vag com FAQ. I have lots of good stuff in there

[jedge1.8t]

Grog can you link me to your vag faq.

I ran some tests to.
Idle rpm 720 - 760 but occasionaly sags to 680
Coolant temp 95c - 99c then fans turn on repeated process
Occasional misfire but misfire sum goes back to zero.
Idle value -.2% and part throttle 7%

Im starting to believe its my thermostat. I probably got a cheap one out of spec. It was a 88c one if i remember correctly