Greetings!

I have an 1999 Mk1 Combi Octavia with 1.8l NA engine.
I have had an good run with the car so far, but have stumbled to an problem now where I need assistance from more experienced ocu owners and car enthusiasts.

Normally it took ~2 cycles to start the car, aka it started instantly.  Few weeks ago I started having "problems" with starting as it took 4 cycles to start. The car ran otherwise perfectly fine.
Last week one morning the car wouldnt start at all. Start cranked normally, but no life. I hooked vcds up and had code of Engine speed sensor: No signal.
I was told that it can also show up if the engine wont get fuel when cranking. I solved that puzzle by spraying flammamble spray to intake and cranking with no go. Decided to change the sensor and got the car back alive again.

The first start after changing the sensor, I had to boost the engine back alive with spray. It took off really bad with only one cylinder firing, but after it started up it ran like new.

BUT. New problems emerged. The car needs up to8 revolutions to fire up now.

The engine reves perfectly in neutral, but when accelerating, it numbs down right after 4500rpm. Also if I drive with 1st gear and go up to 4500rpm and slam the gas pedal, it does absolutely nothing... Also, if I floor it on lower rpm:s it has an lag until it starts accelerating.
And for newest oddity since today, when starting. It may kill the start suddenly. It feels like it fires back against the engine rotation, but I dont hear any backfiring sounds. The cranking just stalls like its forced to stop. After I release the key and crank again, it fires up perfectly fine.

With my googling searchwords, I only get TDI and 1.8T turbo related problems. It feels like it could be fuel related problem, but there is some oddities on the behaviour so Im really not sure what is happening.

Has anyone experienced anything similar? Any suggestions where to start digging? Im reluctant of changing part after part until it revives, rather than getting to bottom of this and repairing things that are actually broken.

I will greatly appreciate any and all help.

Sincirely, Teemu.

 

 

Forgot to mention, that no new faultcodes have been showing up...

-Teemu-

Is the battery at correct charge and alternator all working properly? 

 

Check the simple things first...

Do you hear the fuel pump prime itself when you open the door?, also, when was the fuel filter last changed?.

 

I would check the state of the wiring to the crank sensor rather than the sensor itself.

 

Have you put a meter across the sensor terminals to confirm you have not got a defective new unit?

 

Was the sensor a genuine or patern part?

Thankyou for your answers.
Battery is perfect and also the charge voltages.
Fuel problems was the first ones I thought, but the problem was so consistently @ 4500rpm regardless of engine load, that it was not feasible.
After changing yet another crank sensor the car woke up like new.
The part was an widely used brand on vag's, but mysterious are the ways of cars!

Thanks for good pointers and good that the problem got solved!

Edited 10 April, 20197 yr by Palsteri