2.0 FI, in a late bay I have had very little experience with FI models, so any help much appreciated. The van starts fine, and initially revs and idles as it should. However, as soon as you pull away and accelerate, it bucks \ kangaroos, to the point of being undriveable. This quickly gets worse as the engine warms up. I have checked for air leaks, and replaced any suspect hoses that I can get replacements for. No amount of carb cleaner sprayed anywhere now makes a difference to rpm, so I am fairly sure its not an air leak. I have replaced points, condensor, leads, rotor arm, dissy cap, to no avail Fuel pressure checked, sits at 30-35 psi, and is steady Timing correct Does anyone have any pointers? I have read temp sensors are often suspects, any tips on testing them, or is it just a case of fitting a new one and trying it? TIA
Download the AFM fuel injection troubleshooting manual, it tells how to test each component. Have you looked at the wiper and tracks in the air flow meter? Sent from my Pixel 6 Pro using Tapatalk
Have you a link to that manual Matt? I will check the track tomorrow, but hoping it’s not that, as that’s not fixable is it?
here ya go: https://www.thesamba.com/vw/archive...al/AFC_FI_Training_Troubleshooting_Manual.pdf might be worth checking the TS2 aswell What year is it?
If you follow the procedures and it's the AFM track you can move the track sideways a bit as a stop gap. It's all a bit of a pity as the technologies involved in making AFM tracks are fairly basic until you get to the laser trimming required because it's so basic. A combination of screen printing and pottery glazes.. Following some research I did on AFMs I was lent, it's a potential divider that measures the opening of the air flap and does most of the computation of how much fuel to inject in the way the resistance track is designed to output different voltages as the flap opens. There was an initial idea I had to buffer the output of the AFM as it turned out that on some worn AFMs you could still get a "good" reading if you drew less current from the wiper. People commonly connect a capacitor to the wiper output to act as a short term memory of the voltage when the wiper loses contact as it sweeps over a gap. An American company has a $900 solution using a modern AFM but there are other reasons why a spring loaded flap is used rather than an open tube with a hot wire element in it, as the inlet manifold vacuum will be a bit less without having to suck against the spring loaded flap.
As Matt says AFM track is a fave for bucking and poor running. And yeah, the screws can be loosened and board moved. TS2 can cause odd issues as well as it sends a temperature signal to the AFM. Bentley process is straightforward
Temperature sensor on the cylinder head is bad , check it’s ohms , If you can borrow a computer from another fi bus , do it ,
Not yet. Having gone through the tests in the manual that Matt posted the link to, I have found the TS2 to be giving wildly inaccurate ohms readings at all temps. I have ordered a new one from French land, as I couldn’t find any in stock in the uk. I will update when it arrives Friday.
I have one , you can just disconnect it or stick it to earth, but before any of that double check it’s got someone conductive to earth it well as they can suffer with inaccurate readings due to poor connection
Yours will be worth a millionty pounds now then! Get it on eBay quick! I did try just disconnecting it, but it just stalled.
Sooooo. With the wire earthed, the engine runs fine, but sounded and smelt like it was rich. With the wire unconnected, it runs roughy, like it had an air leak, or was too weak. In my mind, this what it should be doing, and confirms the TS2 is duff? Incidentally, the wire had properly corroded were it joins the TS2, and just fell off with a couple of wiggles.
