**** work in progress - I can't work out the way to get all the pictures in the posting but I'll keep at it so forgive the scrappy appearance in the meantime.
I've been getting P1172 & P1173 error codes recently (Fuel trim limits), and after eliminating other causes decided that at 92,000 miles maybe the injectors needed cleaning. I'd like to have sent them away for an ASNU clean but we need the car every day so I decided to tackle this myself.
It's not a difficult job but it's always good to know what to expect beforehand so I thought I'd put this procedure together for anyone else who wants to try this.
The cleaning worked, the error codes have now disappeared and there's a bit more zip to the engine now.
I can recommend the fuel injector seal/filter kit from Mr Injector, mine was Kit 18 for the Bosch 0280 155 769 injectors fitted to my AR32301 engine.
Do this with a cold engine as a small amount of petrol comes out during the process:
1. Remove the engine cover (remove oil filler cap, undo four ribe screws and lift off) replace oil filler cap.
2. Unclip the four injector electrical connectors by squeezing the metal springs and pulling them off. Also remove the variator solenoid connector in a similar way. Lay all cables rearwards out of the way
3. Undo and remove the two T30 torx screws that hold the injector fuel feed bar to the cylinder head. These may be stiff as it looks like Alfa used thread sealant on them.
4. Pull carefully on the bar and it should come upwards with the four injectors attached. Pulling up gently from one end helped as it meant the injectors came out one at time, but remember the bar is plastic so don't lever it too much!
Place the fuel bar and injector assembly on a towel on top of the engine.
5. Look at the ends of the injectors and see if there's anything leaking or any damage can be seen. Each nozzle has four tiny holes that the fuel sprays through.
6. Loosen petrol cap to depressurise the system (important)
7. Unscrew the plastic cap on the left hand (passenger) end of the fuel bar and press the inner valve cap with a blunt instrument whilst holding it over a plastic container. This allows a small amount of residual petrol to come out of the fuel bar.
8. Using a flat bladed screwdriver, remove the U-shaped clip holding each injector to the fuel bar. If you open the ends of each one a little it will unclip then slide backwards. Pull each injector out of the fuel bar, and watch for dribbles of petrol from the fuel bar (hence the towel). This one has left its o-ring in the bar:
9. Clean the injectors in paraffin and rinse with carb cleaner. Remove old O-rings and discard. Clip off plastic washers with wire cutters and discard. To remove the filters, insert a self tap screw enough to bite, clamp the screw in a vice with a washer to protect the injector and a spanner inbetween the washer and the vice then you can pull and lever them out as shown:
10. Make up an injector actuation cable (a 6v lantern battery, one push switch and two small insulated crocodile clips) and a feed pipe (plastic petrol pipe heated and streched to fit over the injector body, and an inkjet filling syringe). Spray some carb cleaner into the open syringe, replace the plunger and press whilst activating the injector. You should hear it click and see a spray pattern from the nozzle. Look at it and see if it looks symmetrical (there are four tiny holes so there should be four tiny jets). Repeat whilst you're still having fun with this for the other three injectors. Then connect the syringe pipe to the nozzle end and repeat the process. You won't see any spray but it will back rinse the injectors.
11. I was planning to use an ultrasonic bath to finish the cleaning of the injectors but it didn't arrive in time and we needed the car, but if you have one they are good to use, and remember to actuate the injector whilst it's being cleaned.
I repeated the cleaning process in both directions with water and detergent and after a bit could see that the spray pattern seemed good on all four injectors so I re-fitted them without any more cleaning.
12 Fit the eight new O-rings and press on the four plastic washers, and press the four filters in (this can be done by hand with the injector upside down pressing it onto a piece of wood). Spray the O-rings with carb cleaner (Toolstation £2.68 for 400ml) as this leaves a small residual film of oil which greatly assists fitting the injectors into the fuel bar and the inlet manifold.
13. Press each injector into the fuel bar, re-attach the U-shaped clips (check they really do clip in place, look at the sides and make sure they are parallel) and make sure the holes in the cylinder head are clean, then carefully align each injector with each hole and press, they should go in easily. Fit the two torx screws (clean the threads of old sealant), re-attach the connectors to the injectors and variator solenoid, then tighten the petrol filler cap and switch the ignition on, and check for any leaks. If everything looks ok, start engine.
14. Now you need to reset the self learning parameters using the OBD connection and a laptop with AlfaDiag or similar. This was important for me as the stored values of fuel trim offsets were near the limits and needed to be returned to default values.