Cleaning the CIS Airflow Sensor

CISMAFiconThis tech procedure is about cleaning the CIS airflow sensor for better running, and fewer starting and idle gremlins…

The following article is an ATS Technote

ATS logoAfter a few days of doing the timing belt and numerous adjustments to the car, it still had a cold start problem, no longer as pronounced, but still remained.

My Brother listened under the open hood as I turned over the ignition to get a clue on what could be the problem, he noticed a BUZZ noise that was much louder than usual (once the car actually stayed on idle by itself) coming from the fuel injection system on the top of the air box. [this buzz is actually the frequency valve, controlled by the oxygen sensor. I suggest oxygen sensor replacement before you attempt this procedure]

After verification with the Bentley, we discovered there was a piece that should be cleaned from time to time to ensure proper flow of fuel to the injectors. “The Plunger” is the part that connects the airflow sensor to the injection system, it is a valve, augmenting and lowering gas flow to the injector system. After cleaning it out, the car starts every time, cold or wet, at first turn of key.

[Proceed with caution – these are delicate parts and are very expensive to replace, do this procedure at your own risk.]

This tech-note has 17 thumb-nailed pictures… 

CISMAF1 This is the fuel distributor. The valve is in the part with the fuel lines connected to it.
CISMAF2 Using a pair of vise grips “long nose” style, gently squeeze the tubing coming from the fuel filter to the injection system, DO NOT pinch the line, you only need as much pressure as to prevent gas from pouring out. below it is a bolt, crack it open, remove bolt and copper washer.
CISMAF3 Next to the line you just closed, a line leads to the firewall side of the injection system, gently crack the line open, and save the bolt and washer.
CISMAF4 Lastly, on the battery side of the injection system, one last line you need to crack open , and remove the bolt and washer.
CISMAF5 There isn’t much of gas pressure in the area, though I used some absorbent shop cloths, they are really to prevent from fuel being dropped on asphalt (eats through it)
CISMAF6 There are three flat head screws (the engine side one might require to loosen an injector line and move it temporarily) remove the screws.
CISMAF7 Gently lift the injection assembly from the air flow box, the plunger should be partially visible as it sits resting on the edge of the travel
 limiter ring.
CISMAF8 gently pushing on the plunger, you will feel (and see) if there are debris inside the shaft ( it should move up and back smoothly, without having to pull on the tip to make it come back in place.
CISMAF9 Right below the tip of the screwdriver is a lip, preventing the bottom from coming loose, you will need to flatten this upwards to remove the nut
 of this assembly.At this point before going to the next step you should mark on the body where the travel limiter ring position, as you will need to return it into the same position when reassembling.
CISMAF10 Loosen and remove the bolt, and travel limiter ring, holding the tip of the plunger gently in place (do no use excessive force to hold it in position (IMPORTANT! see why below!)
CISMAF11 slide the plunger out gently, until the soft return spring comes out with it. remove both from the unit. Using a soft cotton ear-swab dipped in gasoline, clean out the residues inside the injector body shaft.
CISMAF12 I noted a few scratches that were probably my cause for hesitation on idle on the plunger, using 600 grit sand paper, and using wetting agent (in this case power steering oil) I gently sanded the scratches from the shaft of the plunger until it returned to the original shining metal it was supposed to be, patience and gentelness is important as this part cannot be
 purchased separately of the injection unit from a dealership (which is a mere 850$ in itself)
CISMAF13 once the plunger was done, I turned my attention to the air flow box. It wasn’t too clean…yes this is the cleaning tip!
CISMAF14 here is a reason why you should NOT use carburetor cleaner to spray under the air box to clean it out – it collects stuff if improperly rinsed out afterwards. Clean it by hand with a cloth dampened with fuel.
CISMAF15 All Done. I finished by sanding evenly the 3 rest points of the injection assembly so that the plunger would be at the optimal angle of action once re-assembled.
CISMAF16 slide the spring back into the injection assembly followed with the plunger making sure you have wiped the plunger with fuel first. Set the limiter ring in its original place and hand screw the nut back in place, tighten it down.
CISMAF17 don’t forget to push the locking flap back in place, to gently put the injection system back on the air flow box, screwing evenly the flat head screws back in, then reconnect the 3 gas lines to the unit, check for leaks,
 release the fuel line. Try to start the car, it WILL take a few turn of engine to start – until the air has escaped the system, it will be a rough idle, but it should settle down inside of 3 to 5 minutes..

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