Old Mk1 Avensis 1.6 Lean Burn Engine

[bri5055]

Got a old mk1 avensis 1.6 with lean burn engine 4a-fe. Looking for info on how the engine operates with regards to the butterfly valves on the air intake from a swirl control valve and vacuum switching valve. Have a haynes manual and no info on this is to be found.

The problem i have is the swirl control valve linkage broke a few years ago which i managed to repair. And on its next MOT engine emission jumped up (to much fuel hc?). Have now noticed there is any adjustment screw on the swirl control valve. Think this maybe the problem and adjustment required on the swirl control valve? need more info to understand how this works as the adjustment screw would seem to open the butterfly valves.

Have googled for info any help would appreciated

[Konrad C]

If you are talking about the vacuum switch which operates the on the inlet manifold, blocking 4 of the inlet valves, then there has never been any mention of adjustment or settings. If there is a set up procedure, it would be in a workshop manual. I may involve removing the inlet manifold.

With the engine on, the switch moves the butterfly valves to set position depending on throttle load and engine speed. Switch off the engine and the switch goes into a 'park' position. You need to observe how the lever moves when using the throttle.

When I reconnected my switch back to the lever, I never touched any adjustment. I enquired about the switch and was told it only sold as a complete unit - inlet manifold!

This is not an easy subject.

[bri5055]

First of all thanks Konrad C

Have now upload a picture of the component and the adjusting screw. Taking a closer look at it i think the screw used to be wound fully back have now screwed it in to what looks like old lock tight marks on the screw. Car is now going for a MOT retest on Saturday after only failing on emissions(hc).

[bri5055]

Update car passed MOT on Saturday struggled on emissions W reg 131k on clock screw in on the adjustment screw and it just passed. Hope to remove the inlet manifold for inspection in the future and maybe change the lambda sensor

[Konrad C]

Can you give the details of the emission test. The MOT tester usually supplies a printout of the emissions.

My last test in August 2012 gave the following: Fast idle (0.2) - 0.01, HC (200) - 11, Lambda (0.97-1.03) - 1.021, CO (0.3) - 0.008.

My car is 1998 1.8 with 125k miles, and as you can see, the car has kept with the very tight limits.

When you adjusted the screw, was it done whilst on the emission machine? Did you make a note how much adjustment was needed and which direction to turn the screw?

Hope hopefully it should be fine.

[bri5055]

MOT results 22/06/13

CO <=0.300% 0.175% PASS

HC <=200ppm 381ppm FAIL

Lambda 0.970-1.030 1.007 PASS

natural idle <=0.500% 0.025% PASS

MOT results 30/06/13 after adjustment of screw turned about 1 turn clockwise on the screw head(this should just crack the closed air inlet ports open i think)

CO <=0.300% 0.243% PASS

HC <=200ppm 124ppm PASS

Lambda 0.970-1.030 1.012 PASS

natural idle <=0.500% 0.228% PASS

*NOTE DO NOT ADJUST THIS SCREW TO PASS MOT I HAVE ADJUSTED MY SETTINGS BECAUSE THE SWIRL CONTROL VALVE BROKE AWAY FROM ENGINE AND HAD TO PATCHED BACK TOGETHER.