i re-did my valve adjustments recently coz my mechanic adjusted it with the engine hot and is a little bit tight but now the a/f gauge behaves differently.

before:
-when i'm accelerating slowly the a/f gauge will jump to rich side and when i let off it will jump to lean or sometimes over board then come back to rich side again which i believe is normal.
-also, when i'm at idle it stays on the rich side.
-if the engine is still cold, everytime i make a stop and press on the clutch the rpm drops to near stalling(mechanic says cause of rich mixture).

now, after valve adjustment:
-when i'm accelerating slowly, a/f stays on the lean side when i let off gas a bit a/f jumps to rich. wtf?! but when i really step on it, a/f jumps to rich side.
-when i'm at idle, a/f stays on the lean side most time then jumps to rich side on occasion.
-when the engine is cold, rpm doesn't drop as much as near stalling as before. (could it be cause of lean?)
-throttle response is better(this is the only positive result)

i followed helms manual in adjusting the valves and i used 0.007" intake and 0.008 exhaust. i made a mistake coz i intend to do 0.006" intake and 0.007" exhaust so i might do it again.

from the before and after comparison, is there any error in the valve adjustments? why is my a/f behaving strangely like opposite of what it was before? could it be that i'm really running lean? does valve adjustment alter a/f?

any help will be appreciated.

 

What O2 sensor are you using? wideband? What A/F gauge?

 

i'm only using a 4-wire ntk sensor and an autometer a/f gauge. i know autometer are not accurate but they can be use as reference and the way it behaves is different after i did the valve adjustment. it's not like this before only after the valve adjustment. so the inaccuracy of it does not really play a part here right?

 

I wonder if they were tight enough to not seal properly? Maybe the valves did not close tightly and let some gasses out all the time. Let off the gas at higher revs and no,or little, fuel is injected so the gas leaking out would be lean. Under normal running or acceleration, unburned gas leaks out before combustion which shows rich.

If this is what was happening, I hope you did not run it too long this way. The valves and seats can get burned easily that way. The valves get rid of some of their heat through the valve seats, if they do not seat properly, no heat sink, overheated valves.

 

if your valve are set to tight you will have your fuel mixture being burned in your header and not your combustion chamber.

check valve adjustments again and check tps. also look for any vaccum leaks.

 

which is more detrimental, tighter clearances or more loose?

 

too tight and your car will barely hold an idle it will be loping heavily.