Loud ticking on passenger side underneath aftermarkert air cleane

Did you adjust the idle mixture screws ? Is this a two or four barrel carburetor and what make carb. Carter , Holley, Quadrajet etc.. What make vehicle is it ? Normally the idle mixture screws should be opened 1 and a half turns to two turns . counterclockwise from fully seated . Then you can set the idle screw to what the idle should be 600 rpm to 750 in drive . Most cars have a decal somewhere under the hood telling all these things !

Not sure if there is a question here or not. If the pressure is always below 40 and you are hearing engine noise, chances are the oil pressure really is low. You could replace the sending unit or use a mechanical gauge to verify.

double posted
post RPM in both modes,
it must be the same
the ISC idle controls system controls idle at all times.
post RPM. 800 is normal. the exact valve is in the FSM
and posted under the hood in USA.
no country stated in 4000s posts so.... well, gee....
here, open the hood, look up, see EPA vacuum map
that is also the the engine size and type , and most state the normal
hot RPM clearly there, and is in the FSM.

here is the acid test. hot.
in park hot, rpm 800 if not the ISC fuction is dead
"idle speed controls"
good? yes.
then select drive. if RPM drops ISC is malfing.
now back to park. (all this is in the FSM to read)
now 800 hot. you turn on all heavy electrical loads
the rpm does not drop. Head lights + heater fan, and defrost.
all these test he ISC, if it fails its bad.
what does bad mean, that means its out of control
and you do further testing to find the reasons.

vast reasons.
Ill name 3:
intake air leaks. aka vacuum leaks.
ISC valve dirty , clean it.
throttle cables , misadjusted.
cold start air valve stuck open hot.

May be under the valve cover. Lifter may be going flat or tappets loose or bad pushrod. don-ohio (:^)

Sounds like an Exhaust Manifold leak on only one cylinder. The Gasket is probably blown out. Check around where manifold is bolted to the engine. Any leaks are usually evident by a black sooty deposit.

check for vac.leaks these will cause very poor idle.

Sounds like a vacuumn leak.

You could have a simple vacuum leak or a faulty computer.Listen to the engine with the hood up to see if you can hear a loud hissing sound that indicate a vac leak

May be mice, but I had a truck that did that from a worn speedo cable.
Regards
Apeal

how old is the fuel filter? and have you checked fuel press at idle and while driving ? and does the car have a cat on it ? you can get car at operating temp and check the temp of inlet and the out let is it over 100 degrees difference? and the mass air you put on is a new oem ?