My 93 nissan D21 truck with 4 cylinder 2.4L. Started idling high, besides that it won't pass emissions the hc is extremely high and I've done ngk plugs wires and cap and rotor the hc was around 2200. And Co same area

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All the parts are shown here and there are thumbnail diagrams you can expand.

https://www.nissanpartsdeal.com/oem-nissan-hardbody_pickup_d21-vapor_canister.html

More here and on the images tab.

https://www.google.com/search?q=1994+D21+4+cylinder+EVAP+parts+diagram

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as long as you have no check engine light on change oil, air filter. pep boys sells a product called guaranteed to pass add to fuel make sure car is hot when you go back for emission test cold car has high hc levels it also helps to post the hc level you tested at and the limit on your receipt hope this helps

you should not have to worry about it with the age of your car. nothing is wrong take it somewhere else to be tested

If egr valve is stuck open can cause raunchy smell from exhaust, hense high readings. usually this causes rough idle though.

Replace your oxygen sensors.
murf427

mccartlidge. are you serious?? high HC is the result of a headgasket problem??? do everyone a favor and dont give advice when you clearly dont know a damned thing about emissions. as far as solutions to your high HC output, someone else mentioned the possibility of a worn out cat along with carb problems and or a simple air fuel adjustment. this car if i remember correctly has a feedback carb which means it has an oxygen sensor and a mixture control solenoid on the car to fine tune the air fuel mixture. it is not uncommon to have a oxygen sensor not functioning at all or out of normal calibrated range. easy test for oxygen sensor(single wire oxygen sensor ) is to hook up a voltmeter at 0 to 1 volt range(positive lead to oxygen sensor wire, negative lead to any good ground source) and watch the voltage. a perfectly working system the signal should look like a wave constantly rising and falling from .9v-.1v. test at 2500 rpm as well as at idle on a hot engine.if the oxygen sensor doesnt rise and fall, add fuel(spray small amount of carb spray) into carb while at idle or high rpm and the oxyen sensor should go full rich(approx .8-1v) that is point 8(.8v) not eight volts. you will usually see a reading of .9v . if the oxygen sensor doesnt put out a rich reading than its no good. on the other end you can remove a vacuum line(brake booster hose, half way removed as to not stall the engine) the oxygen sensor should go lean which means around .1 volts. if the oxygen sensor does not respond correctly replace it. beyond that, the engine first and foremost has to run on all cylinders to run clean and efficient. if it has a missfire or dead hole that will cause high HC along with high CO as unburnt fuel is going out the tail pipe. i could go on and on about possibilities but figured i would give you a couple basics to go on. Good luck.

The master is beside the brake master cylinder, between the brake cylinder and the fender. Follow the line down to the trans, it ends at the slave. Now that you know where they are... why do you want to know??

sounds like you have a very dirty mass air flow meter. invest in a new one and be sure to clean the throttle body with an appropriate cleaner and tooth brush.

Hydro Carbons are usally from an engine missfire. It may be that it is such a sligh miss that you cannot feel it. What is your timing set at? I would try setting it at 2* advanced and see what that does for you.

possible but could be head gasket or valves , or worn rings and is by passing the pistons going straight out the end ...or maby settings are wrong ? try carb cleaner and inspect visually air-filter etc.