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First check real good for an exhaust manifold gasket leak. A leaking manifold gasket will resemble a lifter/tappet tick. If you find no sign of leaks then your problem could be a lifter/tappet that has started to collapse or a lifter/tappet is sticking You can try an additive sold at many retail auto parts stores and see if it helps free it. There are many different brands at the different stores, pick one, all seem to be the same anyhow. They'll state that it helps free sticking lifters.
You could also have a valve spring weakening which should be checked by a mechanic.
This engine is equipped with hydralic lifters and adjustments are not needed. The rocker arm shaft bolts usually do not back off or loosen but if you would like to check them you can with a torque wrench. The rocker arm shaft bolts torque to 30 ft. lbs.
Chances are the affected lifters will need replaced to rid you of the tick if it is indeed a valvetrain tick.
Shawn
ASE Certified Technician
PA Certified Inspection emissions, ASE Brakes Suspension, Lead diagnostic Tech.20 years exp
you would not have any smoke from a manifold gasket leak unless the engine burns oil and smokes out the tailpipe. Between Chevy V8 trucks, Ford V8 Vans and trucks which both have problematic manifold leaks that I see and repair all the time, none of them had smoke in the engine compartment. Check your manifold under the heat shield for cracks. Remove the heat shiel covering the manifold and look at the underside of it for black soot.
A good engine treatment for sticking lifters is Seafoam Engine Treatment.
You could change the springs youself and would need compressed air and a fitting for the spark plug hole to pressurize the cylinders in order to keep the valves from falling when you remove the valve keepers. You would need a on the car valve spring compressor to compress the springs so you can remove the keepers.
I don't think you will need springs though and should look more towards the lifters. If not done properly though you can damage the valvetrain.
Use the Sea Foam through the brake booster line pouring it in slowly while keeping the engine running. Does not have to maintain 3000 rpm but you have to keep it running. Pour a little and let the engine draw it in.
Also pick up an engine flush. I like the Amsoil brand but you can only get it online and at authorized distributers. Not sure if you would have any in your area. Use a name brand and follow the instructions. Make sure it states that it helps free sticking lifters.
Changing out the lifters is just a matter of replacing the rocker arms. The rocker arms contain the lifters in the ends of them and are an integral part. To change the lifter is to change the whole rocker arm. The rocker arms can be purchased through NAPA and run around 40.00 each. There are different ones for different cylinders. There are 4 intake front, 4 intake rear , 2 exhaust for cylinders 1 and 3 and 2 exhaust for cylinders 2 and 4. They are different and must go in the right places.
You can replace just the ones making noise if you can find the ones that compress easily by pushing down on them. Harder to tell if you have never felt for play in them before. Good ones will be stiff and have alot of resistance, bad ones will compress by pushing down on the round end without much resistance.
B - 12 chem should be fine. If you want to attempt the rocker replacement the procedure is below. Have a close look at it to see if you want to try it. This is rocker shaft replacement since the shaft must be removed to change out the rockers. You would just install the new rockers when you reach the install components part.
2.4L 4-CYL -1996 Nissan Pickup Page 1 of 2
ROCKER ARM SHAFT ASSEMBLY
CAUTION:Rocker arm contains integral hydraulic lifter. DO NOT lay rocker arm on its side unless submerged in oil.
Removal & Disassembly
1.Disconnect negative battery cable. Remove cylinder head cover. Position cylinder No. 1 at TDC of compression stroke, ensuring camshaft knockpin (or keyway) is at 12 o'clock position. See Fig. 7 . Ensure marks on crankshaft pulley and front cover are aligned. 2.If camshaft is to be removed, measure and record camshaft end play. Support timing chain with Chain Support (KV10105800). See Fig. 5 . While preventing camshaft from rotating, remove camshaft sprocket bolt. Remove camshaft sprocket. 3.Loosen rocker arm shaft bolts evenly in 2 or 3 steps, starting with outside bolts and working inward. Remove rocker arm shaft assembly and bolts. Mark component locations for reassembly reference. Remove components from rocker arm shafts.
Inspection
See VALVE TRAIN under OVERHAUL.
NOTE: Intake rocker arm shaft has one punch mark at timing chain end. Exhaust rocker arm shaft has 2 punch marks at timing chain end. Install both shafts so punch marks face upward. See Fig. 9 .
Reassembly & Installation
1.Ensure camshaft knockpin is at 12 o'clock position (cylinder No. 1 at TDC of compression stroke). See Fig. 7 . Assemble rocker arm shaft with components in original locations. Install rocker arm shaft assembly onto alignment dowel pin of cylinder head. 2.Gradually tighten bolts to specification in 2 or 3 steps, starting at center and working outward. See TORQUE SPECIFICATIONS . Set timing chain on camshaft sprocket, ensuring mating marks align. See Fig. 7 . 3.Install camshaft sprocket, and tighten bolt to specification. Remove chain support. With rocker arm in free position (valves closed), press downward on rocker arm, at valve end of arm. If rocker arm moves more than .04" (1 mm), air may be inside lifter. See BLEEDING LIFTERS procedure.
4.Apply sealant to rubber plugs and cylinder head half-rounds. See Fig. 4 . Install rubber plugs. Wipe off excess sealant. Install cylinder head cover. Tighten bolts to specification. Connect negative battery cable.
Bleeding Lifters
Operate engine at 1000 RPM under no load for about 20 minutes. If lifters are still noisy, replace lifters and bleed again.
Fig. 9: Installing Rocker Arm Shaft Assembly Courtesy of NISSAN MOTOR CO., U.S.A.