my mechanic is stump have a 1997 Nissan pickup 2.4 liter auto tranny. number 2 cylinder misfiring.my mechanic say it have fuel, spark. and he did a compession check say compression is good. code (p. o 302) keep coming on. he change spark plug and wire and distributor cap and rotor. but light keep coming on. he say the only other thing he can think may be is. to change the hole distributor he say the cam sensor is in the distributor. tuck have 264,000 mile on it.
What are the compression numbers? Those should be written down. The reason I ask is because many times those numbers are not as good as they should be. Even many service manuals have erroneous figures on this and some mechanics buy into those specs.
At 264k miles those numbers could be suspect. The compression ratio is about 9 to 1 and the rule of thumb on an engine in good mechanical condition is 20 X the compression ratio; about 180. Allowing for wear and decent compression it should still be in the 150 or better range.
If the compression is at least acceptable and spark is good then a faulty fuel injector, fuel injector wire circuit, or ECM fault is the next thing to check out. After that the odder things such as a weak valve spring, air leak into an intake duct, etc come into play. Hope that helps.
Another trick is to swap the #2 injector into a different cylinder. If the misfire code follows the injector to the other cylinder, the injector or its electrical circuit is causing the misfire.
I think you should start by getting a new mechanic. It sounds like he/she is lacking in mechanical troubleshooting skills.
Misfire, that means the computer isn’t detecting the crankshaft getting a boost of power at the time number 2 should be firing. For that boost of power to happen there has to be spark, gas injected, air in & exhaust out, and compression. Since it is only happening on one cylinder, it has to be something unique to that cylinder, so it is unlikely to be the distributor or the cam sensor, b/c those parts are used in the same way on the other cylinders.
So think about it like Sherlock Holmes would, after considering what you’ve already done.
What about air & exhaust? The only thing that is different on 2 vs the others is the intake & exhaust valve, disproved by measuring the intake & exhaust valves’ clearance on number 2.
What about spark? The shop should have an ignition analyzer instrument to test if the spark on number 2 is any different than on 1,3, & 4. The shop should be able to show you the display of the 4 spark waveforms so you can see for yourself. If they can’t, go to a different shop.
That pretty much leaves fuel. As @jesmed1 recommends, an excellent way to disprove fuel supply as the cause is to switch injector 2 w/injector 3 (say), then see if the problem goes to number 3. If it does, you know you’ve got an injector problem.
The other fuel explanation is the electrical pulse that is supposed to fire the injector isn’t getting to the injector. The first step is to remove the connector to that injector and give it a good look-see. Everything look ok? Good shops have special probes and instrumentation that can prove/disprove this. Again, if you shop doesn’t have this level of basic diagnostic instrumentation, go to a different shop.
Had a misfire on a 2000 Focus @ around 90K,the code said left bank lean,replaced the cheap injectors,ran like new ,till it dropped a valve a few thousand miles later.