2000 Nissan Altima Misfire

Hi! First time poster here. I have a 2000 Altima SE w/ 2.5 4cyl. I have a misfire in cylinder 4. My mechanic has looked at it and switched my fuel injectors and ruled that out. I’ve given it a tune up and that didn’t work. Does anyone have any experience with stubborn misfires in this model? It has a lot of miles and it needs a clutch, but I’d like to fix it if I can.

What did your tune-up entail? Were plugs, plug wires, and/or distributor replaced?
Sounds like you have eliminated the fuel side of the equation?

Plugs, wires, & cap (Is it a cap? Whatever rotates and creates a complete circuit for each wire. I always forget what it’s called). My mechanic switched the injector for the 4th with the 2nd and then the 4th with the 3rd and it still stayed in the 4th cylinder. No rot on the knock sensor harness. I’m at a loss.

Have your shop check the compression. Before you go on a wild goose chase you want to rule out a mechanical fault. (To fire the cylinders need fuel + air compressed - and then spark).

Sorry forgot to mention that too. They checked that and it held it 150psi. My car did overheat last summer and they checked the cooling system and it held pressure too.

One thing that is left - though I’m sure there are more things - is the wiring harness for the injectors -intermittent connection?

I assume, btw, that the code you have is P0304 and that is the only one. If that is incorrect or there are more, then report them.

Another thing to worry about is the PCM (computer) itself.

Last thing to mention is my car has 220000 miles on it and will need a clutch too. I don’t know the code, but I could definitely look at the harness for the injectors myself. My mechanic put a bunch of time into it and didn’t charge me for it and I didn’t want to pour a bunch of diagnostic time into a car. How hard and costly is it to replace a computer?

220,000 miles on it?

If everything else has been ruled out, cylinder #4 may have excess carbon build-up on the intake valve. This carbon build-up can effect the fuel injector from properly delivering fuel to that cylinder. And this can cause a misfire.

Ask your mechanic if he knows how to decarbonize an engine using Seafoam.


2000 Altima GLE Automatic
JUST started this “Service Engine Soon” light thing after an oil change around Thanksgiving.

Replaced O2 sensor
Replaced Plugs, wires, Dist Cap and Rotor
They even replaced the #4 Cyl injector.
Checked for head gasket, intake manifold gasket leaks.
Yet STILL I get an engine light.
The bizarre thing is that the light would go OUT on it’s own, too. Sometimes - usually when I brought it in for service.

That carbon fouling thing makes me wonder. I spent several years idling at the T station to stay warm/cool.
The idle is really bad. Like someone who had too many warm Molson beers and egg salad sandwiches. Puh, puh, puh out the tail pipe, if ya know what I mean…

Still no resolution, but I have a rental ($) and they noticed excess fuel (‘soaking wet’)and are doing other things. Perhaps tomorrow.

BTW, it only has almost 52,000 miles. Again, all that idling, and now heavy traffic into Quincy MA.

Oh, and if you are thinking about a 2009 Dodge Caliber SXT, I hope you like driving with your head in a big pipe. Absolutely NO visibility, and the front head rests are bigger than a real head! NOT going on my list.



Check out the intake manifold gasket. They seem to have a history of leaking on this car, and would cause this sort of problem.

A 150 PSI is dropping but should be sufficient to run at least decent.
Something simple you could do is use a stethoscope or long handled screwdriver and listen to the injector on that cylinder. You should hear a steady, faint clicking sound.

What are the symptoms of this misifire; rough idle, bucking and jerking at speed, etc.?

If the compression is really that good, the injector is pulsing as it should, and with new plugs, wires, etc. and IF the symptom is a rough idle only that smooths out off-idle then you might consider a valve lifter problem or a weak valve spring.
A vacuum gauge connected to an intake manifold vacuum line would reveal something like this very quickly as it would a manifold vacuum leak.

I have one of these. They have a faulty gasket that causes cylinder four to misfire after 150,000 miles or more. I bought mine and immediately had it fixed for $400. Solved the problem immediately.

Hi guys. My name is Vincent and I also am having a multiple misfire issue with my 2000 Nissan Altima. Have tried everything possible and the check engine soon light goes off and on. Did notice that whenever I put gas in it it starts to act up. Although the car runs just fine. Only has 75,000 original miles on it. Any help resolving this problem would be greatly appreciated. Thanks