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Category: Nissan
Satisfied Customers: 26451
Experience:  ASE certified tech ADVANCED LEVEL PERFORMANCE. Wisconsin certified emissions state inspector
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2000 Nissan Altima: idle, P0304 code (4th cyl misfire)..ran great

Customer Question

2000 Nissan Altima 102K. Shudders at idle, P0304 code (4th cyl misfire). Similar problem/code 5 months ago, replaced intake manifold gasket, then ran great. Now same problem, except overheats quick and bubbles seen in coolant resevoir. Mechanic suspects head gasket, but does not seem sure. Any other ideas? Expected cost? Thanks.
Submitted: 8 years ago.
Category: Nissan
Expert:  AMEDEE replied 8 years ago.
Hello there!

When was the last time the engine was tuned up? No, not just plugs, but a full tune up! The whole nine yards! Any part of the secondary ignition will do this including the ignition coil or coils! This sounds like a classic ignition misfire! They usually go bad under a load like under acceleration, but can be noticeable at any time. It is very important to have your engine equipped with good tune up parts or you may be causing damage to other components of you car like the catalytic converter which can be expensive!

Possible causes:

Ignition misfire causes by any bad tune up part and or ignition coil or coils.
Bad spark plugs, spark plug wires and cap and rotor (if equipped)
Wrong tune up parts spark plug, wires etc...

The quickest way to check the ignition components, is by looking closely for leaking secondary voltage. Visual look at all the tune up parts to see if you can see any sparks coming from any of the wires or coil (or coils) when the vehicle is running. If not, you can put your hand on the coil/coils and wires when the engine is running and see if you feel any small voltage leaking form the tune up parts.

It will leak secondary ignition voltage from the tune up parts caused by high resistance from carbon tracking if they are bad. This is very common if the tune up parts are not changed regularly!

If any is found, the tune up parts are simply bad and will need to be replaced! If none is found than you can spray a mist of water on the tune up parts when the engine is running and see if that causes the engine to stumble or run rough at all. Again, if it does, the tune up parts are bad and will need to be replaced!
Customer: replied 8 years ago.
I changed plugs, wires, rotor, and distributor cap at 92,000 before I realized the intake manifold gasket was the issue. All parts were proper and it has runn smoorthly for the last 6 months since tune up and gasket replacement. I do not think this is the problem.
Expert:  AMEDEE replied 8 years ago.
I dont think this is your problem either.

You just asked for other ideas.

This could be one.
Customer: replied 8 years ago.
So, do you think it is the head gasket? Or could it be the intake manifold gasket again, just worse (since I used an aftermarket gasket)? Are there certain tests I should make sure my mechanic runs, since I cannot handle this one myself? Thanks.
Expert:  AMEDEE replied 8 years ago.
If the problem is only at idle, it could be a intake manifold gasket causing your misfire if the vacuum leak is big enough.

But if it is always misfiring on that cylinder, an e rad test will need to be done. This test will verify if there is any emissions in the radiator. If there is, the head gasket is blown and will need to be replaced.
Customer: replied 8 years ago.
What is a reasonable expectation for head gasket replacement cost? My mechanic says $1200. I expected $900 by Alldata estimate of time and parts and local labor rates.
Expert:  AMEDEE replied 8 years ago.

Well ALLDATA might not include resurfacing the head.


ALso, there are things that happen during the repair. Small hoses may break, the mechanic might be charing you for the new coolant he is going to be putting in your engine, plus new oil... and the list goes on.


If you want, you may shop around to get a better price, but 1200 for this repair does not sound unreasonable if it is a head gasket.


Try spraying some starting fluid along the intake gasket and see if the idle changes. If so, this vacuum leak is big enough to set this p0304. If this does effect the idle, I would replace the intake gasket before replacing the head gasket. Unless of coarse, there are a tremendous amount of bubbles consistently coming form the coolant in the radiator. Then My money would be the head gasket. Just be sure to have the mechanic run the correct tests before replacing the head gasket just to be sure.

Customer: replied 8 years ago.
Before taking it to the mechanic, I tried spraying carb cleaner around the intake gasket at the 4th cylinder. No change in idle. (This was a positive test when the intake manifold gasket blew in April giving the same code.) There is a lot of bubbling in the coolant resevoir this time-which has never occurred before. Mechanic tells me for sure it is the head gasket now. He pressurized the radiator a little at idle and caused white smoke to come out the tailpipe. Also tested oil and found a trace of coolant. Seems so far that nothing else was damaged when it blew. This all happened very fast. Rough idle, bubbling in coolant resevoir. I tried not to drive it until my appt, then it started overheating on the way to the shop-had to stop on the way. He also thinks the temp sensor is bad. It registers hot after moments of engine running - unsure how that fits into the picture. Any idea? As for the cost, he would charge extra if resurfacing needed ($60), but he was reasonable with the other job he did for me, right on what I would expect, so I'll trust him on it. Not an easy engine to work on. Just hurts to spend so much. Thanks.
Expert:  AMEDEE replied 8 years ago.

THat is correct. These motors are very good but very hard to work on.


I would say with that bit of extra info that you just gave me, that the head gasket is for sure your problem.


The temp sensor very well could be bad. But in fact if the head gasket is really bad, (which it sounds like it is), then it would pump air pockets into the cooling system causing erratic temp readings. Just a thought.

AMEDEE and other Nissan Specialists are ready to help you
Customer: replied 8 years ago.
Thanks for your help.
Expert:  AMEDEE replied 8 years ago.
Thanks for the accept!

Good luck!