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1999 nissan altima- engine pops and backfires into the manifold-Why

The car crank up normally, but when idling it misfires on #3 cylinder. When start to drive it will drive at 45 mph at full revolution but when I stop at a light the engine begins to vibrate and shakes the entire car. When moving off again, it continues to vibrate and hesitate and will not get up back in speed 25-30 mlp and now start to backfire in to the manifold. While stepping on the gas it also makes a popping sound. If I try to get the speed up any higher it will violently makes a popping sound and backfiring constantly into the manifold and struggles to go. The engine is also getting very hot although the engine gage said it normal and not overheating. If the car is sitting in a grassy area while idling it will completely burn dry the grass underneath. Can you please help me with any advice. Thanks

Sounds like your cat may be plugged. Also, bad coil, injector or plug on 3.

This can be caused by a few things… You could be in Dire need of a Tune up…OR more likely…It sounds like your TIMING IS WAY OFF…This can be from a Stretched timing CHAIN if you have a lot of mileage on this engine… It could also have Jumped Time, again from the chain being stretched. You need to go thru the procedure for setting the timing on your engine and see where you are now with the timing setting…and adjust accordingly.

You need to know what you are doing with this one. I would start with the timing first just to see where it is now in accordance to the timing setting. You also CANNOT ignore the state of the engine tune up parts…Had it ever had a tune up? Plugs, wires, Distributor cap and rotor…etc?

Did the vehicle run perfectly shortly before all this happened? Did this condition happen suddenly? ASSUMING THAT you are not in SEVERE need of a tune-up…I would look at that timing

Let us know what you see after you put a timing light on the motor…where is the timing set now? You should be able to tell us after using the timing light. Let us know what you get… As I said several things could contribute to these symptoms…Was it running perfectly just prior to this? Did this happen suddenly? Etc… all things that need answers. Let us know so we can help further.


The misfire in cylinder #3 means the gas in that cylinder is not being burned properly. The gas gets exhausted into the exhaust manifold, then gets heated by exhaust from other cylinders, and burns, causing the backfire.

Some unburned gas continues into the catalytic converter, where it causes the catalytic converter to overheat and start the grass fires under the car.

You must have this fixed immediately or it will damage the catalytic converter, which is very expensive to replace. As knfenimore said, the catalytic converter may already be plugged, which could be the cause of the misfire. But don’t replace the catalytic converter except as a last resort, since it may not be the cause.

Heads up . . .

I believe OP actually has 2 threads going for the exact same car and problem

I’ve seen burnt or sticking intake valves cause backfiring into the intake manifold under a load. A compression test would reveal this.

I’d leave it as it is.
Park in one spot on the larn today and move it every day.

No more mowing!!!


+1 to9 Honda Blackbird’s post.

The first thing that came to my mind too was valve timing. This has all the signs of a jumped chain.

And, as already mentioned, the more you can tell us about the history of the car, especially the very recent history, the better we can help you.

There’s a number of reasons why cylinder No. 3 could be misfiring assuming that diagnosis is correct. Spark plug, coil, low compression, etc, etc.

It could also be that the converter is clogged or ruined and running hotter due to an existing problem so I STRONGLY urge you to keep that car off of any grass. Continuing to do so is begging for trouble.

Just a couple of years ago here in OK a state trooper was chasing a fleeing suspect who bailed out and took off running across a field. The trooper slammed his cruiser to a halt out in the field and took off after the guy.
He caught the suspect but in the interim the hot catalytic converter set the weeds on fire and burned the cruiser to the ground; and his car was running normal.

An overheating converter has also been known to set interior carpet smoldering or afire.
My gut feeling is that this car is going to need a number of things with no single magic bullet fixing it.

As always, excellent advice from OK4450. When cat converters first came out, there were chronic problems with grass fires. The temperature of a burning match generally ranges from about 600F to about 750F. Cat converters can exceed 800F, clogged ones even higher. Heat shields were added to alleviate the problem, but in your case your car is clearly able to start a fire.

Please, avoid parking on grass until you can address the problem(s). You could turn an operating problem into a huge fire.

Thanks you guys for all of your input. I agree this is not a quick fix and we are starting to eliminate as we go. The problem that is puzzling is the car runs good and only start to break down when it starts to get hot about 15 minutes into driving. This car started giving problems with the same symptoms of not getting up to speed about 4 months ago and we changed the fuel pump n the distributor and then it worked find until it started happening again. Those parts that we changed are working and not showing anything wrong. we are not going to check the cat converter. How many cat converters are on my 1999 nissan altima and where is it located?

sorry, now going to check the cat converter.

You can disconnect the cat and see if it helps the problem. Rapping on the cat and it rattles inside means it’s bad.