I have 2006 nissan altima 2.5S. Service engine light is on… shows P0301 code (cylinder 1 misfire). I already changed the Ignition coil and spark plugs… Car still shakes when apply brake.
Please advice.
Have someone check if the brake rotors are warped.
Tester
Clarify symptom : vehicle shakes when stopping with brake or vehicle shakes when stationary with brakes applied.
shakes when apply brake and stop at red light. Also, when reaches the speed of 70km/hr… starts shaking. When neutral… no shaking problem.
Does it shake after you’ve stopped at the red light, or as you slow down approaching the red light with the brakes on? The reason I ask is b/c if it is the latter, that’s a problem with the brakes, likely warped rotors. If it shakes while you wait at the stop light with the brakes applied, that’s more likely a problem with the power brake booster. That could also be caused by the misfires you are experiencing, if it only occurs in D with the brakes on stopped at a red light, but doesn’t when you shift to neutral independent of the brakes applied or not.
You need to have this vehicle inspected now. Before you kill yourself or others.
What you’re describing is a problem with the steering/suspension.
If you can’t figure out what he problem is, bring it to somebody who can.
Tester
I suspect that you have two problems.
The Check Engine Light and code is a totally different problem than the shaking when you’re stopping. The shaking at 70km/hr speeds could be from either source.
I think you need to first have the brakes checked. You may have a warped rotor, and it may be time for a brake job. Have them take a look-see too for anything else that might cause shaking at moderate speeds.
By the way, how many kilometers has it been since the last brake job? How many kilometers does the car have on it?
The cylinder 1 misfire… you started out with the basics, now you have to get the actual cause diagnosed. It may be a bad injector or some other cause that would isolate its manifestations to only one cylinder. A shop will have the ability to isolate the cause. If it’s a high mileage engine, a compression problem is even a possibility.
If the car has ABS it could be that feature. Some of these systems cause chatter when applying the brakes firmly. Try it with the ABS off, if possible to see if there is any difference.
how did plug look when you took it out? black? white? how did it compare to other plugs? coil swap is easy. if you idle motor and unplug coils, one at a time does idle change for each? should be real apparent with 4cyl
Today, I went to a mechanic. He took all the coils and spark plugs and swap each other. Also, he also took out the plug associated with each coil one by one. All seems to be OK.
Compression test is fine too. He erased the code and ask me to drive for few kms.
After driving for 38 kms , the engine light again comes. with the same code. P0301.
Please define “fine” . . . did you get any numbers?
So . . . no parts were actually replaced, only moved around?
I would suggest finding a mechanic who is willing to perform more extensive diagnosis
Could be lots of things, for example a fuel problem
thought you said cyl 1 had new coil? why would he touch cyl 2-3-4 parts?
First I change the Coil and spark plug for cylinder #1 and erase the code. After driving for 15 kms , the engine light comes again.
Then I did the compression test and switch all the coils and spark plug and erase the same code to verify the situation. After driving 37 km the engine light came again with the same code.
Even check the ECM and it seems to be OK. No fault.
But car still shakes and light is ON.
Try clearing the code, swapping the #1 injector around with another, and see if the cylinder identified by the code follows the injector.
Swapping the plugs and coils around to see if the misfire goes with the swap or not is the standard way of diagnosing that problem. If after doing that the code changed to 0302, and 1 and 2 cylinders had been swapped, the shop would know the problem is with one of those parts. But you still know more now than before. You now know the problem isn’t the plugs or the coils. And it isn’t a compression problem.
There’s other things that can cause a misfire on cylinder 1 that need to be tested now.
- Is the number 1 injector being pulsed by the computer the same pulse duration as the number 2 injector?
- Is the number 1 injector faulty? Swapping number 1 and 2 injectors would show that one way or another.
- Is the valve clearance on number 1 in spec, and the same as the others (in spec or not) for all the other valves?
Any fuel rail removal requires new O-rings per FSM guide.
It is inline-4 engine, if removing injectors, it would make sense to thoughtfully clean them all in the same time as performing 1/2 swap: this way the spray pattern can be visually tested before and after cleaning, then if problem follows the injector, then it is clear indication for replacement, if proboem disappear, then dirt in 1st injector was a root cause.
Given the cost, the easiest would be to buy remanufactured injectors like next set and simply swap:
https://www.ebay.com/itm/4pc-Fuel-Injector-For-Nissan-Altima-Sentra-2-5L-2500CC-2003-2006-195500-4390/331991017210?hash=item4d4c34e6fa:g:eD0AAOSw4shX9P6X&vxp=mtr
I found it easy to refurb on my own, even with basic tools. Something like this will do:
https://www.ebay.com/itm/2002-2006-Fuel-Injector-Repair-Service-Kit-Seals-Filt-for-ALTIMA-SENTRA-2-5/152258344716?hash=item23734df70c:g:hV8AAOSwHHFY9pqM:sc:USPSFirstClass!20165!US!-1&vxp=mtr
Aren’t you getting a little ahead of yourself?
It has not been proven that the injectors are the cause of the misfire
There’s still more testing to be done
It could be a wiring problem . . . rodent damage is just one example
As has been mentioned many times on this forum, the shotgun approach is very often costlier than a proper diagnosis and repair
I do agree I tend to jump the gun, when it is in “under $50” range and is generally in benefit to the end-result.
Anyway, swapping injectors 1/2 will require them to pull the rail, which will require to replace O-rings, which are $3-5 a piece from the dealer, so getting a full set (including mesh filters) for $15 and making “let’s clean it up and see if it helps” would immediately be on my list, “just because”
As I said before, I’ve run into lots of situations where the customer has replaced this, swapped this around, repaired this, etc., and the problem STILL persists. So they’re already out a lot of money, and faced with paying for a proper diagnosis and repair. And they’re often not very happy, when you tell them that none of those parts needed to be replaced, that they in fact weren’t even on the right track
I’m coming at things from a different perspective, and I suspect we won’t see eye to eye on this one 
Must you tell them? Can you not simply fix the vehicle and give them the bill? They’ll figure it out themselves.