TwinTurbo–I took it to 3 different shops (referrals from the previous one when they couldn’t discover the problem). One of them (an import mechanic since it is a nissan) checked the combustion on it–I watched him check–& it was combusting. The last mechanic that looked at it works in a shop, as well as is opening his own (done mechanic work for 20+ years) & he spent 5 hours checking every connection he could find leading to cylinder 6. Checked the wires connecting to the coil, he spent an entire afternoon checking things. Found nothing & sent it home with me. The next day after doing some research * talking with other mechanics he works with, they found that a timing chain could cause misfiring.
It originally had cylinder 4 misfiring, changed the coil & it worked. Then it said there was a random misfire, replaced plugs (for the 3rd time in 6 months) & it went to misfire on cylinder 6.
Cougar–Would those lines be ones that are connected into the coil pack? If so those were tested & had the correct voltage…
It’s not possible to observe normal combustion on a cylinder that is misfiring. If in fact the combustion is normal on number 6 like your mechanic says, then the check engine light must be in error.
Think about it this way. For normal combustion to occur, and not create a misfire, you have to have the following
air into the cylinder
fuel into the cylinder
compression to appx 140 -180 pounds per square inch
spark, at the proper point in the cycle
exhaust gas completely swept out during the exhaust stroke
If your mechanic is correct, than all that is happening correctly. And it is pretty simple for an experienced mechanic to verify all those, although it can be somewhat time consuming. If all that is correct, and you don’t notice anything wrong when driving the car, the only reason for the misfire code must be that the ECM is making an error, thinking there’s a misfire, when there isn’t. So what could cause that? Maybe it is confused where the crank or cams are positioned, so that would mean possible bad crank and/or cam sensors. Or the PCM itself could be bad.
It would be helpful to know what the compression numbers were whgen the mechanic tested the compression.
Was a leakdown test performed. That should indicate if it is a bad ring lowering the compression, or a bad valve, causing the misfire.
Timing is not the issue, because more than one cylinder would show a misfire.
The other question is. The mechanic that said it was combusting ok…how did he test this???
Another important part. One guy spent 5 hours testing the wiring to cylinder 6.
That must be a record 5 hours for three wires.
I think he took too many beer breaks or naps to spend that much time and find nothing.
the mechanic didn’t just check the wires to cylinder 6, he checked over everything he could think of that could even remotely possibly cause it to misfire.
It has been over 2 weeks since they tested the compression, so I don’t remember the numbers.
I am wondering if all of the wires tested correctly, if it could possibly be the piece that connects to the ignition coil.
I am wondering if all of the wires tested correctly, if it could possibly be the piece that connects to the ignition coil
If the wiring were incorrect, then it would misfire. If the mechanic says it is not misfiring, then the wiring is correct. I presume your mechanic engaged in the process any mechanic would do in a case like this, check for loose connections in the wiring going to number 6, b/c that could cause a misfire that wouldn’t occur in the shop, only driving down the road and going over bumps or turning. Since he spent 5 hours, doubtless this has already been done.
The next day after doing some research * talking with other mechanics he works with, they found that a timing chain could cause misfiring
This is ludicrous. What mechanic has to ask his peers something like this?
You keep defending these guys as experts and yet there is proof here they don’t know their butt from a hole in the ground. Either that or you have completely skewed the information. Until you realize this, no one here can help you.
5 hours checking the wiring for a single cylinder…hook up a noid light and see if it flashes. Trace it back. should take 20 minutes. Diagnosis 101…
Yes the wiring was checked. The wires were found to be working correctly & were not loose. Hence, since the power stops at the ignition coil (yet the coil works on other cylinders) the reason I am wondering if the connector could be bad.
@TwinTurbo – amazing how you expect every mechanic to know everything, yet everything you have suggested has been tried or tested & we can still not find the reason for the misfire. Glad you are intelligent enough to have figured it out (but not with my car). I am a teacher, & still KNOW that not everyone can retain the information necessary for EVERY car.
Everyone else thank you for your assistance. This is a VERY trying time–trying to figure out what is wrong, so thank you for not placing blame.
You have been getting conflicting information from your mechanic(s). I don’t know if this is caused by an intermittent misfire or if it a communication problem between your mechanic to you to us. Without seeing and testing the car, there is no way for someone on the internet to tell what is wrong.
I do know that on this vintage Maxima a misfire that survives replacement of coils and plugs and isn;t a compression problem is usually caused by fuel injectors.
@Nevada_545 – the wires have been tested leading to the ignition coil & came back fine. the ignition coil can be put on another cylinder & fires fine, but not when attached to the piece going into the ignition coil for 6.
@“oldtimer 11” --thank you that is helpful to know, because the compression is good & it has new coils. I appreciate your knowledge.
I think there’s some communication ambiguity problem here. It appears the mechanic isn’t saying it’s not misfiring, just that he can’t figure out why there is no fire on number 6. And it’s even more focused than that, it seems to be traced to a no-spark problem on number 6.
hmmm … well, for a spark to be produced the igniter has to send a current pulse to the coil, and the coil must have a relatively low ohm connection to the igniter, and to ground. I wonder if the problem is that the coil ground isn’t securely connected.
OP, there’s usually an assortment of ground wires running between the engine and the chassis. It’s worth double checking all of those are in place and connect the engine to the chassis with a good solid connection. On my Corolla one of those wires has a connector in it, and sometimes I need to disconnect that connector to access something, and will forget to connect it back up again. When that happens, once I start the car the CEL turns on and the engine runs poorly.
I am a teacher, & still KNOW that not everyone can retain the information necessary for EVERY car.
Well, that speaks volumes. If you had been paying attention, you should have grasped by now that these systems are fairly common to ALL cars. It’s not far from saying my tire has a leak but they can’t figure it out and your defense is how can they know how every tire works…
Many people have tried to educate you on the problem but it hasn’t appeared to sink in.
You still haven’t clarified for people trying to help you some basic contradictions in your posts:
Now to find out why cylinder 6b has no fire
-they are all combusting normally
amazing how you expect every mechanic to know everything
Some things are basic. Your recollection is that mechanics have told you a timing chain can cause single cylinder misfires, the ignition switch might be the cause and a number of other ludicrous suggestions no mechanic worth anything would suggest. There is one common thread in the diagnostic process to consider. I’ll leave that for you to figure out…it’s your dime.
Please don’t take this the wrong way, but I simply do not believe that any of your mechanics checked to see if your cylinders “are combusting normally”
I believe one or more of your mechanics checked compression
It would be nice to have some more information . . .
Dry compression numbers for all cylinders
Wet compression numbers for all cylinders
With all due respect, I have the feeling you’re trying to use the words combustion and compression, as if they’re interchangeable
@db4690 If I understood what was told to me, the combustion is the pressure from the fuel injectors. & the compression is from the ignition coil? They are different, I may have confused where each came from, but understand they are different.
They did not tell me wet or dry compression numbers.
No, sorry, that is totally wrong, both of your understandings.
Combustion is the process where the fuel and air is burned, ignited, in the cylinders to produce power.
Compression is the pistons compressing the air-fuel mixture before it is ignited. Compression is measured as the amount of pressure when the cylinder compresses just air. A low compression means the cylinder is leaking, either via the valves or the rings.
