help!

I took my car into my local mechanic with the check engine light on and degraded performance. He looked at the code which said misfire. We replaced the spark plugs which did not clear the check engine light. He looked everything over, took apart the cylinders, then thought maybe it was the fuel injector but then finally said it was an ECU problem. how likely is it an ECU problem? He says its running on 5 cylinders and could damage the cat. Could it be a fuse or relay issue instead? I dont drive the car hard at all, so find it hard to believe the ecu would fry? The car is still running on 5 cylinders and everything else works fine. I'm a car noob so any advice or experience would be helpful at this point.

 

Find a new shop

 

+1 to the new shop and get a 2nd(now 3rd) opinion..

 

what else would cause a cylinder not to fire?

 

Your ECU is fine. You could drive the **** out of your car, and it's not going to "fry" the ECU.

Many things could cause you to be misfiring.
-Bad spark plugs (if you replaced them all, then that's not the problem)
-Bad ignition coil, or coils (thing that sits on top of spark plug)
-Bad electrical connection to ignition coil (maybe a wire fell out of the connector - unlikely, but easy to check for)
-Fuel injectors stuck open causing car to run excessively rich (too much fuel)
-Fuel injector o-ring leaking excessive fuel into combustion chamber
-Vacuum leak (not enough air getting to combustion chamber)
-Lack of compression (could be caused by blown head-gasket, failed piston rings)

What is the mileage on the car? What year? There are common problems with these motors that you should check for, especially on the early 2003 VQ35DE engines.

Also, don't worry about damaging the catalytic converter too much. If you're in a state where you have to SMOG your car, this might be important to you though. As long as your car isn't blowing smoke out of the exhaust, I wouldn't be too worried about your problem.

Oh, and +1 on getting a new mechanic.

 

Mcarther I believe a vacuum leak would cause a "system too lean at idle" fault which would be too much air in the combustion chamber and misfire on multiple cylinders. or in my mechanical experience at least lol.

OP just like mcarther asked, what's the year and mileage of the car? oh and definitely go to a different shop, i'm sure its as simple as a bad coil.
You say youre a car noob so I cant really tell you to try something but it would be a good learning experience.

If youre up for it do this, its rather simple for a car noob
With a scan tool find which cylinder is misfiring. As an example lets use cyl 6, take the coil pack off cyl6 and swap with cyl5, or any other one , it doesn't matter.
Next step is to see if the missfire is still on cyl6 or not, if the misfire moved to cyl 5 or which ever coilpack you swapped it with then you have a bad coil pack.

 

I wanted to give an update to my car. Based on the feedback, I took it to another shop and they diagnosed it as a bad fuel injector and the cost for the part is $175. Does that sound high? I know autozone sells them from $60-$120. Anyhow, thanks for the suggestion to go to another shop I really appreciate it!

 

I was thinking bad coil pack also.

 

Swap coil packs between a good/bad cyl and see if the misfire follows. You can tell which cyl is misfiring by disconnecting one coil pack at a time... if the engine RPM/sound doesn't change on one of them that's your bad cyl.

 

The new shop replaced the fuel injector but again it did no fire, so the prognosis was it needs a new ecu.. uggg.

 

What about the coilpack like everyone's suggesting?

 

I'm assuming the last 2 shops tested the coilpacks and determined that wasn't the cause of the problem. In the end, Both shops confirmed it was the ECU unit. I have a 2004 350z with 90k. I still have a hard time believing its the ECU unit!