Yes, it’s a possibility, but there are other possibilities that result in these symptoms, even though they affect the ECU in ways that make it appear that the ECU is the problem. One of those possibilities that hasn’t been mentioned is a failed Engine Coolant Temperature Sensor. These are simple thermistors that the ECU relies on to trim the air:fuel mixture correctly. A failed ECT sensor would cause the ECU to enrichen the fuel and cause hard starts and bad combustion, accompanied by shaking. On a Nissan, a new OEM coolant temp sensor is about $30 and takes about 2 minutes to swap. Hope that’s all it is.
I just came back from the dealer. They couldn’t find anything wrong with the car! The mechanic said it could be because of bad fuel. When I said I live about a mile from work, the mechanic recommended I allow the car to warm up in cold weather. Most of the times the problem did happen during cold weather and first thing in the morning, so this seems to be a sensible thought process…do you folks agree?
If the problem reappears, they want me to get it checked again; then they said they’d have to do some compression tests (on cylinders?) and look into it in detail. 
All engines misfire, even well tuned ones. Then, it would be an occasional misfire. An engine that has more misfires, will have a rough idle, or feel rough at higher rpm. An engine that has noticeable misfire, is actually having multiple misfires. These are the misfires, especially, which will turn the check engine light on and set a code. A rough running engine may, also.
Actions to take: change the spark plugs, and drive a few days. If the CEL comes on, again, swap ignition coils. Drive a few days; then, if the CEL, still, comes on, the rest of the ignition (spark system) needs dedicated troubleshooting.
No I don’t agree at all with the bad gas diagnosis or a compression problem. Either one would be present all of the time if that were the cause; with a few rare exceptions. Bad gas is a hokey diagnosis 99% of the time.
As I suggested earlier, I would replace the plugs as a first step and replace the coil on the faulty cylinder as a second step if needed.
When a coil provides a spark that spark is going to attempt to go somewhere. It should go across the tip of the spark plug. If it cannot, then it’s going to go through the side of the plug boot (part of the coil) and into the cylinder head or valve cover. Replace the faulty plug and the spark will then take the easiest path; the plug gap.
Plugs can misfire when cold, straighten out when hot, and it can also work in the reverse along with random misfiring at any time.
If the plugs have never been replaced in 86k miles of short hop driving then why in the world have they not recommended this? Lord.
My car is in ICU now! Please help!
In the last few months, the misfire problem surfaced several times and went away without a discernable pattern, but I took it to a mechanic anyway about a couple of months ago. He swapped the coils to see which cylinder was creating the problem, but then it had multiple misfires after that. Then he changed the spark plugs. The problem went away until a couple of days ago when it was misfiring horribly and the car was barely moving.
I had the car towed to the mechanic this morning. He called me a couple of hours ago and said all 4 cylinders have less than normal compression. He said I may have to buy a new engine or get this fixed (which he said will cost almost the same as buying a new engine). PLEASE HELP!
Apparently, cylinders 1 and 4 are in a very bad shape and the head needs to be changed. But I was told the coils are OK. Along with changing the head, the mechanic said he’ll have to replace some other parts including cam and crankshaft sensors.
But he said it might need less work depending on what he sees after opening the cylinder head.
His quote was about $3k (apparently is takes 3 full days for this)!
Can someone please let me know if all this makes sense?
Thanks!
Can someone shed some light on the short block and long block ways of replacing an engine?
I am getting conflicting recommendations from two mechanics – one says short block is fine and the other insists on long block. The quote for long block is almost double that for short!
Also, would you recommend I get this done at the dealer’s?
Thanks!