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If You Can Solve/Help W This, You'll be My Hero

Where to begin. I have a 2002 Nissan Sentra SE-R with the 2.5L Altima engine. It’s had recalls. A lot. Supposedly, these were all ‘fixed’ by dealers. In the past two months, however, I’ve had $1400+ worth of repairs directly related to the faulty parts (emissions/exhaust system).

Car threw an SES light in May or so. Was told by dealer it was main catalytic converter; out of federal warranty (I have 88k highway miles on it). They quoted $1200; I rolled my eyes, picked up a decent aftermarket catalytic converter online, and had a local mechanic install it for me.

A week or so later, the light goes on again. Turns out the dealer misdiagnosed the problem and it was the ‘pre-catalytic’ converter, not the main cat. (The local mechanic warned me about this but I figured the dealer wouldn’t just make that up…guess I was wrong.) I replace the pre-cat and header (because they’re attached in my vehicle, like one unit that goes to the main block), have it installed, all seems to be fine. I pass emissions, no SES light, car runs relatively smoothly.

Three weeks later I notice my car’s a little “shaky” at start up, but it still starts, doesn’t seem major. No lights. I use my scanner, no codes. Tuesday I try to go to work and the car won’t start. Try to jump it, won’t work. Have it towed to mechanic.

Mechanic tells me my Mass Air Flow Sensor was dirty & I needed new spark plugs etc. Car is fixed quickly; I pick it up Weds morning. Runs fine until Thurs night when the SES light comes back on again. I check the code and it says “multiple misfires”. ( Didn’t catch the number as I was just at this pt overwhelmed and wanted to go to sleep.)

I drive it this morning to the hospital to drop off food for a friend, and the car won’t start back up. It tries to turn over, but won’t start, similarly to Tues morning.

I didn’t see smoke coming out the back; it’s not overheating. Does anyone know what the expletive would cause this? Are these problems related? Could it just be bad spark plug wires, or has anyone else had this problem?? HELP!!!

Thank you : >

It could be that when he done the plugs, he may not have gotten the wires in the right places(firing order).
If that checks out, then the likely suspect would be o2 sensors, which have been known to throw the catalytic converter codes.

I don’t think there is much that can be done here as far as helping you with this car. Simply too many unknowns.

It’s possible that the converters could have been killed by other things; as is often the case.
A quick look shows you’re definitely right on the Recall situation. This model is apparently plagued with them and several involve things that could cause rough running, failing converters, etc.

I note there is a recall involving the crank sensor. Since this could cause random misfires and a no-start condition do you know if this particular Recall has been performed or not?

I think that your engine has “coil on plug” (no spark plug wires).
The mechanic had a chance to see how the engine has been running when he replaced the spark plugs. One can “read” a lot from spark plugs, as shown with these color pictures from Autolite:
If a misfire is indicated on a particular cylinder (P0301, P0302, P0303, P0304), you could swap the coil on plug to another cylinder and see if the misfire code follow. If it does follow, that indicates that that coil on plug is faulty.

Since the MAF sensor was worked on just before the problem I would recheck that area first.

If the mechanic had gotten the firing order wrong, the car would have run like crap from the get-go, not three weeks later. And even if the O2 sensors were bad, the car would still start and run.

Sounds like some basic diagnosis needs to be done—determine whether the car has both spark and fuel present when trying to start it. And knowing what malfunction codes are in the computer would be useful as well.