Misfires after Oil Change

[Hollowbelly15]

I have a 99 Maxima SE, 160K miles on it and I just switched it to synthetic oil from conventional. Before the change, there were random intermittent misfires that set off the check engine light every other month or so. After the oil change, there were bunches of misfires, the engine hesitated constantly and there was almost no acceleration.

Could the change have caused the problems? I suspected fouled plugs after I cleaned my K&N filter and found that the shop had left it smothered in oil last time they did it.

Any help/ideas?

[Markc]

IMO, there's no way switching to synthetic could cause mis-fires. When were the plugs last replaced?I'd be looking @ the MAF, (because of the excess oil on filter, not the symptoms per say).If it were me, I'd lose the K&N and go to a dry type filter.Symptoms kinda lead to plugs, coils and injectors.Get the codes pulled and take it from there.

[loystock]

Mark is right. Your entire air intake is messed up because of that K&N filter. You have to thoroughly clean MAF sensor and Throttle Body, and probably the IACV and EGR valve and tubing too. Have the car scanned for additional info.

[Hollowbelly15]

Ok, this all makes sense. I'm going to replace the plugs and clean all that up then get it scanned to see if anything else is wrong. My biggest question is why did the symptoms not show up until after this oil change?? It's so weird.

[NutriaforBreakfast]

You will have the coils off anyway. I would be a good timeto check them. Look for cracked coils. If there is any motoroil on them the you may need to put in new seals in yourvalve covers. Although not foolproof, you can check theresistance with a multimeter and see if they are gettingthe correct voltage to them

[Hollowbelly15]

Plugs changed, MAF and Throttle Body cleaned, and the car runs fine again. I still don't know why it only happened after the oil change, but that's fine.

thanks for all the help here.

[Markc]

Glad to hear that it worked out for you. Hope you got rid of that K&N filter.

[NutriaforBreakfast]

Carbon fouled up my IACV making the car run bad onceYou probably had some in your throttle body

[Hollowbelly15]

So, yeah, the whole thing came back.

It's always really bad when the car is still cold, but it tends to get better once it warms up. It never goes away, though.

When idling at a stop light, the car hesitates and hiccups. I thought everything was cleaned out, but something is still wrong. Oddly enough, my check engine light never comes on.

I feel like it's probably a coil - how do I measure the resistance or check if they are in shape?

[loystock]

Problem with ignition will usually throw a fault code and turn on the CEL. So it could be the IACV as suggested by 'nutria' or you may have an internal failure in the MAF sensor (cold solder or cracked board). BTW, did you clean the MAF connector too? I always apply dielectric grease on connectors to prevent corrosion.