Hi all
I'll get right into it. I bought a used 2008 Max SE, 140k miles for my 16yr old son. History on the car was a rental in California, made it to Michigan, 2 owners here. Last owner was local and had an accident with an animal (presume Deer). When I got it I did the usual maintenance, changed the belts, fixed an oil leak from behind the oil cooler, changed air filters ect. The kid comes home from a friends a few weeks ago and said it isn’t running right. My kid did say he went thru some water but it wasn’t "that deep" as it had been raining here for a few days. The next day I started it and it ran ruff missing really bad. Gave it some gas and it leveled out. Took it for a drive and at about 20-30mph the engine just cuts out. Sputters and lurches to the point it stalls. I thought it may be water in the gas so dumped a bottle of dry gas in, and barely made it home. My kid had to push me off to a side street when it stalled. So i had two codes P0300 multiple cylinder misfire, and p0463 fuel level high input (or whatever). I decided to change the plugs, none looked bad, and checked the coils all metered out to about 460 ohms. Once done I fired it back up and then unplugged the front bank of coils and noticed the engine change so figured the front coils were good, the back coils are under the plenum. At this point i cleaned the MAP sensor with the correct spray. Also found the CPS could be bad. So changed that. I did find something stuck on the end of the switch so thought yay found it. Fired it up and had had a high idle, was in the process of resetting the TPS and the battery died. Put it on the charger, let it go over night. The next day took it for a drive and the same problem, Idles fine, but under load the engine seems to choke out, almost like the traction control kicks in and the engine bogs hard almost to stall.
At this point i take it to the local dealer ship. They say it looks like the cat is plugged. I think to myself "Ok that kind of makes sense". I asked the dealer to do a back pressure test and they had never heard of that nor the tools, told him the muffler shops do it and the tool is like 40 bucks on amazon..... The dealer hits me for the 480ish to pull the manifold and inspect it. Result it’s not a plugged cat. Next day or two goes by they tell me it’s the O2 sensor in front of the cat bank 1 sensor 1. Back ground on that sensor, when I bought the car i noticed the connector was somewhat melted, it appears someone had to torch the exhaust bracket there and had done a real poor job welding something there. But as mentioned the car ran fine with that melted connector. Not saying it could have finally had water intrusion. I explained that to the dealer and agreed to change that. Now another 380 into this and the dealer called and said the engine runs much better but it’s not fixed, we have our shop supervisor on it now. Today I get a call and they explain the transmission needs replacing, some seal is blown, or valve body is bad or something internal is causing the car not to run right his words not mine. He noted the transmission fluid is correct type appears to be OEM, and that it’s over filled. I did notice it was over fill but it wasn’t running so thought it had to be running and warmed up. They want 4300 to replace the trans. This I cannot do! Especially after their 2 previous mis diagnosis Im hesitant anyway. Again the car idles fine, put it in drive and about 20-30 mph it cuts out hard spits sputters, back fires and near stalls. If it does stall restarting the engine seems to help but then does the same thing. Cat is not plugged, O2 sensor has been replaced, CPS has been replaced, plugs changed, coils appear ok, MAP sensor cleaned. I asked if it had good fuel pressure at idle and WOT, he was gonna ask the tech but didn’t answer my question. Car is no longer throwing codes; dealer did say there was an engine over speed or something I’ve never heard of. Sorry for being lengthy any one have any ideas?

 

Testing coilpacks is often inconclusive and they test ok even thought they are bad. Your symptoms sound like bad coilpacks, hence your codes. Possibly a bad MAF. I understand you cleaned the MAF, but cleaning the MAF rarely helps with these cars. If you get a new MAF, get a good used MAF from the junkyard; do not buy a new aftermarket MAF.

 

Thanks Wizard!
I understand the coils can breakdown when they get hot and hard to figure out which one is bad especially if i dont have a specific cylinder misfire code. I may try to swap back coils to front, then while running unplug one at a time to see if the engine gets grumpy. My gut says it wont change as they arnt really under load. Is there a better way? I would rather not buy six coils usually its one maybe two that fail. As far as the MAF sensor, they are a little pricy but can I ask why after market are not prefirred? Ive seen some posts about it with issues and suggestions on using the hitachi brand.

 

Update:
I picked up the car, looked at the bill and said I'll pay for parts and the diagnostic fee not the rest. Service rep said ok. So paid for 02 sensor, exhaust manifold gaskets (there were 3 that lead to the cat) and the 105 fee.
Fully expecting to need a tow home at some point in the 10mile drive I headed off gingerly. The engine ran fine! So the melted bank 1 sensor 1 O2 sensor connector may have finally shorted.
Next is the trans issue the steeler was talking about. Since ive never driven a CVT (outside of a snowmobile lol) it may be slipping but hardly noticeable. It shifts in and out of reverse fine. Doesn't jerk or shift hard. The only thing to note is rippms seem to wind up but not like over 3500 as it accelerates then settle at maybe 2500 as I reach 50-60mph. Not sure how exactly these behave. The last part is an over filled trans, so gonna try to siphen some out and see what the future holds for the trans.

 

Glad to hear you didn't get stuck with those outrageous bills considering they mis-diagnosed the issue. Also glad you got home ok, but I don't think you're out of the woods yet. Hopefully your Max runs ok and no more codes return. If the misfire code returns and doesn't give you a specific cylinder misfire code, you may want to consider getting one front used coilpack and 3 rear used coilpacks and go from there.

Our Maximas are very finicky when it comes MAF's, as many members have reported issues with aftermarket MAF's purchased from Autozone, Pepboys etc. Only use OEM. Hopefully that clarifies my previous suggestion.

Since you don't know the history of the car and the transmission, you may want to consider a simple drain and refill, and ensure it's at the proper level this time, rather than siphoning out the overfilled amount.