Deleted mufflers won't be significant enough to cause issues with back pressure especially since your still running stock cats. (Which adds a lot of backpressure) it could possibly be the short rams, as many posted before a bad/dirty maf causes a lot of weird issues

Sorry, the recent codes were different. P0420 and P0430 ("Catalyst System Efficiency Below Threshold" at Bank 1 and Bank 2). He said it's unlikely that both sensors went out, which makes sense.

Gotta be air/fuel mixture...?

Yes he is right it is unlikely both went out at the same time. If it is a issue with air fuel ratio it should be throwing a different code saying rich or lean. I suspect either electrical issues with those sensors or maybe (even though unlikely) both cats went out. I agree with trying to take it to a different mechanic maybe he will know.

Change bank one Oxygen sensor #2

reset car, by unplugging battery for 10 min, start, drive for 5-10 min, turn off, turn on look at CEL if no, then turn off, turn on, look again.


if codes come back, its probably the MAP sensor always keep receipt to get ur $ back.

Is this normal??? (pics)
 

Hey guys, I wanted to post an update and something new that I may or may not have discovered. So, I cleaned both MAF sensors and went out for a drive, no issues. After a few hours, drove it again, and it was so bad I almost didn't make it home. Just like before, the problem is still there and still intermittent.

I haven't looked at anything exhaust side yet but I'll check the MAP when I'm done checking intake side.

Recently it's been throwing a new code: random/multiple misfires! And I can definitely feel them. So, before attempting new MAFs, I thought I'd swap out the plugs. I took out the intake manifold and noticed what looks to be oil in 3 out of the 6 airways... is this normal???(for some reason can't get the images to show, but it works if you right-click the icon and open in new tab). (Also..where are the spark plugs located?? :icon17:)

https://c77i.imgup.net/2017-03-15118b.jpg

https://v48i.imgup.net/2017-03-151435.jpg

https://a03i.imgup.net/2017-03-10a425.png

https://q31i.imgup.net/2017-03-1016da.png

Wait, really?

You'll see 3 coils with looms coming from them on each valve cover. Take those off and you'll see them..

Thank you, I'm blind!! Also, I've driven older Saabs my whole life and they're very different haha.

Still wondering about that oil though. It's only coming from one side which makes me think something's up...

We've all been there, you just have a much nicer platform to learn on than I did back in the day lol

Someone posted a similar thread on this site. Even has pictures, IIRC. I don't remember what the conclusion was. If you can't find the thread using the site's search, try any of the web search engines and add "site:the370z.com" to your search string. Eg, "oil in manifold site:the370z.com".

The conclusion was that he replaced all his O2 sensors and cats to get it to work. That's way too expensive for me at the time, so I'm thinking of starting with the most likely cause.

Which one should I try first? To reiterate my original problem, I'm getting P0420/P0430 with random episodes of hesitation/no power, coupled with backfiring, rich-smelling exhaust, and now misfiring. I tried: cleaning the MAF sensors, cleaning the air filters, and changing the spark plugs already. Should I start with the upstream oxygen sensors or is it definitely the cats?? Any other ideas?

Oil in the manifold sounds really bad. Only 2 ways I can think of for that one. Over oiling the air filter or too much blow by in the block. Blow by would be the worst, happens from scratched piston walls or messed up rings. You could do a compression test while you have the spark plugs out. I'd guess it should be somewhere around 160. All pistons should be within 10psi range. Also look at your spark plugs. They should all look the same. A bad cat should not be intermittent. None of the really major issues should be intermittent. Good luck!

When I replaced the spark plugs, I noticed the old ones were not that worn and had all been worn evenly. I replaced them anyway.

You said a bad cat should not be intermittent and I agree, so could O2 sensors be intermittent? What about blown rings?

You mentioned that you haven't checked for exhaust leaks.

I had a P2A00 and my car was running sluggish and chugging gas, no misfires but just bad. I came on here to try and find a solution, everywhere I read it said that it was probably an intake leak, turned out that I had a crack on both catalytic converters. The crack was downstream the O2 sensor on the exhaust manifold and upstream the O2 sensor on the cat. I had aftermarket cats so I put the stock ones back on and it solved my problem.

I understand that you have stock cats and it is very difficult to damage them, but try and rule out an exhaust leak in that region.