i recently installed an exhaust on my car. and i did not tighten up the exhaust enougn where it meets each cat. so today i got back under the car to tighten it up better all said and done the exhaust is much quiter i go to drive the car and i hit 2500 rpms the car falls on its face and basically has a 2500 redline right now... i assume some sorta limp mode kicked in for w/e reason so i unhook the battery let it sit and try again this time it goes up to 5500 and does the same thing. after doing that it goes back to the origonal 2500 rpm limp mode... does anyone know why this would be happening simply from tightening my exhaust and also how i make it stop happening... no cels or anything just this symptoms

 

You disconnected or broke the O2 sensor(s).

 

wouldnt i have a cel?

 

I would have thought that to be the case. If it's totally disconnected, then limp mode might be the default state since it doesn't have any signal to decided to throw the CEL from.

I've seen people install a CAI or popcharger and forget to reconnect the MAF. When they try to start it, the car runs for a short time and dies - no CEL or code.

 

hmmm its night now i will have to climb back under tommorrow and check. idk how ide of disconnected those and no noticed i did it. i mean they are close to the flange but not right on top of it. thank you for the help Dave.

 

A CEL will only come on after two OBD-II drive cycles. It is totally possible that you have a pending code that hasn't turned on your CEL light yet (which is probably the case).

BTW, 'no signal' from the O2 sensors is still a 'signal' to the PCM. It will still set a code eventually. Probably O2 low input, P01xx, don't remember off the top of my head.

 

so chances are something is seriously wrong and its not just correcting itself for the change in air flow?

 

Yes, something is wrong. If it were just correcting for airflow changes, the LTFT (Long Term Fuel Trim) would compensate, and you would never know it.

"Limp Home" mode, (or FMEM (Failure Mode Effects Management) as we at Ford call it), is a failure strategy designed to enable to owner to drive the vehicle to the dealer for service, without having to tow it. I would highly suggest taking it to the dealer as soon as you have a chance.

 

just drove it again and it drives absolutley fine.so i parked it and gave it another 2 hours drove it again. it drives smoother than it did before i fixed the exhaust...i had a slight hesitation around 35-4500 rpms its gone now. i brought it to redline and stuff so should i still make the 1 hours trip to the nearest nissan dealer or am i ok?

 

If it drives fine now, you should be ok.

 

Guilty...yay limp mode.

 

i didnt disconect my mass air flow sensor? i went to see if im throwing any codes and just not showing a cel. so heres what i got... i have 2 pending codes p1271 and p1281 anyone got any guesses? i cleared them it helped for a bit then did it again? i see the p1271 is a air fuel sensor code but im not sure what p1281 is...my car doesnt need to be tuned or something just from a cai spacer and true dual does it?

 

anyone?

 

P1281 is probably the air fuel sensor on the other bank.

Do you have test pipes?
Is there any way you could have damaged your O2 sensors installing your exhaust?
Is there any history that might be relevant?

 

no test pipes just cai and spacer. only history is i had a exhaust i didnt tighten it enough... it leaked i put new gaskets on and some high temp gasket sealent... and tightened the heck outa it now it doesnt leak but my car wants to die lol. it only does it sometimes and when it doesnt limp it has a slight hesitation at 5500 rpms which is where its been going into limp mode at...

 

so basically the answere is i messed upmy o2 sensor...or no one knows lol

 

thats very weird tho the same exact thing happened to me wen i installed fujita intakes.....fujita sent me a new passenger side tube and it worked fine right after? maybe the exhaust was not constructed successfully or it is a defect?...just a thought?

 

your saying its cutting fuel at 5500 or you hit 5500 and thats when your throwing your code? cause u cant be in limp mode and hitting 5500. cause personally every time ive been in limp mode ive had a cel? is that right? also did u put liquid high temp gasket sealent on? any chance u got any on ur sensor? just a few thoughts maybe someone else may kno better.