Long story short. My G35c auto:

hardly revs past 2000-2500rpm

Runs 10.0 rich according to my wideband when applying a low percentage of throttle

Overall engine exhaust tone is lower-deeper-like its being held back, probably just the retard in timing.

Randomly when idling or driving in gear the engine will shudder slightly and i'll look over at the wideband and it will read 10.0. After several seconds it goes back to normal idle/cruising A/F.

RPM's are very sluggish, like timing is retarded to the max.

All 6 cyl fire.

No vacuum leaks.

Ive bypassed the utec and connected directly to the stock ecu, pulled the vortechs belt, tried a brand new MAF, used the consolt II to scan for codes, view engine data and reset autolearn twice.
I have my own obd2 scanner-no codes ever since all this. I did purposly disconnect the MAF and got a MIL just to see if it would come on. It, did and I cleared it.

I usually get rich on bank 1 & 2 MIL when I drive the car for a little while everyday i drive it from cold. There are no effects when I get the MIL. Easily enough I erase it with the scan tool. When I was on the freeway driving normally at full power the MIL came on. I didnt bother to erase it right away. My trip was about 50 minutes long and I felt a shudder on the freeway. From that moment on the cars been acting like its on max limp mode. I cleared the MIL which was onlyt the usual rich on bank 1&2. I managed to drive the car all the way back home the next day in this limp mode and never got a the usual MIL, running pig *** rich for the most part.

Do factory ecu's go bad? why isnt there a ****ing code? What do I do next.

Feels electronic

Im going to do a battery disconnect as a last ditch effort next.

550cc injectors,walbro 255, plenum spacer, exhaust utec and vortech.

Help, please.

~Dv8

 

it sounds like your vehicle went into whats called limp mode for some reason.like u stated....the ecu thinks something is wrong and wont let u rev past around 2500...tuners can fix this .i had this happen when i had my procharger and utec also....u deleting codes and resetting stuff is not helping and yes the ecu can go bad...good luck

 

Ecu's are not likely to just go bad for no good reason.

There's TONS of stupid reasons for our cars to go into limp mode. I was stranded on I-95 1/2 way through a 220mi trip with limp mode because my power steering pressure sensor went bad. I went crazy trying to find the problem... So don't overlook anything!

 

Ok so how do I find the problem, if theres no codes?

Do i seriously need to buy every sensor and do a process of elimination?

Thanks

 

you're running larger injectors and your ecu is not made for them without the utec that might be the reason you're running so rich don't flame me this is my first post just wanted to help if i could

 

Im sorry but look at his sig and he is running a utec........nice try for your 1st post.I hate to say this but i think you need to call your tuner.

 

Ive bypassed the utec and connected directly to the stock ecu, pulled the vortechs belt, tried a brand new MAF, used the consolt II to scan for codes, view engine data and reset autolearn twice.

I don't know how to qoute previous articles so I just copy and pasted but he said he disconnected the utec I don't know if he was having issues before he did this but without utec to compensate for the changes in injector sizes its gonna run rich

 

Bro's

If you re-read my initial post, i specifiy that I have bypassed the utec(since I was having the issue) without changing the problem. Furthermore the Utec is a piggyback and doesnt control anything until I start to boost under speed density mode. Eitherway; connected to the utec or not this problem persists.

Now I know the ECU is in failsafe mode, but I dont know why, because theres no MIL/CEL. What I can tell you all is that from a cold start after reseting the ECU via a 12hr batter disconnect, the fail safe mode is immediate which is leading me into looking at the crank and cam sensors since I have already ruled out the MAF. The O2's should be ruled out too since they only take effect after the cars at temp.
I'm probably the best tuner to call before dropping the car off at the dealership or infiniti mechanic. All I lack are the tools to test the sensors. A something scope is what I need.
Im going to look into TSB's or recalls at this point.

Thanks, anyone else?

~Dv8

 

Cam sensors could be the issue. Crank sensor is also a possibility - all are right around $75 each and super easy to change Not to scare you, but you might also want to check your crank pulley and make sure that its properly torqued and that there are no issues with the keyway.

what are you using to scan codes? if just a normal scan tool, you might want to pick upa cipher, so you can actually log the car while you drive and isolate what else is going on when the issue occurs

 

Thanks, good advice.
I checked the cam and crank sensors resistance yesterday and they fell within spec. I know that the possibility is that they can still be bad. I'm waiting until tomorrow to call Infiniti consumer affairs. I need to know if my G35 received the sensor recall of 03's service before I go spending anymore money. Interesting is that the picture of the sensors in the service manual shows the connectors with an angle plug where as my installed sensors are straight plug. Maybe they’ve already been changed out to the newer spec?

Crank pulley? I’ve never touched it but I’ll check it. Any reasons? Actron 9175 scan tool.

 

A few years ago, I had a 3000GT that was acting a similar manner... was bogging down, running super rich (it was actually spraying unspent fuel out the exhaust). I checked the voltage on my injectors while firing, and 4 of them were staying on full time, instead of pulsing. Ended up being a problem with the ECU.

May not help ya much, but for what its worth.

Also, are you 100% sure its in limp mode (how does one tell?) -- don't go down a wrong path based on even a seemingly safe assumption. There have been times when I replaced parts, and had the same problem, and it turns out the new part itself was ALSO bad.

 

knock sensors can pull timing if it's seeing "noise".any clinks or rattles that could be fooling it?if the knock sensor see's something it gonna pull timing and never trip a code.....it thinks that it's doing its job.(been there,very frustrating chasing ghosts)

 

UPDATE!

My tuner kept at it for a day and finally found the problem.

The catalyst became loose and was plugging up the drivers side cat-exhaust flow.

The material isn't melted or broken, but whatever was holding it in place no longer is, because its just rattling around in there.
Personally I thought there would be a lot more catalyst in there than just a round 2 inch wide piece.

Thanks, you 350z guys have definitely helped me out the most online.

~Dv8

 

relatively simple....good stuff all things considered

 

Cool glad you found the problem.....luckily for me mine just just burnt up and there was hardly anything left.

 

Brand New Berks installed, no more issues. The other stock cat was showing some signs of going as well. Not a whole lot of catalyst in stock cats, I was surprised.

No CEL/MIL on the Berks. Seems to hit same boost psi as before maybe a little less. I'll take some logs later. Im getting the car back on the dyno soon to fine tune the new HFC's.

Its little raspier sounding with my HKS knock off dual path exhaust. Overall pretty much the same sound.

Thanks.

Thanks, Kyle(Houston) for the Berks.

~Dv8

 

Nice detective work especially without a code to help out. A blocked exhaust is not something that would have come to mind. Kudos go to your tuner.

 

Wow...catalyst problems....same thing happened to me....my tuner was wondering why my car was pinging during boost, and we found out the stock cats were burned out/melted and all this crap came out of the cats when I took it off my car....switched to crawfords and no problems (except for a little unwanted rasp)...

I guess I'm kinda hijacking the thread (congrats on fixing the problem OP), but anyone else experience bad stock cats? I mean I only had 50k miles when my stocks cats went bad...what's up with the stock nissan cats?!

 

I'm almost at 50k myself. Only 2k of its been SC'ed and one of the cats fell apart inside.
~Dv8

 

That's not the first time I've seen that with stock cats.
The same thing happened to an FX driver at 20K miles.