Randomly running rich

[Redsvtcobra55]

So i have a 99 cobra (terminator engine) built with diamond pistons, slightly higher compression. I recently started having an issue where it will be full rich 10.0 on the wideband. Cruise around and itll go back to 14.2-14.5 while cruising around, then ill apply a little throttle to get over a hill and it’ll go full rich again. Sometimes while under deceleration itll go full rich, sound weird, act weird, etc. im at a loss here. Tried cleaning the maf, replaced both o2 sensors today and still have the same issue. It happened out of no where. I replaced the exhaust gaskets as well. Could a bad injector be causing this? At WOT everything is fine so i have no idea where to even go now. Ive gotten so annoyed with it im just letting it sit in the garage

 

[BlackStang00]

Have you datalogged while trying to recreate the issue? I don’t see it being an injector if it’s only intermittent.


Sent from my iPhone using Tapatalk

 

[Redsvtcobra55]

My tuner is so old now it doesn’t have real time logging. I suppose i should drop the cash on a new one. Just trying to figure it out troubleshooting it

 

[BlackStang00]

As a stopgap measure you could get an elm327 dongle and use it with Forscan on your phone, if you can. It’s a nice tool to have. Anyway I’d suggest that than chasing symptoms. Others may have had the exact problem and can tell you exactly what it is though. In the meantime, try the basics like compression and checking the plugs.


Sent from my iPhone using Tapatalk

 

[railroad]

I really do not have a clue, but might consider a plug check and see if they are consistent looking. Anything out of normal on a single cylinder might indicate a bad injector. I guess it could stick open.
Hope you find something simple.

 

[01yellercobra]

You need to datalog and watch the fuel trims. The wideband might be going out. So comparing what the ECU is seeing to what the wideband is showing would be the first thing I'd do.