97 stock Z28, driving home today my car started idling REAL rough. CEL came on shortly after, when i got home i ran the codes and P0172 and P0175 both banks running rich. the car will not start unless the pedal is floored and even then it takes a few seconds longer to start plus you can smell raw gas. fpr not leaking fuel, LT fuel trims are staying at 0 and the ST trims are going as high as -37 on both banks, also the temp sensor is reading fine. evap, egr, and rear o2 have all been removed and tuned out for a few years now. anyone have any clues as to where to look next?

 

test your engine coolant temp sensor. its the one on the front of the water pump. temp gage sensor is by the number one plug. it sounds like your ect sensor is failing or at least thats what i would look at first. 4th Gen LT1 F-body Tech Articles

 

i haven't physically tested the ect sensor but it is reading correctly on my scanner so i would have to assume that's not the issue.

 

ahh ok. wonder if theres a short at the 02s. check wires yet? i would consider looking at the injectors next to see whats going on there. test with noid light to see if they are being told to open all the time. if not then i would check to see if one or more is sticking. have to pull the rack for that.

 

man,,, both sides though almost sounds like a pcm problem. i guess it could be maf failing but i would think that would throw a code

 

that's the part that has me stumped, it's not something that happened over time one second at the light it was fine and the next second it was dumping fuel and idling so rough the whole car was shaking. also i would imagine the chances of both o2 sensors or multiple injectors failing and the exact same time to be near impossible, i will have to pick up another noid light set sometime this week as my current set has been missing the GM light for a number of years now...lol...i did a gear change a few months back and have been wanting to send the ecm back to the company that did my tune to get the speedo calibrated maybe ill spend the couple extra bucks and do the core exchange just to rule that out. also one more thing not that it should matter i do have a walbro 255 fuel pump in the car but its been in there for about 5 years now

 

i use the same pump and have 50k miles on it, still going strong. you already tested fuel pressure right? thats was the problem with mine. pressure was like 60 and fuel poured in

 

no i haven't i guess ive always been told that the fpr is either bad or its not, theres ni in between and is its bad fuel will come out of the vacuum port...lol...i guess i should go check the fuel pressure

 

check for any wires around the exhaust that may have gotten burnt. check ignition ground on the passenger side block, to the front of the starter.

 

so, Mr Computer is trying to lean out your mixture

check for an exhaust leak before the O2