I'm trying to fix up my 5 speed camaro good enough for the guy that's buying it to drive it home with no problems. It runs very rich and you can smell the gas. The only thing I can think of is the adjustable fuel pressure regulator being set too high maybe. What is the fuel pressure supposed to be set at for stock 305? Any suggestions on what this might be? I've fixed all the vacuum leaks under plenum and I've replaced cap, rodor, plugs, wires, different throttle bodies, new fuel filter..
Input would be much appreciated

 

bad o2 sensors can make it run rich

 

It cuts in and out though making it run really rough and then it will snap out of it for a second then start running rough.. Are you sure it's nothing with the fuel injection? Vacuum leak? Exhaust leak?

 

not sure, but they are cheap and easy to replace. good starting point and you already replaced alot of other stuff. had a 92 lumina z34 that ran real rich, blowing black smoke and stained the rear bumper. it did idle rough also. the friend i got it from replaced all kinds of stuff too. i put in the sensor and it ran fine. so simple

 

42- 43.5 lbs for the fuel pressure. And I also would change the O2 sensor.

 

thanks for the input its the first thing im going to check!

 

thanks i will also check that. will lowering fuel pressure lean it out or does fuel pressure have that effect? Also is this 42-43.5 WOT? and also im kind of unfimiliar with the term "closed" and "open" loop ? whats it referring to with fuel pressure?

 

[QUOTE=iroc-z_23;4762899]thanks i will also check that. will lowering fuel pressure lean it out or does fuel pressure have that effect? Also is this 42-43.5 WOT? and also im kind of unfimiliar with the term "closed" and "open" loop ? whats it referring to with fuel pressure? Closed loop, is when the engine is first started (cold) the ecm doesn't recognize the O2 sensor to regulate fuel, it just works on a preprogram. Open loop is after the engine warms, the ecm opens up the O2 and other sensors to regulate the fuel. Checking the fuel pressure should be done at idle with the vacuum line disconnected from the regulator and the vacuum line plugged.https://www.thirdgen.org/open-loop-closed-loop

 

[QUOTE=red rock;4762938]Thanks a bunch I think I'm on the right track here!

 

[QUOTE=red rock;4762938]It is open loop at start-up and goes to closed loop when o2 sensor gets heated up.

Having the fuel pressure too high could definitely cause it to be running rich.

 

Yea i guess i had open& closed backwards, sorry for the wrong info., it was late, she had her clothes off and i spilled by beer?

 

turned out NOT to be o2 sensor, but a hair line crack in the o-ring of the fuel pressure regulator. i took upper plenum off and dumped gas out.

let that be a note that if your running really rich, always check your afpr vacuume first.

 

Good catch, how did you find that it was a bad o-ring. Did you completely take the FPR apart and notice a cracked o-ring?

 

Well when I disconnected the vacuum line to the afpr it was spewing gas into my plenum so that right there told me theres something wrong right there and once I got to taking the plenum off to get to the afpr and took it off I couldn't even see the tear just looking at it, had to stretch the o-ring to see it. I can't believe that was the problem after spending 100s in other things that were fine, but luckily it was an easy fix and the guy was pretty happy with the car

 

But it has a new o2 sensor anyways lol

 

Never mind, I should learn.....read the WHOLE thread.

 

Never would of thought a temp sensor would make it do that, but yes found the problem thanks though

 

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