Rough idle sounding like it had a stage one cam installed

[k1500 97]

I'm at a loss as of right now, finally got my timing correct, but now at idle it acts like it's cammed and I get a cylinder 4 misfire but it doesn't always show, it goes from Radom misfire to #7misfire to #4 misfire, and I have a lean bank 1 code. The truck runs and smells almost like raw fuel idk how I could be getting a lean code.

I have true duals ****** but the side that's showing lean sucks back like if I hold my hand over it, the other side is fine, sorry if my words aren't the greatest.

 

[fancyTBI]

You’re going to have to do some basic diagnostics first and address your codes.

 

[k1500 97]

Ok so after a lot of observation, I'm only experiencing problems after a when I fill up, once I get to half a tank everything is fine, besides my exhaust leak. To me that sounds like evap issues or fuel pump/regulator/injectors. This is not a question it's what I'm experiencing from my observation.

 

[Schurkey]

I'm at a loss as of right now, finally got my timing correct, but now at idle it acts like it's cammed and I get a cylinder 4 misfire but it doesn't always show, it goes from Radom misfire to #7misfire to #4 misfire, and I have a lean bank 1 code. The truck runs and smells almost like raw fuel idk how I could be getting a lean code.

I have true duals ****** but the side that's showing lean sucks back like if I hold my hand over it, the other side is fine, sorry if my words aren't the greatest.

WHAT VEHICLE??? WHAT ENGINE??

Misfire causes rough idle. Misfire results in a false-lean O2 sensor reading. the engine can be pig-rich, and the O2 sensor can still show excess oxygen in the exhaust stream. Misfire can also murder the catalyst, which results in "rich" smelling exhaust. 'Course, if you don't have a catalyst, you can EXPECT the exhaust to smell bad...just like 1974 again.

If the exhaust "sucks back" I'd be conducting a cylinder leakdown test looking for leaky exhaust valves.

Verify all the usual "tune-up" items--distributor cap, rotor, plug wires, spark plugs, PCV valve, EGR system, electronic spark advance.

Check fuel pressure at prime and under load.

Connect a scan tool, verify EVERY sensor and computer output. Look at the fuel trims and the misfire counts.

I'm only experiencing problems after a when I fill up, once I get to half a tank everything is fine,

Probably want to check-out the fuel tank venting, charcoal canister, purge valve, etc. No idea how that could be on the pump or pressure side of the fuel system, though. If anything, it'd be reversed--OK when full, problems as the fuel level drops.

 

[k1500 97]

WHAT VEHICLE??? WHAT ENGINE??

Misfire causes rough idle. Misfire results in a false-lean O2 sensor reading. the engine can be pig-rich, and the O2 sensor can still show excess oxygen in the exhaust stream. Misfire can also murder the catalyst, which results in "rich" smelling exhaust. 'Course, if you don't have a catalyst, you can EXPECT the exhaust to smell bad...just like 1974 again.

If the exhaust "sucks back" I'd be conducting a cylinder leakdown test looking for leaky exhaust valves.

Verify all the usual "tune-up" items--distributor cap, rotor, plug wires, spark plugs, PCV valve, EGR system, electronic spark advance.

Check fuel pressure at prime and under load.

Connect a scan tool, verify EVERY sensor and computer output. Look at the fuel trims and the misfire counts.


Probably want to check-out the fuel tank venting, charcoal canister, purge valve, etc. No idea how that could be on the pump or pressure side of the fuel system, though. If anything, it'd be reversed--OK when full, problems as the fuel level drops.

Sorry I forgot to mention it, it's a 97 with the 5.7 vortec, the only time I'm experiencing it is above half a tank give or take, I did replace the filler neck and vent to the tank, I had the problem before hand but it wasn't as bad, but ever sense I did that it's been way worse.

 

[k1500 97]

Probably want to check-out the fuel tank venting, charcoal canister, purge valve, etc. No idea how that could be on the pump or pressure side of the fuel system, though. If anything, it'd be reversed--OK when full, problems as the fuel level drops.

Yeah I'm confused my self, none of my evap sensors are throwing codes. unless I unplug them which is obviously why.

 

[k1500 97]

I got er fixed boys, the bank 1 and 2 o2 sensors where shot (both sensor 1)

 

[Schurkey]

I've seen fresh O2 sensors make wonderful improvements in driveability.

I don't see how new O2 sensors fix exhaust "suck back", or cause issues only when there's a certain amount of fuel in the tank.