This is my buddies truck, he is retired, and doesn't have the time or money to take care of his ride, so I have taken it upon myself to take care of it for him.
got the truck with three codes, p0505 "sometimes idle rough, and stall, but unpredictable"and the 02 sensor codes, because he deleted the cat and disconnected both sensors. Supposedly the 360 has a tune on it, is what he tells me anyway. It has an MSD coil, and headers, with a TB spacer. He complained, because he said the thing used to have waaaay more power, and was stalling from time to time. To give you an idea of this fellas level, he let it run out of oil, lucky he didn't kill the engine till I got it to my place and rushed some lucas into it. I got it, and pulled the TB, cleaned the ever living dog crap out of it, and put a new IAC in it, put it all back together and now have this problem, I now have a new code, p0505, and p0171, with a bank lean code, this happened right after plugging one of the o2s in "the rear one" and hooking the other one up, but there is no bung, because he ran a custom dual exhaust with flowmasters. I checked the connections of the PCM, and new sensor, I even changed the Throttle position sensor with no distinguishable effect. I used sensor safe RTV to re-seal the TB and spacer, with the old gaskets, and sprayed carb fluid to check for vacuum leaks but none are present, idles fine right at first, but after driving I have to hold the gas to keep her running, runs super rich, and has a loss of both power and fuel economy "HORRIBLE" The front 02 is hoked up but not inserted into the exhaust. I want to hook it up to a solus, and run diagnostics on it but don't have access to one anymore. Haynes troubleshooting cross reference says the culprits are fuel or electrical, clogged air filter, fuel pump filter, or injectors, regulator, coil, wires, plugs "I installed new champion coppers gapped to 35" emissions control, or exhaust restriction "yeah right" p0505 is a hard code and comes right back. Has a nasty backfire upon decel. I am trying to clean the wires/terminals with baking soda and water, because I head that a bad ground can cause some or all of these issues, and the -neg terminal cable was pretty covered in corrosion, even after I trimmed it, and cleaned the terminal, and battery connector.

 

I just finished cleaning the terminals/wires, and started her up, no hard codes yet, but I want to go for a test drive first. Still a little backfire on decel. I'll try a reset.

 

Made a huge, significant difference, I drove it a few miles, with no codes. The monitors finally kicked in and threw these two. Started surging above idle and wanted to die at idle again. finally threw the p0171 and shortly after I arrived in my driveway it threw the 505 code. I'm stumped. Help please.

 

P0171 1/1 Fuel Sys Lean

So long as that front O2 sensor is not in the exhaust stream, this one isn't going to go away. Need to get a bung welded on for it.

P0505 Idle Air Ctrl Motor Circs

Check connections, see what you find, also check connections at the PCM. make sure you don't have any wires pinched between the IAC, and PCM. Is it still the original IAC?

 

nope, already swapped it, checked wires, but I'll check again. the connection looks good to the PCM, no corrosion, no broken/exposed wires, any instructions that can help me prove the wiring bad? if it was bad, wouldn't it be bad all the time? It hard coded before, then just stopped? IDK don't think it is a wiring problem, is there an intermittent issue that would cause this? crank PS? of Cam PS? going out soon? I'll let you know what I find, just as soon as I finish my sandwich.

thanks so far,

Nintendo

 

You might have just gotten a cheap IAC..... not like I have never gotten bad parts right out of the box.

You could disconnect the IAC, and the connector at the PCM, and ohm out the wires, should be hardly any resistance at all.... they may be rubbing somewhere, causing an intermittent problem as well...

 

I just had an OH DUH! moment that every so often happens to all of us. I left the front vacuum connector off of the TB, just plugged it back in and checked for DTC's none, but I'll need a good test drive to know for sure. DER DER DERR

 

It seems like it is worse than ever, I checked the PCV, and it is good. Now what?

 

Solus is a goot tool, but maybe you can find someone with a MTG or something. They can actually read the steps on IAC and compare whet PCM is sending and what its respnse is. And the port has to be clean. The IAC is a stepping motor and crud will interfere with it's steps.

And +1 on showing lean with O2 out, but in actuality it is probably running pig rich until it corrects what it thinks is "lean". No response, keeps dumping fuel.

How about the plenum? Can't find that as a vacuum leak with carb cleaner. That may be why cat was cut out before, and the cause of clogged cat not resolved.

 

I would unplug the front O2 sensor....... until you had a bung to stick it in.

Reset the PCM again. (clean the throttle body while the PCM is disconnected?)