Hey guys, so I chased down all my misfire woes and changed out the plugs, wires, and coil packs. Also changed out both pre-cat O2 sensors. The scanner is showing a p0150 and p0171 now. There's also a rough idle only in drive. The odd part is that the SES light isn't on, but the scanner is picking up the codes. I unhooked the IACV and ran it without it hooked up and it cleared up the rough idle and codes. Now it's just the throwing the IACV codes p1551 & p1514.

What does the IACV do exactly? And can I run it without the IACV? My state has no emissions test if its simply a smog thing.

Thanks

 

Many codes are "multiple offenders" in that they must happen on two or sometime more drive cycles, before the engine light comes on. You are seeing a pending code.

IACV is a computer controlled vacuum leak that makes idle smooth. You need it connected. The IACV can be cleaned with carb cleaner.

 

Thanks Buzz, I cleaned it out and it didn't fix the issue. Ordered the IACV, so we'll see if that clears the issue up. All this happened after power washing the motor; since the IACV is right on top, I'm assuming it took the brunt of the wash.

 

I cleaned the IACV, didn't change anything. Bought one and changed it out. That fixed it for like an hour and now the same codes are back.

Anyone have an idea as to why the codes don't show up when the IACV is unplugged?

 

You have a failed 02 which is causing the 171 which is the reason for your rough idle. Deal with the and leave your IAC alone before you break it.

 

I changed both pre-cat O2 sensors in the past 2 weeks.

And just out of curiosity, how would I end up breaking the IACV by unplugging the connection?

Thanks

 

Anyone know why the codes disappear when the IACV is unplugged? I'm lost at this point.

 

If you had a better understanding of the idle control solenoid you might get it. With it unplugged the engine has no way of maintaing an idle because the IAC is the only way the engine gets air when your foot is off the gas.
As for the codes, if you have replaced the 2 front 02's, have you verifiey that the 02's are working per a scanner and did you clean all the oil out of the connection?

 

Thanks Mike, that's why I was asking what role the IAC played since it ran fine with it unplugged. I was trying to expand my knowledge on that subject.

I checked the O2 sensors with the scanner and bank 2, sensor 1 was reading 0. I swapped the two front sensors to see if the 0 reading followed. It followed, but the p0150 stayed along with a new p0154 code.

I believe I got a faulty O2 sensor from the auto parts store, so I'm swapping it today. I'll let ya'll know if that fixes the issue.

Also, I've cleaned the connections a few times to ensure there is nothing blocking signal.

Thanks

 

MtnRunnin,
Have you opened up the engine wire harness above engine on firewall to see if it got wet during pressure wash? This should be easy enough to do: un-clip it and un-tape it. Look carefully for bare or corroded wires. Also, you might want to check to see if water got in the harness through firewall, and followed to ECU connection up under glove box, causing corrosion ("fretting" in technician parlance.) Good luck!