**Car Won't Start...Gas Smell...HELP

Perhaps it is still a bad IAC.

Try this, crack the throttle half way and see if it starts. If it does, suspect a bad IAC.

The IAC is supposed to supply bypass air during starting. The vented IAC has a series of vents, springs, and diaphragms to allow outside air for starting. These do not take kindly to cleaning. Replace it.

I suspect that the idle will improve after IAC replacement. Autozone makes a lower cost replacement unit. I have had good results with them.

Yes, it could certainly be a bad IAC valve. If you can start the engine with a little bit of throttle and keep it running with a bit of throttle, but it dies or runs rough when you let off the gas, then it is most likely the IAC stuck. I've had to clean mine every winter for the last couple years because it is always sticking when cold. I should probably replace it through.

Next time this happens, try holding the gas pedal all the way to the floor and cranking it for maybe 5 to 10 seconds - this activates the 'clear flood condition' mode - and then try starting it again normally.

Another thing to try is when it's been sitting long enough that you know it will start, turn the ignition on and listen for the fuel pump to come on and then let it sit for a few minutes and see if you smell gas and if it's hard to start again. You might have a fuel injector stuck open and dumping fuel in the intake and flooding it when you shut the motor off and leaving you with no fuel pressure in the lines when you come back later leading to rough starting while the pressure builds back up.

I had the same thing happen to me ...you drive for about 30 min turn it off and then it wont start..try disconnecting the pcv hose from the thottle body and plug it up thats what i did works fine now..i hope you get it ...merry christmas: nice:

Are we talking about plugging the PCV system? Are you aware of what the long term effects to your motor will be? The crank case vapors must be removed somehow. If not, expect condensation amoung other problems.

For starting concerns running VERY RICH, the list of items include:

1. Spark/misfire problems (plugs, wires, coils).
2. MAF.
3. Excessively high fuel pressre. Bad regulator. FRPS. (test fuel pressure).
4. Leaky fuel injectors. Allowing FP to bleed down.
5. IAC (no starting air).

Since you are positive that the IAC is good, suggest a test of the fuel pressure. Use an ODB2 scanner to monitor FP at idle and higher loads. Should stay in a narrow range 38-41 PSI for a SHOC 4.6l.

Are there any mods we need to know about? After market fuel pressure regulators? Custom tune?

Note, for rich starting/running at idle with NO DTC's, the MAF is frequently to blame. Since yours has been cleaned already, replacement should be considered.

If you do not wish to replace the MAF, then data log the MAF, FP, LTFM, STFT, RPM, open/close loop, coolant temp, and post the results. Do this for serveral engine operation ranges (idle through say 2k RPM).

Another quick test is to disconnect the electrical connection to the MAF. If the starting/idle condition improves, suspect the MAF. This trick works because when a sensor fails completely (electrical connection disconnected), the PCM uses default values to replace the missing inputs. This will throw a DTC sooner or later but its OK because its for testing.