Very rich A/F mixture, cannot figure out the cause

[LSzajmi]

Hi guys!

I have a 2004 Civic Type-R (EP3) and after cleaning my IACV valve, the car started to run crazy rich, spitting fuel out the exhaust, and starting to misfire when I put load on it.

- Injectors are not leaking (all checked, also got new o-rings)
- New spark plugs (all of them give a spark)
- New O2 sensor (was working fine before)
- New MAP sensor
- No visible vacuum leaks
- No CEL (except for P0300 random misfires, if I drive the car)

Every time I start the car 2-3 seconds later fuel is coming out the exhaust, so it happens in open-loop as well.
I also tried removing all connectors on the TB one by one, none of them made it better.

I have no further ideas on what could the problem be, so I am waiting for your advice.

Thank you for the replies!

[M_A_S]

Was it running fine before you touched the IACV?

[LSzajmi]

Yep, everything was fine with it.

[M_A_S]

Then either you've screwed it while cleaning it or you haven't put it back properly.

Why did you clean it?

[LSzajmi]

My idle was too high at times, that's why I cleaned it.

If I screwed anything up with the IACV, could it cause such a rich mixture?

[GreenV8S]

Check the vacuum reference line to the fuel pressure regulator is intact and connected at both ends. Also check you haven't dislodged the PCV system.

[LSzajmi]

The PCV seems to be fine, the fuel pressure regulator in my car is one assembly with the fuel pump in the back, I'm gonna check for any anomalies there too.

[Mignon]

I find it extremely unlikely that unburned fuel would be coming out of the exhaust in actual droplets if that's what you mean and I suspect you're seeing water. The IACV wouldn't cause that anyway.

[LSzajmi]

I don't think either that the IACV could cause such a rich mixture. More likely I screwed something up on the TB while cleaning it, but I cannot figure out what.

It is definitely fuel coming out the exhaust, not in droplets, but smoke. It smells like unburnt gas, and there is no oil or coolant coming out with it.

[E-bmw]

Don't mean to sound argumentative but I seriously doubt it.

If you has un-burnt fuel being passed through the engine, the next exhaust pulse would ignite it.

[Mignon]

You originally said "spitting fuel". The word spitting implicitly means something do with a liquid. i.e. droplets of fuel. Now you say it's just smoke. Maybe this is a semantic problem with your usage of the English language but we can move past that. So it's smoke. Fine. What colour is the smoke?

Anyway, regardless, it's unlikely that anyone here can tell you what you did wrong. You need to check for wires you unplugged and didn't put back. You also now say you cleaned the TB which you didn't mention before. If this still opens properly and closes fully I can't imagine what else could be wrong with it. Maybe you got water or something else in the throttle potentiometer which could cause all sorts of problems. You should be able to check the ouput of the TP as it opens with a voltmeter.

[Boosted LS1]

Unburnt fuel creates black smoke and stinks. If it's water it'll be white and your hand will get wet if you hold it over the exhaust tip. It won't stink of fuel.

[Ive]

if you accidentally swap the TPS and the MAP sensor plug on the throttle body, you'll destroy the MAP sensor. I guess you can guess how I know.
They use the same plug and the wires are long enough to swap them.
It will read fixed high pressure leading to a very rich fueling with the throttle closed.
If you have a Kpro/Doctronic ECU, check the MAP reading in the ECU with the engine stopped. It should show some 950 to 1050mbar depending on air pressure.
An OBDII reader should also allow you to read out that value.

[Chromed]

Once I had a very similar problem, in my case it turned out to be the wiring to the MAF. Good luck.