Poor idle when cold

[rp23g7]

so, i posted about my 99 Explorer 4.0 SOHC idleing poor when cold, but running ok when it warmed up a week or so ago.

I tested it with a scanner and got a P0171 and P0174 code.

Today i replaced the upper intake manifold gaskets, they were pretty old and hard, replaced and put the engine back together.

I did not reset the computer and didnt scan it yet, as i had a borrowed scanner, but i started it cold and there was no change in the way it idled before or after the gasket replacement. Once again when warm it idled fine.

Last week, i had reset the computer and was checking the MAF sensor. I cleaned it, maybe with too much electrical cleaner.

I started it cold, and then unplugged the MAF, it idled better cold, but (it was cold outside) started pumping out clouds of condensation(too much fuel)?

I plugged it back in and the clouds of condensation disapated, by then it was warm and i took it out for a drive.

At about 30 or 40 mph, or when under a load, it would start smoking grey smoke(possible rich mixture)?

It did this for the next few startups. After the 4th start or so, after a few errands it stopped smoking. The next day, it did not do this any longer, i assume the computer had started compensating for it. The engine light didnt turn back on ill tuesday.

Any ideas for my next attempt? MAF sensor replacement?

 

[fixxxer]

Check your lower intake manifold gaskets and the lower manifold bolts, you could also have a vacuum leak somewhere else, maybe caused by a unplugged or leaking vacuum hose, also check your engine coolant temp sensor and IAC valve

 

[rp23g7]

Thanks for the reply fixxxer,

I had replaced my IAC about a yr ago, no change in the issue.

Engine Coolant Temp Sensor? Would that make it idle bad? Temp gauge has aways seemed to work ok.

 

[fixxxer]

There are two sensors for the coolant temp. One supplies signal to the gauge and the other supplies signal to the engine's computer. The computer uses that signal along with the IAT (Intake air Temp) and the MAF (Mass Air Flow) to control the opening and closing of the IAC valve and and the injector pulse duration, so yes, any of those could adversely effect your idle, engine performance and fuel mileage.

 

[rp23g7]

hmmm, i will have to check that out, thanks