300Z5

i baught a 2000 ford explorer and its having some type of problem when you first start the car in the morning when its cold it sputters and wants to die but then when you throttle on it a little it revs up just fine i was wondering what that problem could be and when it warms up it runs perfectly fine.
its a 4.0 v6 sohc

dreamer1uk

Hi,

Did you check fuel pressure? Is it a returnless or return style fuel system? You could also do a injector leak down test also...

MU71L4710N

easiest things first try just cleaning your MAF, iac, and throttle body.

hiboostwoody

Bad intake gaskets. VERY common on the 4.0 and what you described is the classic symptoms. I see this almost weekly at work. It also just happened to both my sister and mom's Explorers. Their's are also both 2000's.

300Z5

its wierd because it only dose it when its cold like if i start it up and it warms up its perfect, but then if i shut it off for for like 6 hours and try start it back up it dose it

hiboostwoody

That's because when the engine is warm the computer is in closed loop. Also, the gaskets tend to swell and stop leaking when the engine gets warm. Trust me, it's the gaskets.

dreamer1uk

Do you have a CEL? Usually the Exploders are prone to the P0171 and P0174 which is a lower intake manifold gasket leak.

hiboostwoody

Not exactly. P0171 and P0174 are bank 1 and bank 2 oxygen sensor codes. While a leaking intake gasket CAN cause these codes, there are a lot of other things that also can cause them. HOWEVER, the symptoms OP described are classic leaking intake manifold gasket symptoms.

hiboostwoody

I got this from Identifix:

Ford program 00M12 was released to address leakage of the lower intake manifold to head
gasket seals, as well as the gaskets between the upper and lower intake manifold which will
typically leak during the cold engine warm-up phase of the engine. After the PCM enters closed
loop operation, the PCM can adjust to lean O2 sensor readings and thereby potentially
overcome the vacuum leak with its adaptive fuel strategy. When the engine reaches a raised
temperature, the gaskets have a tendency to expand from the heat and seal the leak, resulting
in a reseal type condition that will cause the PCM’s adaptive fuel control to drop back to singledigit
values. In severe cases of this problem, the MIL will illuminate and the PCM will set a code
P0171 and P0174 in Keep Alive Memory (KAM).

dreamer1uk

Yup, you was 100% right to question my post. I was actually discussing these P0171 and P0174 codes with my current college teacher this past Tuesday who still works for Ford. He said that 'usually' those codes on an Explorer mean a intake gasket problem.

However, anytime i work on a vehicle with bank 1 and bank 2 lean codes, i always look at the STFT and LTFT values to see what exactly is going on. Some faulty MAF's can cause a P0171 and a P0174 if the STFT and LTFT are opposite of each other.

I wouldnt exactly point P0171 and a P0174 directly to been O2 sensor codes due to vacuum leaks, cracked exhaust manifolds and so forth

I fixed an 01 Kia Optima yesterday with a P0171. It ended up been a huge hole in a vacuum hose after the MAF on the upper intake The shop she took the car to told her she needed a MAF and whats sad is, that wasnt even a problem, nor a code on the CEL Plus it tested fine

And i LOVE your signature hiboostwoody! LOL!