Bad O2 sensor causes stalling at idle?

[trueknight]

Bad O2 sensor causes stalling at warm/hot start idle?

I have a 1998 bone stock 4D, RWD Explorer XL 4.0 (EFI? It's not the SOHC one). It doesn't have any problems starting cold but rather it has problems starting if stopped/off for less than 45 minutes. It would crank and just when the RPM idles out, it would stall. I don't know if it is related to the o2 sensor as a couple of months ago, the engine light was on and it threw a o2 sensor code (forgot if it was p0133 or p0135). The engine light is currently not on (never came back after reset). After several tries or after waiting 45 minutes, it would eventually start normally again. However, I realize that this puts a strain on the battery. It never stalls while driving or during a stop light. Any help is greatly appreciated. Thanks.

 

[jremington59]

You might want to check the idle air control valve.

 

[davem]

I replaced a fuel pulse dampener on my 2001 V6 that had similar symptoms.

The thing was flooding, and the wait time allowed the fuel to dissipate enough that it would then start.

 

[koda2000]

not saying that a bad O2 sensor is your problem (i'd clean/check the iac first) but yes, a bad O2 sensor can cause a stalling problem and may, or may not, set the CEL.

 

[trueknight]

Replaced iac valve tonight with a duralast from autozone. Cost $42. Problem still there.

 

[trueknight]

Does anyone know exactly how many o2 sensors are in this particular model? I'm in Southern California if that matters. I searched online and it seemed to vary between 3 or 4.

 

[metal4life]

I beleive all the 4.0s have a total of 4 O2 sensors, I had to replace one of mine recently, and as it turns out the hardest part of the whole job was unplugging the wiring harness from the sensor. But it was $50 and it fixed that particular DTC, however other problems surfaced which the dealer traced to a single spark plug, replaced it for the price of an hour's diagnostics all at once, but they did tell me the fuel system could use some attention. I have yet to do so, but hopefully that is all that's left wrong with the truck for awhile anyway...

 

[trueknight]

Took it to the stealership...

Alright so after years of receiving the cruise control wiring TSB about risk of garage fires, I finally take it to the stealership. The first time in the last 6? years. I told them to diagnose the car which they say will cost $110 to check the O2 sensors. After a day, they come back and told me it's some sort of electrical wiring issue and they have to trace it and the diagnostic will now be $220 more ($330 total). I told them that I had previously gotten a DTC for the o2 sensor and they should really check that out. They told me they didn't get any codes from the computer so it can't be those items. Well another day later they come back and say it's a bad fuel pump and it's gonna be $964 to replace it. A bad fuel pump would give me trouble anytime I start it and anytime I'm on the road right? I'm only experiencing this on warm/hot starts and after I let the truck sit for about 45 minutes, it'll start up fine again. Then the other day, ModT posted this:

http://www.explorerforum.com/forums/showthread.php?t=335823

and now I'm fairly certain of the issue. Any ways, I told them to change all 3 o2 sensors (They told me there was only 3, not 4) before we discuss about the fuel pump so I'm waiting today to see what happens.

If this is the case, I'm going to kick myself for taking the explorer in to do that tsb and letting them diagnose it. I could have changed the o2 sensor myself instead of spending nearly $500.