idling issue driving me nuts!!! help!!!

[shart]

Hey everyone,
I have a 99 expedition 5.4 with an idle issue. Car starts normal but when it warms up rpms drop to 600. I had codes for both o2 banks lean. So far I've done the following: replaced IAC, cleaned maf sensor, replaced vacuum lines at the pvc y connector, checked pcv, checked egr sensor and vacuum tubes connecting to it. Still have the issue!! Any ideas what to check next? I don't hear a hiss at all so I don't think its vacuum leak. Any lines that are known to leak I can check? Driving me nuts!!

 

[2001Expy]

It could be a miss starting. From the COP's, which makes it idle a little funny. It won't throw a code until its truely missing.

 

[jrjr]

One way to check for leaks is to spray some carb cleaner around vac lines and intake gaskets, etc. Go slowly and methodically. Idle will change if you find a leak.

 

[toms89]

Idle is supposed to be around 650 + or - in gear and 730 in neutral + or - warm? When you first start vehicle it will idle higher for a predetermined amount of time. Accessories (a/c) and load will make it vary. What rpms were you expecting?

As far as the 02 sensor lean codes some things that come to mind.. could be vacuum leak as mentioned, weak fuel pump, clogged fuel filter, exhaust leak ahead of 02's or just bad O2 sensors.

 

[shart]

Idle is supposed to be around 800 to 900...600 is not normal and nothing below 800, def is not normal... its so low it might stall out. The chances of an o2 sensor in each bank going bad at the same time is.1 in 5654467544656 million.
I was thinking about COPs, but I'm pretty sure that's not the reason.

 

[Explor2Exped]

hmm... When I did the TPS mod my 98 EB idles around 600...

 

[toms89]

Idle is supposed to be around 800 to 900...600 is not normal and nothing below 800, def is not normal... its so low it might stall out. The chances of an o2 sensor in each bank going bad at the same time is.1 in 5654467544656 million.
I was thinking about COPs, but I'm pretty sure that's not the reason.

OK... went into the stock program for my 2000 expy and checked and Idle drive is set @ 615 and idle neutral set @ 700. It has an adder for coolant temp set at +152 rpm when below 90 degrees coolant temp. THe adder drops to 0 when above that. There are alot of details I am leaving out but it should be very close to these figures when warm. Don't know what else to tell you.

As far as both O2 sensors going bad at the same time...I missed the part where the failed simultaneously. O2s can go bad progressively over time and not have a hard failure. I was just trying to mention potential failures. You are obviously either getting unmetered air in, not enough fuel or the sensors themself are bad. If you have a missfire it should read rich...

 

[RedExpy]

this is a great forum...however one question I do have is... I just changed my oil and also the cam position sensor (idiot light came on).... when I start it now.. it rev's for about 2K, then idles as it warms for about 20 sec's.....

any ideas???

 

[toms89]

this is a great forum...however one question I do have is... I just changed my oil and also the cam position sensor (idiot light came on).... when I start it now.. it rev's for about 2K, then idles as it warms for about 20 sec's.....

any ideas???

this is a great forum...however one question I do have is... I just changed my oil and also the cam position sensor (idiot light came on).... when I start it now.. it rev's for about 2K, then idles as it warms for about 20 sec's.....

any ideas???

If it only occured imediately after changing sensor I would double check the electrical connection at the sensor and make sure it and the o ring has seated properly.

You could try reseting computer if you did not do so. I disconnect battery then turn lights on and crank ignition just to guarantee the ecu is completely drained of power. Just dont forget to turn lights and ignition back off before reattaching battery cable.

Don't have any ideas otherwise unless you inadvertently disturbed something else in the process of changing the oil and sensor.

 

[shart]

I did some research and it does some like expeditions do idle around there... Sorry, ive never seen a car idle like that without something being wrong.. Any car ive ever had or worked on has been around 800 - 900... Guess thats just how the expeditions are set. Well the Service engine light is off atleast now and it seems a little smoother then it was so as long as it doesnt dip below 600 ill take it as a win.