93 explorer starts, will not idle

[fearsome]

I am the proud owner of a 93 explorer sport. My problem started one day where the idle dropped to about 500 rpm and to get it home I had to do the one foot on the gas, one foot on the break trick. It would barely idle and had no power when I used the throttle.

I have replaced both o2 sensors, the IAC valve, TPS, FPR, cleaned the MAF filaments, and cleaned the spark plugs. There was no change in its condition until I changed the last o2 sensor. Now, the explorer starts fine, revs up and runs, but when it kicks down to idle it dies. I can hear the fuel pump prime before starting and it also primes just after the engine dies now. It will not run on its own at all.

I was pulling codes earlier and they all indicated that the o2 sensors were to blame. Does anyone have any ideas? My wife and I have been sharing one car for 2 months now and it is getting old.

 

[MrShorty]

Did you clear the CM codes after you replaced the O2 sensors? Are you getting O2 sensor codes in the KOER test? What codes are you getting from each test?

 

[fearsome]

I also have a post on this from earlier in the 911 section. I didn't know if it still belonged there since it is an on going issue. I'll just keep that one going, especially since MrShorty is replying there also. Thanks and sorry for the double post.

 

[adale]

have you checked the fuel filter and does this do this at all temps?

 

[Az_NavajoRob]

Something else to think about-how's your fuel pressure? My old '86 Ranger would occasionally buck and skip under acceleration and I tried replacing the fuel filter but to no avail. It only did it once in a while so I didn't worry too much about it. Then my fuel gauge started acting up so I pulled the fuel pump unit out of the tank to check the float. Not only was the float full (had a pinhole) but the fuel line going from the pump to the bulkhead fitting was so "crusty" that it practically disintegrated to the touch. If it weren't for the fact that the old Rangers had a second external pump, I don't think it would have run at all. Just something to think about.

 

[MazdaGreg]

The idle being at 500 really points to the IAC. Is that a factory IAC valve? My brother has a 93 ranger with the 4.0 and he had gone through at least 3 of the Autozone IAC's. He would never set a code either. Normally happened after he would spray off the engine. I would at least try another IAC if the idle won't change. This is beside the obvious, just make sure that there are no codes for any other issues.

As far as the fuel pressure, the regulators on these things do go out, i've lost the one on my Navajo, but they normally fail in the wide open position, to where they flood the engine. you'd just have the rotten egg smell from the exhaust, but the computer would adjust the pulse width on the injectors so it would run halfway decent. That doesnt mean i'd drive it though.

Go back to the IAC and start there.

 

[MazdaGreg]

And i forgot. As far as the o2 codes, i'd adress the idle first. that could be a secondary symptom. those should have no affect on idle, unless you have a Check Engine Light, but even then, it should not idle at 500.

 

[nascar_intimid]

remember to reset the computer after your fix it could still be acting on the old fault

 

[MrShorty]

And i forgot. As far as the o2 codes, i'd adress the idle first. that could be a secondary symptom. those should have no affect on idle, unless you have a Check Engine Light, but even then, it should not idle at 500.

I am of the opposite opinion. O2 sensors have everything to do with fuel mixture, both at idle and at speed. The only time the O2 sensors aren't used is when the engine is first started, because the sensors are too cold to function. Once they are warmed up, the computer uses them to get the correct fuel mixture. Incorrect fuel mixture will cause poor idle.

 

[MazdaGreg]

I agree, if the o2's are telling the truck to lean out, of course it's gonna idle rough. that will be due to intermittent misfire's within the combustion chamber. I was saying it has no affect on idle speed. That is determined by a preset program within the pcm. It should do all it can to keep it around 750 or 800, depending whether it's an automatic or standard transmission.

And if o2's are that far out of range that it's leaning the truck out, or richening it up, it will set a code, and the computer will jump out of closed loop, into open loop, and they will be ignored anyways.

 

[Big_Leo]

Check The Idle air control. its a bolt on part about $70. controls the engine idle speed! solved the problem on my 97 SOHC