elevated idle on startup, normal?

[jrowe6]

just wondering if its normal for my idle to go up to like 1400 on startup, then slowly fall down to about 1000ish. otherwise the engine runs good, idle can be a bit shaky but i dont expect much more from an engine with 205k on it. its just that every time it starts, hot or cold, the idle seems high at first and for longer than most cars. and also, if its in neutral and i rev the engine it falls back down to the proper idle very slowly, especially from 1500 on down to where it stays.

 

[jrowe6]

99 ohv

it has done this the whole time i have owned it, which has been for the past 30k miles. i have replaced the plenum/upper manifold gaskets, just put new plugs in, replaced the wires a year or so ago, replaced the fuel filter a year or so ago, new maf a while back, new iac.

no codes or CEL

 

[alohamonte]

So cold startup is 1400 then it settles to 1000 when warm? Is that in park or drive?

My 98 OHV is much lower, maybe 500-600 warm in drive. 1000 warm in drive is way too high.

Consider replacing/cleaning/testing your Idle Air Control Valve and Mass Air Flow Sensor. If that tests fine 3rd on my list would be Intake Air Temperature Sensor.

 

[jrowe6]

those numbers are all in park or neutral. i believe it is in that 6-700 range in drive. i think i will make a video and post it. much easier to see than to explain in words.

 

[jrowe6]

oh and where is the air temp sensor?

i was under the impression that was built into the MAF, which i clean with MAF cleaner regularly.

 

[alohamonte]

1000 in park... I will have to compare to my truck in the morning but that doesnt sound too far off.

It called the Air Charge Sensor or Intake Temperature Sensor and it's located on plastic/rubber intake tube between the MAF and the Throttlebody. I has a wire running to it. Half a twist or so and it will come out of the intake tube. I'd try cleaning it first, but I had to replace mine.

Reference autozone part number #SU2004

 

[ranger7ltr]

Location of IAT depends on MAF plug...

Look at the plug on your MAF sensor... If there are 4 wires going into it then look for the IAT upstream near the throttle body in the air supply tube...

If the MAF has 6 wires going to it, then the IAT is built-into the MAF sensor and it is part of that assembly...

Honestly I don't remember the model year this started but the wire count is the most accurate way to determine where the IAT sensor is located...

And, BTW, on my 99 Explorer it is part of the MAF unit...

I almost forgot the reason for this post...My 99 Explorer will start at 1400-1500 cold fast idle then drop to 700-800 rpm idle after about 30-60 secs...The tach will read higher actually; these numbers are from my scanner...So I would say yours seems to be running within specs...And these numbers are in park...In drive, the idle drops about 100-200 rpm...My truck has done this for the almost2 yrs I have owned it but Fords I have and had owned do the same thing including my v8 Ranger...

There is one sensor that you can check to see if it is getting tired and that is the ECT sensor...Its readings will influence the ECU and help determine the cold enrichment, among other parameters, that the engine needs to run...

 

[atblue5spzx3]

My 95 OHV does the exact same thing.....runs great otherwise.

 

[jrowe6]

what is the ETC?

 

[jrowe6]

i have also been wondering if knock sensors loose accuracy with age, i replaced one on my mothers car which would barely run at all, and it ran quite a bit better with a new one. but hers was cracked and was throwing a code mine is not. i am also fairly sure i need all new O2 sensors, who knows how old they are, and even without throwing a code i would think they are not as accurate as they used to be.

really the engine runs pretty darn good, i am just nit picking now bc i have nothing else to do and would like to do whatever can be done to get this engine running as close to optimum as possible.

my MAF has 6 wires btw

 

[jrowe6]

i am going to make a video right now.

 

[ranger7ltr]

what is the ETC?

You mean the ECT? That is the Engine Coolant Temperature sensor and the resistance values measure the coolant temps and manage the fuel flow, injector dwell, and other parameters as well...

 

[jrowe6]

just made some videos, im going to upload them to youtube here shortly.

as for the ect, could this give the wrong signal and keep the engine running in warm up mode constantly?

 

[jrowe6]

at idle not in gear the engine is shaky and there is mild knocking

 

[SirkXLS]

Mine too! mine does the same idle , and after you drive for a bit. park it. leave it running in park it's fine! Iv'e already changed MAF, IAC and thermostat, nothing yet, but ill let you know if i find the culprit.
Jrowe have you changed oil recently? That's the only difference iv'e made before this and it's started a light knock and you can hear the lifters. Only other idea iv'e got from the guys here would possibly be the bosch plugs i just put in. heard a lot of bad feed on them.

 

[jrowe6]

Mine too! mine does the same idle , and after you drive for a bit. park it. leave it running in park it's fine! Iv'e already changed MAF, IAC and thermostat, nothing yet, but ill let you know if i find the culprit.
Jrowe have you changed oil recently? That's the only difference iv'e made before this and it's started a light knock and you can hear the lifters. Only other idea iv'e got from the guys here would possibly be the bosch plugs i just put in. heard a lot of bad feed on them.

i use different oil pretty much every time honestly. it has mobil 1 full synthetic in it right now. i dont have any valve clattering or anything, just some intermittent knocking. and its not like knock knock knock knock knock, its just random knocks every so often. and it does not at all correspond to rpms, also the shaky idle goes away once i put it in gear, and the knocks pretty much go away as well.

 

[SirkXLS]

had to make sure you didnt steal my truck lol SAME exact prob, nice to hear someone else this is happening too though, means there must be a certain sensor needs to get fixed. just wish it was throwing a code to help me out but nothing!

 

[jrowe6]

http://www.youtube.com/watch?v=rwwdoHTGnR4

cold startup

 

[jrowe6]

had to make sure you didnt steal my truck lol SAME exact prob, nice to hear someone else this is happening too though, means there must be a certain sensor needs to get fixed. just wish it was throwing a code to help me out but nothing!

it might take me a while but i will figure it out. stay tuned

 

[jrowe6]

http://www.youtube.com/watch?v=G1qggKzGdII

warm startup