normal idling rpm? + other questions

[dwalin]

hello guys, have a question here. i've got a 4.0l ohv engine in my '96 truck, and tachometer reads just a bit lower than 1k rpm when idling, i guess that means about 900 rpm or so. other X owners here say they've got about 500 rpm idling, but most of these trucks are gen1. but afaik my ohv engine is the same as in gen1 so i guess i should get 500 rpm too.
decided to try and tackle with this myself, cleaned maf and idle control using hi-gear carb cleaner. no luck, still just a bit less than 1k rpm. what to do next? besides changin 'em spark plugs and wires, scheduled to next payday in may.
second one, i want to change all liquids after this harsh winter (it was -29F as i recall, X groaned but cranked), is it safe to use syntetic oils and atf? some say i shouldn't, because it will leak out, other say go ahead -- i'm lost. now i'm running texaco havoline half-synt 5w30, changed it last december. as for tranny and rear axle and transfer case, i just don't know -- bought the truck last autumn and was too dummy then to do anything. will the change to full synt improve my mpg? the highest i've got yet was 13. i guess the local traffic doesn't do any good to improve mpg, traffic jams are awful... but still.
third one, just to make sure: am i right thinking that there's one catalytic convertor on my truck? how do we have two oxy sensors then? there's something i can't understand.
four one, it's driving me nuts: when accelerating rapidly, sometimes i hear muffled "thump!" somewhere in front and below, and the same thump but louder appears when i'm braking any harder than very slowly. not all the time, though. what could it be? i fear it may be tranny.
sorry for stupid questions and thanks in advance.

 

[Viper81]

about your idle, when is the last time you changed your belt? i had the same problem on one of my older cars and it turned out that my belt was way too tight. if not that then check all the pulley's and make sure that they are not warped or crooked. you could also check to see if you have somewhat of a restricted airflow. bad air filter maybe? i dont know. just shooting some ideas out for ya. good luck.

 

[cybergasm]

Well when warm mine also idles at 900 rpm or least that what the tach says buy i when i put it in gear then drops closer to 500 or so. So i think on that end u got nothing to worry about. ( I got a 99 OHV)

Synthetics i don't see a prob with going with them as long as motor, trans etc are tight and not leaking it they are then i would'nt waste the $$ then
if it's going to leak becuase of a bad gasket or ? Mileage gains don't know about that since i have not tried them my self.

Cats could be possible to have just one I know under my 99 i have 4 of em!
Gotta love US emissions control as far as oxygen sensors i know i got two of em think it has something to do OBDII diagnostics somebody else might have a better answer than me.

Thump have no idea about that somebody else might me able to help.
hope i was of some help
BTW welcome to the forum!!

 

[budwich]

My 96 also idles in and around that 900 (just less than 1K).... seems high compared to other vehicles that I have owned. I was thinking my thermostat runs a little cool resulting in the truck "thinking" its cold and thus running a bit rich / fast. Tried changing the therm... helped bring up the motor temp a bit but it still seems to idle high but overall it is fine.

 

[dwalin]

about your idle, when is the last time you changed your belt? i had the same problem on one of my older cars and it turned out that my belt was way too tight. if not that then check all the pulley's and make sure that they are not warped or crooked. you could also check to see if you have somewhat of a restricted airflow. bad air filter maybe? i dont know. just shooting some ideas out for ya. good luck.

i've never changed the belt myself but it seems to be in good condition. as for adjustments, last winter i had an accident of a sort when the idler pulley didn't survive the cold and was torn off completely. was replaced at the shop and guys there did the adjustments so i think it must be in order, otherwise they'd say about it.
as for air flow, i did clean the maf today and checked air filter while i was at it. it's not new but was replaced in december, along with engine oil. in february i got in a crash and then didn't drive for two months so i assume it's not ready for replacement as yet. didn't check the throttle body but think i should take a look at it. the intake hose itself looks pretty clean, all to my surprise.
thanks for the suggestions, though. it never hurts to take in all ideas and check the most obvious things. as one of my college teachers said, not one of the nobel prizes was awarded for obvious things.

 

[dwalin]

Well when warm mine also idles at 900 rpm or least that what the tach says buy i when i put it in gear then drops closer to 500 or so. So i think on that end u got nothing to worry about. ( I got a 99 OHV)

well, when i start the engine it gets as high as 1500 rpm for a warm-up, then slowly drops to 900 rpm. when i put it in gear it doesn't drop. and while i'm driving, it never drops below 900 rpm. though recently the tachometer started to behave irratically, when idling it can drop to 500 rpm or even lover and then spring up to "normal" 900 rpm but the engine sound never changes so i guess it's the tachometer itself. shoulda take a look at it somewhen.

Synthetics i don't see a prob with going with them as long as motor, trans etc are tight and not leaking it they are then i would'nt waste the $$ then
if it's going to leak becuase of a bad gasket or ? Mileage gains don't know about that since i have not tried them my self.

well i have read the aldive's quest for 30 mpg thread all through and got impressed. i don't do highway driving very much and sincerely i can't call my driving a city cycle because it's a traffic jam all the way, i drive about 25 miles from home to the office and it takes me two hours on the average to get there. but gas prices are hurting so i'm trying to think up all the inexpensive ways to improve mileage. if i understand it properly, changing all fluids to full synt is one of those inexpensive ways. and it lasts longer between changes, another advantage.

Cats could be possible to have just one I know under my 99 i have 4 of em!
Gotta love US emissions control as far as oxygen sensors i know i got two of em think it has something to do OBDII diagnostics somebody else might have a better answer than me.

aah, well i'm not in the u.s. so your emission control rules do not apply here. but this year they're forcing euro-2 on us with euro-3 and euro-4 just ahead in '8 and '10 so i think i shouldn't just shed the cat as many other do, replacing it with a steel pipe. and oxy sensors, i thought i have three: one before cat and two after. i just don't understand: either there are two cats and two sensors after them or one cat with two sensors. gotta clarify, because i did scan engine comp codes and it says "after cat second bank oxy sensor failure". judging from the noise my engine generates, it seems that i lack a cat. ;(

Thump have no idea about that somebody else might me able to help.
hope i was of some help
BTW welcome to the forum!!

thanks, great forum. very helpful.

 

[dwalin]

My 96 also idles in and around that 900 (just less than 1K).... seems high compared to other vehicles that I have owned. I was thinking my thermostat runs a little cool resulting in the truck "thinking" its cold and thus running a bit rich / fast. Tried changing the therm... helped bring up the motor temp a bit but it still seems to idle high but overall it is fine.

aah, so i'm not the only one. thanks for the idea, i do think my thermostat is nutty because last winter it took just too long to warm up inside the truck, and i had my climate control set to max heat. maybe changing it would help.
by the way, talking about thermostat -- how's your engine temp gauge reads when engine is warmed up? mine's showing somewhere between 3/4 and 2/3 on the left side, not even near the half of a scale. i've always thought the operating temp should be somewhere around 1/2...

 

[budwich]

ya.... my temp was usually near the bottom (1/4 ish) of the way up the scale. With the replacement therm, its a little higher but still not near the middle where I would expect it also. There is another thread on here about others indicating that there temp is on the low side. I have only owned my first ford for less than a year and was previously basically a GM kind of guy. I recently fixed our Olds which also had low temp (and reduced heat) and significantly reduced gas mileage. After replacing the therm, temp is "rock steady" near the middle on warm up and the gas mileage has gone way up to normal / better than ever.
My ex isn't throwing any codes and passes emission tests but I think it is running a little fast in idle and I think its a bit rich thinking its still cold.

 

[No1dan2001]

Hope this helps. on the intake of the OHV engine, there is a small thing right where the intake manifols meets the intake. its a small thing, about 1.5-2 inches in length, cicular, with a black plastic tip. i forgot what its called, but while the engine is runnung, try to tap it with a screwdriver. if your idling changes, then i'd replace it. My next door neighbor has a 96 xlt OHV and i took a look at it for him and it turned out thats what it was. If i can think of what it's called ill post it.

PS as stated in my signature, my tranny just died on me...about 3 weeks after it started clunking....hopefully you will have better luck. You might wanna check the trans mounts??

 

[dwalin]

ya.... my temp was usually near the bottom (1/4 ish) of the way up the scale. With the replacement therm, its a little higher but still not near the middle where I would expect it also. There is another thread on here about others indicating that there temp is on the low side. I have only owned my first ford for less than a year and was previously basically a GM kind of guy. I recently fixed our Olds which also had low temp (and reduced heat) and significantly reduced gas mileage. After replacing the therm, temp is "rock steady" near the middle on warm up and the gas mileage has gone way up to normal / better than ever.
My ex isn't throwing any codes and passes emission tests but I think it is running a little fast in idle and I think its a bit rich thinking its still cold.

a-ha, so the thermostat is one to be scrutinized at the first opportunity. thanks for the suggestion, and after looking up its price i think i'll just change it at next service. $30 for the part and labor for replacing, i guess i can afford that.

 

[dwalin]

Hope this helps. on the intake of the OHV engine, there is a small thing right where the intake manifols meets the intake. its a small thing, about 1.5-2 inches in length, cicular, with a black plastic tip. i forgot what its called, but while the engine is runnung, try to tap it with a screwdriver. if your idling changes, then i'd replace it. My next door neighbor has a 96 xlt OHV and i took a look at it for him and it turned out thats what it was. If i can think of what it's called ill post it.

if i got you right, this thing is motor idle control sensor. i'm aware of it and just cleaned it up last weekend. by the way, life proved that this thing is quite important and not always should be replaced if malfunctioning. sometimes it's enough to clean it well with a carb cleaner or something. i bet money not many people are aware of this thing at all and you'll be amazed to see how much **** it accumulates and how it affects driving. almost the same as cleaning the maf unit.
however, sometimes it must be replaced... but i'd rather avoid paying $100 for such a small piece of hardware.

PS as stated in my signature, my tranny just died on me...about 3 weeks after it started clunking....hopefully you will have better luck. You might wanna check the trans mounts??

*sigh* i know i have better luck because i'm driving my X for eight months now and it was like that all the time. trans mounts, maybe. the strange thing is, when the thumping occurs, i feel the brake pedal vibrating. i know that this means anti-blocking system is alive and does something but honestly i can't imagine what does it do on normal non-slippery road surface?! it's a mystery to me: i press the brake pedal to decelerate, it goes "thump!" somewhere beneath the body and after that the brake pedal vibrates for a second or two, then stops. mystery...
as for trans mounts, how'd you think, can i check 'em without unmounting tranny?

 

[96limitedX]

my '96 ohv has allways idled at 800-900rpms when warm..around 1,500rpms when cold.

 

[No1dan2001]

as for trans mounts, how'd you think, can i check 'em without unmounting tranny?

I believe so..although you should be able to teat like the engine mount. brake+gas in Drive = Thump or clunking sound most likely means bad mount. i believe...like i said im just goin from previous experience im not a mechanic.

 

[dwalin]

my '96 ohv has allways idled at 800-900rpms when warm..around 1,500rpms when cold.

hmm. so there's a chance that 800-900 rpms are normal for these engines? that's a surprise. i'll try to ask some other gen2 owners...

 

[96limitedX]

lol and my old '95 X and my moms '94 both idle the same too..i forgot to add that

 

[No1dan2001]

hmm. so there's a chance that 800-900 rpms are normal for these engines? that's a surprise. i'll try to ask some other gen2 owners...

If im right i believe the target mark should be 750, but i mean a few hundred RPMs shouldnt make too much of a difference

 

[budwich]

My GM stuff says 700 for auto trans type vehicles (small 6 cylinder). That's what I am kind of use to. I can't find anything on my ford documentation.... all they say is that "it is not adjustable and is electronically controlled". I would say my Ex is nowhere near that... maybe 800 but probably closer to 900. I think it is high but it would appear alot of people have this. I think that this might be an indication of perhaps running too cool (ie. improper thermostat)... that's one of the diagnostic symptoms chart but they do specify any speed. Anyways, I am not saying that it will cause any problems but I think it is reflected in poor gas mileage as the vehicle tries to correct things by enriching the fuel mixture a bit and we all know what great gas mileage an EX gets already... :-(

 

[budwich]

Actually, I just did a search on the net and saw a "spec" for a 2007 ford sport and it indicate 625 in drive for a v6.... that's more like what I am thinking. Anyways, I replaced my IAC about 4 months ago because of the famous moose call and cleaned the maf. It didn't have any effect on the idle but the "moose" is gone.

 

[96limitedX]

far as i know thats the idle speed for the 4.0 OHV..and i get 16mpg in town and 20mpg highway. i like that fact myself..higher idle means alittle more voltage from the alt.

 

[dwalin]

I believe so..although you should be able to teat like the engine mount. brake+gas in Drive = Thump or clunking sound most likely means bad mount. i believe...like i said im just goin from previous experience im not a mechanic.

well, afaik the method you described is also known as a "stall test". i did it once to check how's my torque convertor performing -- too bad it seems but there was no thump. anyway, i feel i'm heading up for a major tranny rebuild...