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Discussion Starter #1
Sorry to start so many threads but I've been working on the Bronco like crazy lately. When I first start the Bronco it is at 2k then slowly drops down to 1k. I've also noticed that between shifts it climbs about 500rpm. So far I've done the follow to try to fix the problem.

-new IACV
-new PCV
-removed both intake pipes on TB and sprayed TB cleaner
-put a small amount of WD-40 on throttle springs

I'm kind of out of ideas :whiteflag

Again, thanks for putting up with my numerous threads and helping me get this Bronco in tip top shape, you guys are the best! :rockon
 

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DISCLAIMER: TALKING ABOUT MY MUSTANG.

I had the same issue with my car, and it turned out to be my tps was out of range. Set it to .995 volts and now step on the clutch the rpms fall to 850 and hold steady. That may be your problem too, or vacuum leaks. Also, make sure the throttle isn't sticking.
 

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1995 XLT SAS w D44 and D60 rear
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Do you think that the issue with the tranny could be the tranny itself? Perhaps worn clutches and the like?
M05 no internal clutches.

Sounds like you are on the right track with the throttle but I am not sure. The RPM at start up sound right with the auto choking.
 

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Roller rockers are gay
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My Bronco has MAF, but it never revs above 1100. Jumping to 2000 RPM is not right. Does it idle at 1000 RPM all the time?
2000rpm at cold start up is perfectly normal for these trucks.

shit, my car even does it, and it's only 5 years old.

OP, check your TPS voltage/ohms.
 

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Discussion Starter #7
Update:
Recleaned the TB extremely well!
Put on a new TPS
I know it has nothing to do with clutch disengagement...

It just loves to jump up to 3 or 4k between shifts? I'm out of ideas. What does the 93 use instead of a MAF?
 

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Does it slam into the next gear or does it kind of ease in. Sounds like slippage in the tranny...but hey I'm old fashion. Maybe it's just the 3m...Mysterious Michigan Malfunction. :banghead I had plenty of those when I lived there..Sylvan Lake.:histerica
 

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Update:
Recleaned the TB extremely well!
Put on a new TPS
I know it has nothing to do with clutch disengagement...

It just loves to jump up to 3 or 4k between shifts? I'm out of ideas. What does the 93 use instead of a MAF?
Sounds to me like a bad vacuum leak. Check your upper to lower gasket, brake booster, PCV, etc.
 

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Just as a matter of routine diagnosis I would "pull codes" from the computer to see what elec/electronic faults are indicated BEFORE throwing parts at a problem.

Clean the IAC = "idle air control" located on the right side of the throttle body, bottom valve part only with TB cleaner and make sure it has alll evaporated BEFORE reconnecting oor you could fry the elec. solenoid attached, rpelace the gasket if need and this should improve idle.

As for the TPS = throttle position sensor located underneath/bottom of the TPS, most of them sold today are the "plug & play" style with no "slots" for physical adjustment so you may have to drill out the mounting screw holes in order to adjust it using a mutlimeter for voltage setting.

In the past the ideal setting was thought to be .93-.97 volts or just under 1 volt but recently someone here posted new information regarding this and it appears the setting should be between .55v-.75 volts.

Posted by FSB member Jermil01:
Wanted to update this thread based on some TPS adjustment information I got from one of my tuning sites. This goes against the conventional wisdom of setting the TPS closer to .95 range. Thoughts??

Regarding any ECU controlled function (and idling conditions in particular), before any strategy based adjustment can be made by a computer controlled system, it must first run somewhat normally in a default and OL mode. To do this with a FORD you must first follow a few rules.
You must keep the TPS input above the deadband area and below the "tip in" area. On a FORD this equates to below approximately 0.9V and above 0.45. Anything above 0.90V the ECU thinks the throttle is starting to open. This brings into affect possible dashpot and fuel cut strategies which can turn one grey real fast. Below approx 0.40-0.45V the system suspects an incorrect input and substitutes a default figure. So first off, the TPS should be set to around 0.55-0.75V.


There is a Ford Racing Performance Parts (Techline (800) FORD788) "idle setting procedure instruction sheet" setps 1-9 which explains how to disconnect and adjust the IAC and drilling out the mounting screw holes in order to adjust the TPS voltage setting, TB blade angle/air induction.

Vaccum leaks in the upper fuel injection plenum, lower intake manifold, valve covers and emissions system can also contribute to high idle so go around and re-torque all bolts and visually inspect all plastic and rubber vacuum lines and repair or repalce anything suspicious looking.

Anther idle issue could be from the crusie control servo where disconnecting it to see if that's the high idle cause is another procedure you can try.

PCV = positive crankcase ventilation filters is another possible source if they're old and cloged up, not expensive but easily replaced I would go with the Motorcraft one.....it's very well made vs the (cheaper) standard brand offered by auto stores where those are mfg'd in either China or Mexico with no quality control AND make sure the PCV filter fits/sits correctly in the valve cover usually the passenger side underneath the upper fuel injection plenum so the vaccum hose routes in/on it properly with out any kinks too avoid a vaccum leak there.

Additional help. www.broncolinks.com and FSB member El Kabong's - "baba loohey's favorite FSB links" and questions

Good Luck ~ :thumbup
 

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Discussion Starter #12
I had vaccum leak on the list of possibilities, however it only happens around 75% of the time. If it was a leak it should do it all of the time at idle. I'm beginning to think it's the throttle body that's starting to go. I've cleaned it as best as I can but it feels like it stills want to hang open or something. I've cleaned and lube its hinge points like 3 times with no luck. I'll still look for a vac leak though...thanks guys
 

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I had vaccum leak on the list of possibilities, however it only happens around 75% of the time. If it was a leak it should do it all of the time at idle. I'm beginning to think it's the throttle body that's starting to go. I've cleaned it as best as I can but it feels like it stills want to hang open or something. I've cleaned and lube its hinge points like 3 times with no luck. I'll still look for a vac leak though...thanks guys
I had not thought about the throttle body sticking, but that is a very real probablility. I am sure someone here has a good spare for dirt cheap!

If not and you have a few dollars to spend, the BBK throttle body works very well.
 

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I've got 2 throttle bodies, the one on there right now was from an 86 BKO part out from an FSB member in VA and it's been on there for several years now without issue, the reason I bought it was the cooling tubes were in mint condition compared to my now original "spare" where the tubes were in poor condition, especially the lower one....TB cost was $30.00 BUT I'm sure you can get parts to rebuild the moving "spring loaded" parts of the TB, no?........

These are simple by design and come apart easily so as long as the TB passages etc. are clean I don't see a functional problem unless it's cracked or damaged affecdting normal operation, a new gasket will help eliminate a vaccum leak just don't over torque the 4 TB mounting bolts and you're good to go..


Good Luck ~ :thumbup
 

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Really? I've never seen any vehicle rev to 2K at start-up.
believe me, it's normal. the colder it is, the higher my cars PCM will command the revs on startup. at 0* it commands around 3k. stupid if you ask me, the bearings are cold, and the oil don't flow for shit.

it idles down to 2k and then eventually to 750rpm once warm.

these trucks are the same way. they rev to 2k or so at start up, give the throttle a quick blip, and it will come down to 700rpm or so. perfectly normal.

Does it slam into the next gear or does it kind of ease in. Sounds like slippage in the tranny...but hey I'm old fashion. Maybe it's just the 3m...Mysterious Michigan Malfunction. :banghead I had plenty of those when I lived there..Sylvan Lake.:histerica
Um, dude, he has a manual transmission.
 

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Discussion Starter #16
UPDATE:

So after a new IAC, TPS, PCV, TB cleaning, lubing throttle plate and cable, I get the idea to simply unplug the IACV while the truck is running and VOILA it's all of a sudden idling dead on and not reving between shifts...seriously?!?!

Obviously I can't drive around with it unplugged, but I guess my question is this...Could the part have been defective out of the box??? OR do I have a deeper underlying issue, like something going on with the harness? I also have been doing some digging, and i screwed up...I messed with the idle screw, ideas how to reset it???

Thanks guys,

Derek
 

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Hmmm - I just replaced my IAC on my '94, the first one i got was bad, it would occasionally fail to go back to idle. And on starting, it would rev to about 2000 RPM for a few seconds, then drop the idle to less than 500 RPM, and bounce back up to about 1000 RPM. The problem with my old one was a wandering idle from about 650 RPM to about 900 RPM.
I got a "Standard" AC 59T, (from Glendale Auto Parts in Livonia) it was made in the USA, so I thought it would be good. After a week, it appeared that the ECM was not relearning the idle speeds, or couldn't control it, so I took it back, they replaced it without a problem, and the new one works, no wandering idle.

So, it could be bad out of the box.

Good Luck
 

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Discussion Starter #18
Correct you were Mikey, I took the IACV back to Autozone and swapped it with a new one...and you guessed it, it's fixed! :doh0715:

If there's one thing I've learned here, it's that PARTS ARE NOT ALWAYS GOOD RIGHT OUT OF THE BOX.

Thanks for everyones help with this matter
 

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DMiller, post #16....""I messed with the idle screw, ideas how to reset it???"


If you had read and "researched" the information in my post #11 it would have answered your question.....it's a very simple procedure.....

This a "baseline" idle procedure where you can disconnect the NEG battery either before or after an adjustment for 15-20 minutes, tapping on the brakes or turn the headlights on/off to purge any remaining current and this will reset the computer to factory defaults.

First, take off the black plastic cosmetic throttle linkage cover to expose the throttle body idle stop screw on the right side, you'll notice it's spring loaded for tension to maintain idle setting and keep from becoming loose and backing out. If you haven't done this before, for reference count the number of protruding "threads" on each side of the idle stop screw going thru the TB block and that way you can put it back exactly the way it was if results are unsatisfactory though I've been using this procedure for some time and never had any problems afterwards.

Warm up the engine to normal operating temp then disconnect the IAC connector and if the engine stalls turn the screw inward one full turn, restart and repeat if necessary until engine will idle with IAC unplugged, reconnect IAC, reconnect NEG battery cable test drive around the block and the computer will learn the new setting. Idle will vary but the idle should satbilize slightly above 500 rpms and below 1000 rpms.

This procedures assumes the IAC is new, or the current IAC's bottom valve has been cleaned and working at optimum voltage level, my suggestion would be to 1st.. disconnect the battery and go with factory defaults and see how it is based on the working condition of all parts etc. or 2nd, if necessary proceed with the adjustment procedure and see if that dials it in.

Check the IAC gasket and replace if necessary to avoid a possible vaccum leak.

Good Luck ~ :thumbup
 

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Correct you were Mikey, I took the IACV back to Autozone and swapped it with a new one...and you guessed it, it's fixed! :doh0715:

If there's one thing I've learned here, it's that PARTS ARE NOT ALWAYS GOOD RIGHT OUT OF THE BOX.

Thanks for everyones help with this matter
Fixed for now.....replace that autozone junk with a motorcraft IAC Valve.
 
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