89 bronco idle problems help

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89juice

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:huh:

I have an 89 302 efi BRONCO 90,000 MILES. My idle went up and recently will not come back down. It goes to 1800 RPM comes back to 1600 then goes back and forth. In drive it Idles at about 1200 RPM. I tried IAC changing that out, I tried a new TPS, and adjusting it, cleaned the whole trottle body liberaly, put a new throttle body gasket on, replaced a few qestionalbe vacum lines, PCV valve ....double triple checked vacum lines.......still same syptoms not a lick better. HELP!

 

gatorbronco

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Over the years as your throttle body gets dirty, your RPM's may tend to decrease at idle. If you finally cleaned out all the junk the engine doesn't have to compensate anymore, and your idle can be high. I had the same problem with my bronco on the 302 EFI. Try taking a look at the bracket that is connected to your throttle cable. There should be a small ***** which can be adjusted to change the position of the bracket while you're at idle. You may be able to back this ***** out to reduce your idle RPM's.

In my case, my dad had owned the truck before me. Whenever the idle would be low, he was bending the bracket (I don't know why) to compensate. I finally cleaned out the throttle body and then my RPM's were up around 2,000 at idle. Adjusting the ***** fixed all of that.

 

shift1313

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dont forget you could be pulling air at the fuel injector orings as well if all else fails. try adjusting the linkage first.

you can check the orings at your injectors by spraying some wd or something at the back of the injectors where they seat. if your idle changes you know your sucking air at that point.

 
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89juice

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Pulled the vacum line off of the MAP Sensor .....instantly came down to idle but all other systems went down . Could this be a bad sensor??

 

BroncoJoe19

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Considering all that you have changed, I was thinking that the MAP was the next most likely candidate (after a missed vacuum leak). WHen you pulled the vacuum hose, did you plug it? You may have had a vacuum leak there. Try cutting 1/2 inch off and re-attaching it to the MAP. I know that miesk5 had pointed me to links for testing the MAP, if I get a chance I'll look for them for you.

 
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89juice

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And I did plug the hole on the Map and on the manifold.

Put everything back together then pulled codes today got 11,11.... 9 sec....22,41,33 these were KOEO codes.

 
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BroncoJoe19

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And I did plug the hole on the Map and on the manifold.
Put everything back together then pulled codes today got 11,11.... 9 sec....22,41,33 these were KOEO codes.
You may want to check your grounds.

ALso check that you are getting I think it is 5 volts at your IAC.

 

BroncoJoe19

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Here is a list of grounds for a '92 - '96 bronc

I took a look in my Haynes manual.

They list 10 separate grounds... A-J.

A. Starter mounting bolt

B. Right front of Engine compartment near the battery

C. Lower left front of engine

D. Right front of engine compartment on upper radiator support.

E. Left front of engine compartment Upper radiator support

F. Bottom of cowl panel

G. Rear of left fender apron

H. Behind bottom of right cowl panel

I. Left rear corner of cargo area near rear lamp assembly

J. Under center rear of vehicle on rear cross member.

Funny I was just thinking that if not a vacuum leak, it sounds liek your IAC, which you replaced. BUT if it isn't getting the proper voltage from the PCM, IF it wasn't properly grounded, or the PCM wasn't properly grounded, that would cause the IAC to fail, even if it was good and new.

Now that you have multiple codes, they could be from a more central source.

What are your thoughts?

 

black beauty

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did you try replacing the throttle cable? mine did the same thing as far as sticking high then coming back down. the old cable being dirty wont let the spring push back to normal idle right away like it should. try that of someone has not already suggested it or if you have not already done it

 

jsomedaysoon

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Here is a list of grounds for a '92 - '96 bronc
I took a look in my Haynes manual.

They list 10 separate grounds... A-J.

A. Starter mounting bolt

B. Right front of Engine compartment near the battery

C. Lower left front of engine

D. Right front of engine compartment on upper radiator support.

E. Left front of engine compartment Upper radiator support

F. Bottom of cowl panel

G. Rear of left fender apron

H. Behind bottom of right cowl panel

I. Left rear corner of cargo area near rear lamp assembly

J. Under center rear of vehicle on rear cross member.

Funny I was just thinking that if not a vacuum leak, it sounds liek your IAC, which you replaced. BUT if it isn't getting the proper voltage from the PCM, IF it wasn't properly grounded, or the PCM wasn't properly grounded, that would cause the IAC to fail, even if it was good and new.

Now that you have multiple codes, they could be from a more central source.

What are your thoughts?
i know its a little off topic but i've looked my haynes manual front to back and i cant find the list of grounds for my truck. i've got two mid 80's trucks. where exactly do i look for the grounds list?

 

BroncoJoe19

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Unfortunately although my version of Haynes lists a different wiring diagram for every couple of years

ie 1980, 81-83, 84-86, 87-89, 90-91, 92 and later. The only instance of giving actual ground locations is in the 92-96.

I have a '90 EVTM and will post what they have for a '90

 

BroncoJoe19

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Ground number and locations in 1990 Bronco EVTM

G100 LH side of Radiator support

G101 RH side of Radiator support

G102 RH side of Radiator support

G103 LH rear side of engine, near knock sensor

G104 LH rear side of engine compartment, near electronic engine control (EEC) module, on the left fender close to the firewall

G105 LH Side of engine

G106 RH fender apron, near voltage regulator

G107 RH fender apron, at starter relay

G108 RH fender apron, at voltage regulator

G109 RH fender apron

G201 LH rear side of I/P (looking at the diagram it is at the bottom of the driver's side dash assembly. Screwed to the bottom edge, just to the left of the steering column. It is the ground for the instrument cluster)

G202 Behind RH cowl panel

G203 RH rear side of radiator support

G204 On steering column

G205 Behind Center of I/P (Dash), near speed control amplifier

G400 LH side of cargo area, near rear light assembly

G401 Below LH side of cargo area, near crossmember

G500 Inside driver's door, near left door speaker

 
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89juice

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Went to the parts store replaced the map sensor..... no change..... checked all grounds all look good also removed some and took steel wool cleand up ....still no change. Also sprayed carb cleaner around injectors no change in engine speed. I am about to pull my hair out I have no idea whats going on.

 

BroncoJoe19

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Q. Why is your handle 89juice?

A. I have an '89 bronco that is making me loose my hair...

Q. yeah... and the juice?

A. the juice is how I take my Rogain.

I am really sorry to hear that you have to take Rogain.

What other symptoms do you have? Do your brakes work as well as before? Could it be a vacuum leak in the vacuum booster? Perhaps you can try to clamp off the vacuum hose that goes to it.

Do you have cruise control? Does it work? There is a vacuum dump solinoid/switch - that could be defective.

 

4x4mexicano

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What about your intake gaskets? I have a 351 in my bronco with the same problem and it ended up being a bad intake gasket which was letting in way too much air.

 
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89juice

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A: My name is 89juice because my bronco is white.

Yes I have checked clamping off the vacum to the brake booster again there was no change. The brakes work same as before. It does have cruise control, but it does not work. I also tried plugging all vacum lines to the cruise modual... again no change.

 

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