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Discussion Starter · #1 ·
The warning label on the throttle body said not to clean it but I did and now it's not starting. Cranks over just fine and idled good before I did this. The reason I started messing with it was at speeds 45+ there would be some bucking or hesitation but definitely not transmission related. I had a new Ford TPS sensor laying around so I decided to change it for a shot in the dark. When I took the TB off it was gunked up pretty bad, I threw everything I had at it, Purple Power cleaner, Sea Foam, brake cleaner, came out looking newish. Put in the new TPS sensor and IAC (Ford) for good measure. Cranked it, wouldn't start, I put the old parts back in, still won't start. Checked and verified 5 volt reference at the TPS and voltage climbed on my meter as I manually pulled on throttle cable, everything was within specs. As I understand it, the warning label is there as a precaution because the coating in the actual body might be harmed. I've cleaned plenty of TB's before with no issue so this has me baffled. Did anyone ever hear of a no start resulting from cleaning the TB?
 

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Yo NYFSB,
Was there much gunk in the passageway?
Inspect the throttle body. Check for objects blocking the IAC passage or throttle bore. Excessive deposits, especially on high-mileage engines, can build up in the IAC passage and on the IAC pintle. Excessive deposits can also build up on the throttle plate, so check for a sticking throttle plate.

Check the passages for carbon build up. If they are plugged they need to be cleaned out.
How to Clean and Test your IAC

Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19 @ Code Reader
See my Vacuum leak test in post #11 @ Help with dtc codes and idle
High idle with no applicable codes is usually caused by a vacuum leak,

Other perpetrators are:
Intake manifold leak.
Sticking throttle linkages or throttle body plate is stuck - we had this occur recently! Sprayed throttle body cleaner on linkage atop throttle body and then light coat of WD 40 on linkage. Don't try to lubricate the cable internally.

Throttle Body top view pic in an 88 5.0 by jem270

Speed Control chain is binding, if equipped
Air intake tube is damaged
Throttle body return spring is loose
Throttle body is loose
Idle Air Control Valve (IAC)

"Start the Bronco and bring the engine up to operating temperature. Allow the engine to idle without any driver input to the throttle or pedal. Go under the hood, and disconnect the electrical connector to the
Idle Air Control Valve (IAC). If the engine begins to stubble or stalls the IAC is functional and does not need to be repaired. If the engine idle does not change you should remove the IAC for inspection.

The IAC can pass and still need repair, or it can fail and not need replacing. The plunger and internal spring can get clogged with dirt and oil. This will slow down the air flow and not allow the IAC to function properly. Remove the IAC and clean it. There are 2 halves to the IAC, and you can not buy just one half, but you can take it apart to clean it. But if the internal solenoid is faulty the IAC needs to be replaced." by Ryan M

How to Clean and Test your IAC by Seattle FSB @ How to Clean and Test your IAC

TPS Overview & Testing by Seattle FSB @ TPS Overview & Testing by Seattle FSB @ Bronco Forum - Full Size Ford Bronco Forum
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Mikey350 wrote, "Does your throttle body have a yellow warning sticker that says not to clean the throttle bores?
Try this: Take off the air intake hoses so you can access the throttle bores. Start the engine and place a piece of stiff cardboard over the throttle bores. That should NOT change a correctly configured engine, as the idle air is only from the opening of the IAC, and nothing through the throttle bores.
If that make a difference, then the throttle plates are slightly open due to the removal of the Teflon coating, or the linkage/return spring/throttle stop is screwed up.
If the engine still runs too fast with the throttle opening blocked, try taking off the IAC and blocking those openings.
What you have done is (supposedly) removed all the "normal" air intakes, and if the engine still runs, you have a vacuum leak.
You could then try leaving the air intakes (throttle and IAC) blocked and cap off the vacuum lines coming off the vacuum tree. (except the MAP line) If one of those makes a difference, investigate the leak.
Check the vacuum line from the vapor canister (on the left side of the throttle, when facing the throttle assembly) (cap it, on the outside chance that the solenoid has failed open) (if equipped)
Pull the EGR connection to the intake and plug or cover it. (if you have wide duct tape, use that to cover the hole)
If it still is running with the throttle blocked and the IAC and the lines from the vacuum tree capped, then you have a manifold or PCV line leaking. Plug the PCV line to the intake, then the vacuum line to the brake booster (if it has it's own fitting on the manifold)
 

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Discussion Starter · #3 ·
Thanks Miesk, I pulled one from a pick n pull and it started right up. I ordered a BBK replacement but there on backorder due to Covid. -Teddy
 

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I just stripped down a TB off a 460 I’m rebuilding. Interested if you figure out what was holding you out from starting.
 

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Discussion Starter · #5 ·
I just stripped down a TB off a 460 I’m rebuilding. Interested if you figure out what was holding you out from starting.
I believe it was because port where the TPS connects to was contaminated. I was so fixated on the the blades of the TB being clean that when I disconnected the IAC and TPS I noticed it was full of black liquid residue. That's the only thing I can think of!
 

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‘95 Bronco XLT 5.0 E4OD, MAF——‘95 F150 XL 4.9 M5OD 4x4, SD
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Thanks Miesk, I pulled one from a pick n pull and it started right up. I ordered a BBK replacement but there on backorder due to Covid. -Teddy
Hey Teddy I just came across this same exact issue after cleaning my TB with TB cleaner. So what was it that you pulled off, a whole TB or a single part of it?
 

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Discussion Starter · #7 ·
Hey Teddy I just came across this same exact issue after cleaning my TB with TB cleaner. So what was it that you pulled off, a whole TB or a single part of it?
I pulled the whole TB and replaced it with one from a pick n pull. I am still baffled because when you remove the TPS sensor and IAC the TB is basically a mechanical device and nothing I can think of should case a no start. Except as Miesk stated, some passages may have had carbon build up or some sort of blockage with all the chemicals I threw at it. I would remove the TPS and IAC, make sure everything is clean and dry before reinstalling the sensors.
 

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I pulled the whole TB and replaced it with one from a pick n pull. I am still baffled because when you remove the TPS sensor and IAC the TB is basically a mechanical device and nothing I can think of should case a no start. Except as Miesk stated, some passages may have had carbon build up or some sort of blockage with all the chemicals I threw at it. I would remove the TPS and IAC, make sure everything is clean and dry before reinstalling the sensors.
Well I couldn’t get my tps off, the bolts were/are seized. I tried to keep my TB cleaner off of it as best I could. But I checked it with the meter this morning and it’s almost 1k ohms resistance lower than it should be at closed throttle so I guess it’s gone bad on me. Now to get it off without breaking the bolts... I have a thread for my sort-of resuscitation on my 95 if your interested. It has been a bit of a headache. Lol
 

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Well I couldn’t get my tps off, the bolts were/are seized. I tried to keep my TB cleaner off of it as best I could. But I checked it with the meter this morning and it’s almost 1k ohms resistance lower than it should be at closed throttle so I guess it’s gone bad on me. Now to get it off without breaking the bolts... I have a thread for my sort-of resuscitation on my 95 if your interested. It has been a bit of a headache. Lol
Watched a vid that said to heat up the aluminum with a torch to loosen the Loctite and then hit it with an impact. I used my cordless screwdriver and both came out in one piece. Something to try, but I think they’re #10 screws so good luck.
 

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I got mine back running. I ordered a new tps, cut off the old one, pb blaster and propane torch got the old screw out. Got closest match in metric and standard thread machine screw, turned out to be the metric for mine. 4 x 0.70 I think is what it was. While I had it apart I pulled the intake manifold and cleaned it out along with the TB. Put it back together and it’s all good. Except for the preexisting conditions I have.
 
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