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Old 06-01-2022, 06:36 PM   #1
smith
 
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Default throttle body rebuild?

Any need to tear the throttle body down and clean, new gaskets or o-rings? Mines 30 years old and only been cleaned as a whole. Are there o-rings or just gaskets?
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Old 06-01-2022, 07:59 PM   #2
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Does it run right? I'd so, I wouldn't touch it
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Old 06-01-2022, 09:13 PM   #3
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A small leak I'm looking for. Got a high idle from time to time- under 1000 rpm. Slow to drop down to 750 rpm too. Still testing parts tho. New iac and that companion part. TPS- tested w/voltohm meter and in mode 4 (tps closed). Intake mani gasket, 2 solenoids (leaked), cap, rotor, plugs, wires are relatively new, cleaned egr and new bpt. MAF testing tonight. Just testing everything I can think of.
Seems like a good rev (over 2000 rpms) can kick it down (slowly) most of the time but not always.
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Old 06-02-2022, 03:38 AM   #4
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Quote:
Originally Posted by smith View Post
A small leak I'm looking for. Got a high idle from time to time- under 1000 rpm. Slow to drop down to 750 rpm too. Still testing parts tho. New iac and that companion part. TPS- tested w/voltohm meter and in mode 4 (tps closed). Intake mani gasket, 2 solenoids (leaked), cap, rotor, plugs, wires are relatively new, cleaned egr and new bpt. MAF testing tonight. Just testing everything I can think of.
Seems like a good rev (over 2000 rpms) can kick it down (slowly) most of the time but not always.
It is difficult to get parts for these TBI systems, and the used TBI's you find on eBay are decades old as well.

Aftermarket support is pretty much non existent. If you can't keep the truck going using the existing system, then your only choice is to do the Weber carb conversion. That costs 500 bucks and lowers your gas mileage, and your truck will no longer pass emissions if you live in a state that does that sort of thing.

D21 owners know that if some aftermarket company started manufacturing brand new TBI systems, (no one has yet) they would do a booming business.

Some of the problem with the whole TBI system thing is that when Japanese engineers invented them, they were scrambling to meet the stricter US emissions requirements. And none of them in their wildest dreams thought anyone would be driving these trucks thirty or more years later. You can build a 65 Mustang almost from the ground up using aftermarket parts. Nissan hardbodies have always been kicked to the curb. It's a damn shame.
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Old 06-02-2022, 05:33 AM   #5
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The tbi on my truck was leaking so I decided to use the kit from rockauto. Truck runs better than before and hadn't had a problem since. If you want to try it out then go for it. The kit comes with the gasket and the o-rings. The problem with the tbi is that there is no support for it and it's damn near impossible to get another once without paying outrageous prices. Every time I've been to the junkyard it's the first thing that gets taken from the truck. If the truck is running good I wouldn't mess with it unless you want to have some fun
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Old 06-02-2022, 10:49 AM   #6
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As already stated, it's hard to get parts for the throttle body system, so don't dive into it unless it's necessary.

If you are looking for a vacuum leak, there are several methods to determine where that is. I use Starter Fluid.

With the engine running, you would make short squirts of Starter Fluid in the suspected areas. If the engine RPM increases, you found it. If not, try some other location.

Let one burst of Starter Fluid evaporate before you squirt any more. It is more volatile than gasoline, and it evaporates quickly.
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Old 06-02-2022, 03:33 PM   #7
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My truck shuts off when bottom of air filter holder is moved, with iat sensor still connected. So squirting anything on it's kinda hard to do. Damn thing hides a lot of parts. No kit available tho, not even to look at and see what's in the kit. Not sure if it is a leak, I think it would do it more if it was. That's why I'm looking into electric parts and wires, too. There are some strange parts that can cause electric probs. The neutral position switch is involved with idle air- it's bad-no continuity in neutral. Anyone test the neutral position switch?
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Old 06-02-2022, 04:03 PM   #8
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My truck shuts off when bottom of air filter holder is moved, with iat sensor still connected. So squirting anything on it's kinda hard to do. Damn thing hides a lot of parts. No kit available tho, not even to look at and see what's in the kit. Not sure if it is a leak, I think it would do it more if it was. That's why I'm looking into electric parts and wires, too. There are some strange parts that can cause electric probs. The neutral position switch is involved with idle air- it's bad-no continuity in neutral. Anyone test the neutral position switch?
Gotcha.

OK, on the Neutral Position Switch, the ECU only uses it to detect safety features. It doesn't trim the Air/Fuel ratio any differently when it is or is not in Neutral, like some of these modern vehicles do.

So, you can safely get a short piece of wire and short the wires together, something like I did with my Clutch Inhibitor Relay.



EDIT:

Here's my last picture of a crappy Neutral Safety Switch:



See where the wires are crushed into? You could just twist those wires together, and the ECU would always think that you are in Neutral.

Leave it that way, if you want, or go buy a new switch whenever you have the money.
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Old 06-02-2022, 11:20 PM   #9
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The neutral Position switch does have something to do with the Idle Air Control. Pg. 161 of my FSM lists several things that can affect idle air, thru the ECU. I'm just testing these parts. Just tested the AC switch. So it was just a question if anyone has tested it. Sure mine's not the only one not working and was wondering if others have intermittent high idle because of it.
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Old 06-02-2022, 11:33 PM   #10
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Quote:
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The neutral Position switch does have something to do with the Idle Air Control. Pg. 161 of my FSM lists several things that can affect idle air, thru the ECU. I'm just testing these parts. Just tested the AC switch. So it was just a question if anyone has tested it. Sure mine's not the only one not working and was wondering if others have intermittent high idle because of it.
What year is the Service Manual that you have? I looked in the 1990 version. Page 161 has the KA24e Cylinder Head. EC-161 is the Evap System.

Anyway, you can test the Neutral Position Sensor by simply pushing in that little button on the switch. There should only be an electrical connection when the switch is pressed in.

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