Why won't my TBI 350 run right??

[AuroraGirl]

It sounds like you have a few things going on there. It sounds and acts like you have a massive vacuum leak. I would suggest getting a can of something flammable like brake or carb cleaner and spray it around to see if you get a sudden surge in RPM or a smoothing out when you spray a certain area. I would also say that you should check TPS voltage and MAP voltage at idle.

The injector spray pattern wasn't visible in your video and it looked like it was dripping. This usually indicates that you have dirty or clogged up injectors. It should be a fine mist in a cone pattern. This could also be causing the surge

Propane torch unlit is great for it

TPS Is my gut reaction being its a lean in and then bam at once, that to me sounds like a sensor deadspot where the computer gets a little dizzy because of the dropped signal, then instantly comes back at a higher voltage than it would have if it was smooth. if you have a dvom power, set it to record high lows on voltage and probe the wire for TP sensor that varies with pedal and slowly closed to open, maybe twice. then try a brisk if you have no erronous data, and then try snaps of throttle. you would be looking for over 5 volts or negative readings or just below minimum value too. also confirm the throttle cable is tight and no play, that can confuse TPS operation when there is a slack that the sensor wont read but the plates may be opening or somehing like that, confuses the limited electronics.

 

[AuroraGirl]

okay so it does have a working check engine light, which i bought with it on and turned off when i replaced the oxygen sensor. I have replaced the MAP sensor and it is indeed hooked up. I'll have to see whether or not my dad has the hookup for my truck, he's a mechanic of over 30 years and has been helping me along the way, but hard to get ahold of at times. Vacuum leaks, now i said that it may be the injectors spraying, as that's what i'm 99% sure the noise is coming from, does it make such a noise? or is an actual leak nearby that'll need carb cleaner sprayed to check for idle change?

And you're thinking my throttle issue is computer related? would've been my last guess with an '87. Hoped to avoid things like that but i guess i just had to get the dang TBI! haha

Thank you for your words

also you dont need a tool for the light. you can jump the 2 pins to count flashes. no light doesnt mean there arent any codes but its less likely to be severe or pertinent if it wasnt. but worth noting. a scan tool like a tech 1 would give you very limited data stream and not much more likely. a tech 1 or tech 1a or a high level actron from back in day or a aldl computer program would be needed. old stuff. a cylinder balance test is likely one of the only things the tech 1 could do.

The throttle position sensor, esp if original, were not very reliable from GM until the mid 90s when they became standard sensor reliable. Id almost wonder if this truck had its idle messed with and if it had any PROM updates. there is very likely an updated PROM available somewhere for that ECM

 

[AuroraGirl]

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[AuroraGirl]

here are three more TSBs that had more than one page. and pictures

 

[Powerhouse Ranch]

@AuroraGirl, all EXTREMELY helpful, will get back to that.

Before i get to that, does anyone know their way around a Muncie SM465?

 

[AyWoSch Motors]

Before i get to that, does anyone know their way around a Muncie SM465?

Ehhh, a little. No expert, but I now a few things. Whatcha looking for?

 

[Powerhouse Ranch]

Ehhh, a little. No expert, but I now a few things. Whatcha looking for?

So my current dilemma: my speedo/odo hasn't worked for quite some time now, but it did for a few months when i got the truck. Put it off due to having to remove drive line, crossmember, yoke, etc. So i took the tail housing off of the old SM465 (also replacing the leaking output shaft seal) and i'm looking at the speedo gear. You probably know this but i'll break it down anyway. On that tail housing the speedo cable connects and there's a little gear on it. Now i checked the cable originally front to back and it's all good. The gear i described is also all good and it spins as it should, freely. Now the gear it makes contact with sits on the output shaft against the outer bearing. Now i grabbed the gear and pulled it off and held it in my hand, thinking: should this come off this easy? So i asked the old man his opinion and he believes that there should be lock washers or washers holding the gear tight against the tranny, in place. I figured the yoke would tighten it against it when installed but perhaps there is some room to move. But there wasn't any washers when i disassembled, and no signs of broken ones in the drained fluid. BUT IT WAS WORKING?!?! So i'm led to believe that it is missing these washers to hold this gear into place, so the speedo gear can make constant, direct contact.

I think the washers i'm missing are the ones 38 and 39, do we agree? Where could i find these? Any videos showing a SM465 output shaft disassembly and this gear/washers? Appreciate everyone's two cents! Thank you

then again, looking at it perhaps those clips/washers are for the outer bearing, as the speedo gear isn't pictured, due to some being in the t-case. hmmmmm what a mind boggler.....

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[AyWoSch Motors]

So my current dilemma: my speedo/odo hasn't worked for quite some time now, but it did for a few months when i got the truck. Put it off due to having to remove drive line, crossmember, yoke, etc. So i took the tail housing off of the old SM465 (also replacing the leaking output shaft seal) and i'm looking at the speedo gear. You probably know this but i'll break it down anyway. On that tail housing the speedo cable connects and there's a little gear on it. Now i checked the cable originally front to back and it's all good. The gear i described is also all good and it spins as it should, freely. Now the gear it makes contact with sits on the output shaft against the outer bearing. Now i grabbed the gear and pulled it off and held it in my hand, thinking: should this come off this easy? So i asked the old man his opinion and he believes that there should be lock washers or washers holding the gear tight against the tranny, in place. I figured the yoke would tighten it against it when installed but perhaps there is some room to move. But there wasn't any washers when i disassembled, and no signs of broken ones in the drained fluid. BUT IT WAS WORKING?!?! So i'm led to believe that it is missing these washers to hold this gear into place, so the speedo gear can make constant, direct contact.

I think the washers i'm missing are the ones 38 and 39, do we agree? Where could i find these? Any videos showing a SM465 output shaft disassembly and this gear/washers? Appreciate everyone's two cents! Thank you

then again, looking at it perhaps those clips/washers are for the outer bearing, as the speedo gear isn't pictured, due to some being in the t-case. hmmmmm what a mind boggler.....

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That's very possible.
I'm not that familiar with the inner workings, never had that particular transmission part. Only gone as far as changing a cable.
That sounds like it may be the issue. If the washers did fall off, then they didnt go any where, they're probably in the bottom. To cure your suspicions, you could take off the inspection cover, and feel around in the bottom of the case to see if they're there.
It's possible too that the actual gauge broke. Might be the spring on the back of the gauge broke.
You can take the trans side of the cable, put the square line in the chuck of a drill amd spin it. It the gauge doesnt move, you know it's that.
Also I'm assuming by your description, that it's a 2wd. I am not familiar at all with the workings of 2wds, have only ever had 4wds.

 

[AuroraGirl]

@AuroraGirl, all EXTREMELY helpful, will get back to that.

Before i get to that, does anyone know their way around a Muncie SM465?

Well its rather intimidating but I found left to right is easier than right to left. I found the number of steps I take are even that way instead of odd, and prime numbers are intimidating so Id rather just not go there.


Joking aside, no, I wouldnt be an expert. is there an issue with it? What t case you have, know the year? there is the 2 common 4x4 ones, a 10 spline and a 32 I believe spline maybe it was 39... 32 sounds right.. 34? idfk. The 10 spline were used until the 82-84 if I recall the bucket learnings right with the 32 spline adapter for a np205 being different and wouldnt mate to the 10 without some work im sure. The one in my truck right now is an 85-86 which would be the more splines, but I do believe that meant hydraulic clutch(but could be wrong) and I have a linkage setup since 1980, but im not sure other than clutch fork the differences bellhousing side of things, the truck obv a lot.
THere was a rare subset of aluminum top housings that were lateeeeeee trucks early gmt400 possibly. The pto covers are standard 6... inch? bolt? The sm465 also doesnt have a parking brake on the back of it like a sm420 could. The shifter is really sloppy. Like, wiggle neutral check is rather hard to distinguish from any-gear-engaged-and-wiggle test which i think is a more worn than most shifter bushing thing that this guy made a video on how to really tighten it up so its more good:

xc_hide_links_from_guests_guests_error_hide_media

this is the one in my truck, the knob is a 1980 knob I think. It was readable and on my original sm465 so I put it on.

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here are two 10 splines also nearby the 205s for them. if you are meaning 2wd ones, i know very little about them, but tell us what you seek in wisdom. basic facts about them is probably not what you were needing as much as repairing or perhaps understanding operational behavior

On that note, for me, reverse is whiney(reduced with new gear lube, but dont use the synthetic stuff, get the stuff that is compatible with brass and bronze components. older spec. GL5 I think?)

To go into low, it helps to put in 2, slightly engage with clutch, doesnt need to be a lot, then clutch push upward toward low and while holding pressure it usually slides in if it didnt already click over after the first step. 1, 2, 3 are synchronized L and R are not. L is 6.somethin ratio

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i leave you this nugget. I didnt mark it up for this I had it saved recently and it was only that not the blank one lol

 

[AuroraGirl]

So my current dilemma: my speedo/odo hasn't worked for quite some time now, but it did for a few months when i got the truck. Put it off due to having to remove drive line, crossmember, yoke, etc. So i took the tail housing off of the old SM465 (also replacing the leaking output shaft seal) and i'm looking at the speedo gear. You probably know this but i'll break it down anyway. On that tail housing the speedo cable connects and there's a little gear on it. Now i checked the cable originally front to back and it's all good. The gear i described is also all good and it spins as it should, freely. Now the gear it makes contact with sits on the output shaft against the outer bearing. Now i grabbed the gear and pulled it off and held it in my hand, thinking: should this come off this easy? So i asked the old man his opinion and he believes that there should be lock washers or washers holding the gear tight against the tranny, in place. I figured the yoke would tighten it against it when installed but perhaps there is some room to move. But there wasn't any washers when i disassembled, and no signs of broken ones in the drained fluid. BUT IT WAS WORKING?!?! So i'm led to believe that it is missing these washers to hold this gear into place, so the speedo gear can make constant, direct contact.

I think the washers i'm missing are the ones 38 and 39, do we agree? Where could i find these? Any videos showing a SM465 output shaft disassembly and this gear/washers? Appreciate everyone's two cents! Thank you

then again, looking at it perhaps those clips/washers are for the outer bearing, as the speedo gear isn't pictured, due to some being in the t-case. hmmmmm what a mind boggler.....

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On the subject of how it should connect to the trans, I cant use experience esp with 2wd BUT you asked how it still worked. its possible maybe the cable when loosey goosy can make contact but perhaps its able to snake around and not properly stay meshed but perhaps it stays rotating even if its slipping or its putting a lot of force on one spot vs another.

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does this look right

 

[Powerhouse Ranch]

Well its rather intimidating but I found left to right is easier than right to left. I found the number of steps I take are even that way instead of odd, and prime numbers are intimidating so Id rather just not go there.


Joking aside, no, I wouldnt be an expert. is there an issue with it? What t case you have, know the year? there is the 2 common 4x4 ones, a 10 spline and a 32 I believe spline maybe it was 39... 32 sounds right.. 34? idfk. The 10 spline were used until the 82-84 if I recall the bucket learnings right with the 32 spline adapter for a np205 being different and wouldnt mate to the 10 without some work im sure. The one in my truck right now is an 85-86 which would be the more splines, but I do believe that meant hydraulic clutch(but could be wrong) and I have a linkage setup since 1980, but im not sure other than clutch fork the differences bellhousing side of things, the truck obv a lot.
THere was a rare subset of aluminum top housings that were lateeeeeee trucks early gmt400 possibly. The pto covers are standard 6... inch? bolt? The sm465 also doesnt have a parking brake on the back of it like a sm420 could. The shifter is really sloppy. Like, wiggle neutral check is rather hard to distinguish from any-gear-engaged-and-wiggle test which i think is a more worn than most shifter bushing thing that this guy made a video on how to really tighten it up so its more good:

xc_hide_links_from_guests_guests_error_hide_media

this is the one in my truck, the knob is a 1980 knob I think. It was readable and on my original sm465 so I put it on.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

here are two 10 splines also nearby the 205s for them. if you are meaning 2wd ones, i know very little about them, but tell us what you seek in wisdom. basic facts about them is probably not what you were needing as much as repairing or perhaps understanding operational behavior

On that note, for me, reverse is whiney(reduced with new gear lube, but dont use the synthetic stuff, get the stuff that is compatible with brass and bronze components. older spec. GL5 I think?)

To go into low, it helps to put in 2, slightly engage with clutch, doesnt need to be a lot, then clutch push upward toward low and while holding pressure it usually slides in if it didnt already click over after the first step. 1, 2, 3 are synchronized L and R are not. L is 6.somethin ratio

You must be registered for see images attach

i leave you this nugget. I didnt mark it up for this I had it saved recently and it was only that not the blank one lol

it's a 2wd, no transfer case and it has a mechanical clutch, parking brake in rear drums also

 

[Powerhouse Ranch]

On the subject of how it should connect to the trans, I cant use experience esp with 2wd BUT you asked how it still worked. its possible maybe the cable when loosey goosy can make contact but perhaps its able to snake around and not properly stay meshed but perhaps it stays rotating even if its slipping or its putting a lot of force on one spot vs another.

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does this look right

yes???. . . from what i recall yes it does. Like i said, disconnected it from the transmission, put a drill on it and spun, speedo bounced to it's doing it's job. You're saying it's not meshing with the gears right in the tranny? That's what i'm figuring, like it needs some washers to hold that inner gear still. but you're telling me, after driving it, idk, 500 miles when i got it then it stopped working, then a solid 2000 miles straight, not a sign of life from the odo or speedo. How does that happen? no visual signs, no shavings/broken pieces in that portion of the tranny? i am by no means a tranny guru

 

[AuroraGirl]

it's a 2wd, no transfer case and it has a mechanical clutch, parking brake in rear drums also

from what i can tell the trans should have a plastic housing or receptacle that the line goes into on the trans, the cables being standard and perhaps the transmission drive part. but the little box accounting for tire and rear gear differences cheaper and easier than the cables and gears in trans having to be different. maybe. pics of your trans at the gears?

 

[Powerhouse Ranch]

from what i can tell the trans should have a plastic housing or receptacle that the line goes into on the trans, the cables being standard and perhaps the transmission drive part. but the little box accounting for tire and rear gear differences cheaper and easier than the cables and gears in trans having to be different. maybe. pics of your trans at the gears?

i'll have to get that later. work is getting pretty busy for me this week, alot of overtime and i work the 3-11PM, gym and sleeping in the mornings. truck stuff mainly on weekends. i'll follow up then or maybe a sneak a picture tomorrow morning

 

[AuroraGirl]

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I found this but the OP of that poist was unsuccessful in help, but the assumption I got was the these types of units ould use the same trans side gear, use plastic gears for the appropiate ratios, then the cable plugs in. an exception to that would be a cruise system, presumably?