Vince's TBI woes, progressive revelations, and tbi mods.

[Vbb199]

Maybe you have an intermittent issue with the TPS? What about the seal around the throttle blade shaft? Can you wiggle it a bunch? Intermittent issues are the absolute worst things to troubleshoot... good luck man.

Its fixing to get the 46mm tbi, with 81#/hr bbc injectors, and 15 psi.

Stupid worn out ****.


(That is the calculated cfm and fueling i need for my motor based off MATHHHHHHHH)

 

[Bextreme04]

Its fixing to get the 46mm tbi, with 81#/hr bbc injectors, and 15 psi.

Stupid worn out ****.


(That is the calculated cfm and fueling i need for my motor based off MATHHHHHHHH)

Love me some math

 

[Vbb199]

Love me some math

I guess i failed to add, it ALWAYS idles high, intermittently idles like its supposed to


A buddy threw a great idea out.... why not just holley efi swap it... and ya know what.... im getting close.

Input and factual findinga is scarce on the tbi. Lore and redneck mythology is what surrounds them.

 

[Chevyguy]

My TPS ended up causing my idle problems. Had a bad spot in the throttle positioning. Key on motor off and moving the throttle it went from .68 to 1.28 volts on my scan tool. Replacing the TPS fixed my idle problems.

Clayton

Sent from my SM-A705U using Tapatalk

 

[Chevyguy]

I forgot to mention, TPS key on registers .68 volts, and has a smooth transition to WOT with the max output at like, 4.46v.

.68 volts is too high at closed throttle. Should be .45 to .50 volts.

Clayton

Sent from my SM-A705U using Tapatalk

 

[Vbb199]

.68 volts is too high at closed throttle. Should be .45 to .50 volts.

Clayton

Sent from my SM-A705U using Tapatalk

FINALLY some answers.
Ok. I will replace it tomorrow!!! I was suspect if that thing.

I need to remember to tag you when im in search of TBI answers. You, me, and 1987 GMC jimmy are some of the minority of people who like TBI

 

[Chevyguy]

FINALLY some answers.
Ok. I will replace it tomorrow!!! I was suspect if that thing.

I need to remember to tag you when im in search of TBI answers. You, me, and 1987 GMC jimmy are some of the minority of people who like TBI

Glad I could help. I just dealt with some faulty sensors, and broken wiring to sensor connections on my 87 V20. After 33 years the sensors just wear out, and the wiring get's brittle and breaks, or corrodes. TBI is pretty much trouble free and very dependable when it is working properly.

Clayton

Sent from my SM-A705U using Tapatalk

 

[Bextreme04]

The problem with TBI is that it is OBD1 and not very good at that. There isn't enough error checking and reasonableness checks to accurately identify issues when they pop up unless someone has the factory troubleshooting manuals to know what the expected values should be. It makes it very hard to troubleshoot the system when it isn't running right due to an electrical issue. OBD2 has much better reasonableness and error checking and will just directly tell you what is screwed up most of the time rather than just running like hell and never throwing a check engine light.

 

[Vbb199]

The problem with TBI is that it is OBD1 and not very good at that. There isn't enough error checking and reasonableness checks to accurately identify issues when they pop up unless someone has the factory troubleshooting manuals to know what the expected values should be. It makes it very hard to troubleshoot the system when it isn't running right due to an electrical issue. OBD2 has much better reasonableness and error checking and will just directly tell you what is screwed up most of the time rather than just running like hell and never throwing a check engine light.

I know...... my data logger im gonna order will help out with alot of that.

 

[gmbellew]

I know...... my data logger im gonna order will help out with alot of that.

you will be happy. i have aldldroid and a blue tooth obd1 reader. i don't data log, but it is great to check sensor voltages without metering everything, see what the sensors see, see a tach, see temporarily stored codes, etc. i am far from a mechanic, but it was well worth the 20 bucks.

 

[Vbb199]

you will be happy. i have aldldroid and a blue tooth obd1 reader. i don't data log, but it is great to check sensor voltages without metering everything, see what the sensors see, see a tach, see temporarily stored codes, etc. i am far from a mechanic, but it was well worth the 20 bucks.

Does that ALDLdroid work as nicely as they say it does on the app and forums?

 

[1987 GMC Jimmy]

Vince and I were texting, but I’ll
post here so everyone can see my thought process. I agree that the resting TPS value is too high, and I agree with the .5V spec. My only objection is that your Joe Blow TPS from O’Reilly, even a decent one, doesn’t sit at that voltage. Maybe a Delco would, and you can add that to the list of OEM replacement parts that you shouldn’t skimp on. The best I’ve ever been able to get out of a aftermarket sensor is .59V after hogging out the holes, twisting it in the correct direction, and bolting it down. I’d try it. It almost sounds like an intermittently failing coil but not enough that I’d recommend a new one.

As far as the TBI goes as a system, in my experience, it can take a ridiculously long time to diagnose issues. My most effective recourse besides working with a rats nest of diagnostic equipment has been to power through the issue till it breaks completely. Once you work the bugs out, though, it’s great. I’ve been driving the bejeezus out of my Jimmy lately. It’s honestly my best vehicle right now. I could hop in it and drive to Commiefornia and back no problem. Of course, they’d probably stop me at Needles and not let me enter because it’s not even federal emissions compliant. Oh, well. It’s not like I want to go there anyway.

 

[gmbellew]

Does that ALDLdroid work as nicely as they say it does on the app and forums?

yes. it is good. you can set up a variety of screens to see different things or look at all the data in a table format. there were a couple good youtube reviews, if i remember right. you just need the right file for your vehicle. there are others available. i swiped one from a tuning website that shows a little more than the standard ones. but some things are off in it like vacuum hack is off in inches mercury (MAP voltage is right and KPA vacuum is right), injector hack, etc. i am not sure why, but i am not good enough to figure it out. either way, i don't think you would be disappointed.

 

[gmbellew]

Vince and I were texting, but I’ll
post here so everyone can see my thought process. I agree that the resting TPS value is too high, and I agree with the .5V spec. My only objection is that your Joe Blow TPS from O’Reilly, even a decent one, doesn’t sit at that voltage. Maybe a Delco would, and you can add that to the list of OEM replacement parts that you shouldn’t skimp on. The best I’ve ever been able to get out of a aftermarket sensor is .59V after hogging out the holes, twisting it in the correct direction, and bolting it down. I’d try it. It almost sounds like an intermittently failing coil but not enough that I’d recommend a new one.

As far as the TBI goes as a system, in my experience, it can take a ridiculously long time to diagnose issues. My most effective recourse besides working with a rats nest of diagnostic equipment has been to power through the issue till it breaks completely. Once you work the bugs out, though, it’s great. I’ve been driving the bejeezus out of my Jimmy lately. It’s honestly my best vehicle right now. I could hop in it and drive to Commiefornia and back no problem. Of course, they’d probably stop me at Needles and not let me enter because it’s not even federal emissions compliant. Oh, well. It’s not like I want to go there anyway.

if memory serves me right, you can bend the tab on the TPS to also adjust the idle voltage. i think a smooth voltage sweep is probably more important than resting at 0.5v. the gm manuals have a range of allowable voltage that may go to 0.7v, i don't remember.

i second the reliability of TBI. i regularly drive the suburban on 4-5hr trips and i don't even think about it. the biggest thing for me has been the ICM going out more frequently than i think it should. i carry a spare now....

 

[Vbb199]

if memory serves me right, you can bend the tab on the TPS to also adjust the idle voltage. i think a smooth voltage sweep is probably more important than resting at 0.5v. the gm manuals have a range of allowable voltage that may go to 0.7v, i don't remember.

i second the reliability of TBI. i regularly drive the suburban on 4-5hr trips and i don't even think about it. the biggest thing for me has been the ICM going out more frequently than i think it should. i carry a spare now....

I was under the impression .5-1v was ok at idle/closed, maybe not?

Vince and I were texting, but I’ll
post here so everyone can see my thought process. I agree that the resting TPS value is too high, and I agree with the .5V spec. My only objection is that your Joe Blow TPS from O’Reilly, even a decent one, doesn’t sit at that voltage. Maybe a Delco would, and you can add that to the list of OEM replacement parts that you shouldn’t skimp on. The best I’ve ever been able to get out of a aftermarket sensor is .59V after hogging out the holes, twisting it in the correct direction, and bolting it down. I’d try it. It almost sounds like an intermittently failing coil but not enough that I’d recommend a new one.

As far as the TBI goes as a system, in my experience, it can take a ridiculously long time to diagnose issues. My most effective recourse besides working with a rats nest of diagnostic equipment has been to power through the issue till it breaks completely. Once you work the bugs out, though, it’s great. I’ve been driving the bejeezus out of my Jimmy lately. It’s honestly my best vehicle right now. I could hop in it and drive to Commiefornia and back no problem. Of course, they’d probably stop me at Needles and not let me enter because it’s not even federal emissions compliant. Oh, well. It’s not like I want to go there anyway.

The coil was replaced with an aftermarket coil and ignition box actually fairly recently since the oem coil started fading on me badly.