Vince's TBI woes, progressive revelations, and tbi mods.
- Thread starter Vbb199
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
Big Chip
Full Access Member
- Joined
- Oct 19, 2017
- Posts
- 4,656
- Reaction score
- 6,734
- Location
- Michigan
- First Name
- Kevin
- Truck Year
- 1979
- Truck Model
- C35
- Engine Size
- 454
My first thought was to take that junk right up to 88mph, go back in time and take care of it a little better, take it back up to 88mph, come back to the future and just enjoy your sweet trouble-free rig.
Maybe next time.
gmbellew
Full Access Member
- Joined
- May 27, 2018
- Posts
- 1,214
- Reaction score
- 1,283
- Location
- Kansas city
- First Name
- glen
- Truck Year
- 1990
- Truck Model
- suburban 1500
- Engine Size
- 350
i checked my TPS today. at idle it is .66v and WOT using the skinny pedal is 1.45v (edit - 4.45v). i didn't go under the hood and check with the linkage.
WOT voltage is good. idle voltage is a little higher than I'd like, but not crazy. maybe if it ever warms up, i will drop a new one in. although the truck runs well, and i always hate to mess with something that is working...
WOT voltage is good. idle voltage is a little higher than I'd like, but not crazy. maybe if it ever warms up, i will drop a new one in. although the truck runs well, and i always hate to mess with something that is working...
Last edited:
gmbellew
Full Access Member
- Joined
- May 27, 2018
- Posts
- 1,214
- Reaction score
- 1,283
- Location
- Kansas city
- First Name
- glen
- Truck Year
- 1990
- Truck Model
- suburban 1500
- Engine Size
- 350
sorry, typo. it was 4.45....
Chevyguy
Full Access Member
- Joined
- Sep 10, 2012
- Posts
- 186
- Reaction score
- 60
- Location
- Eugene,OR
- First Name
- Clayton
- Truck Year
- 1987
- Truck Model
- V20
- Engine Size
- 5.7 Litre
You're good to go at WOT then. I still think your TPS may need replacement due to the higher than specifications voltage at closed throttle.
Clayton
Sent from my SM-A705U using Tapatalk
1987 GMC Jimmy
Automobile Hoarder
- Joined
- Jan 23, 2016
- Posts
- 5,848
- Reaction score
- 2,389
- Location
- Mississippi
- First Name
- Jesse
- Truck Year
- 1987
- Truck Model
- V1500 Jimmy
- Engine Size
- 350
A few thoughts...
One, that resting TPS value is too high, and I don’t think it can be remedied with the current sensor. You can always try, but I think the cheapo ones rest at about at .66V, and I adjusted that down to .59V by boring the holes and slightly clocking the sensor. I wouldn’t worry too much about the high side because the carpet being an obstruction to the gas pedal is a very real thing. You can always get it close to the upper end when you’re working the throttle manually. Also, is everything okay with the grounds? I’ve seen a missing engine to firewall strap throw a TPS code.
Two, is the idle screw still sealed on your TBI unit? Not trying to beat a dead horse, but the idle’s a bit too high even when it’s warmed up. The IACV counts seem a tad high, but I wouldn’t run to replace the thing just yet. Making sure the sensor pintle is clean, the air passages underneath are clean, and doing a relearn could help in that situation in conjunction with getting that TPS voltage down. It looks like the lowest you ever got was 51 counts. That’s not terrible, but I think I sit at 40 steps in a warm, parked idle at roughly 800 RPM. In drive, warm I sit at 0 with an engine speed of about 600 RPM. 20-50 is the ballpark range you want it to settle to in park, but it ultimately depends on the vehicle.
Three, what’s your vacuum, like 22” you said? That’s really good, and the MAP sensor confirms. Just out of curiosity, what’s your approximate altitude there?
Four, I wouldn’t pay a lot of mind to the TPS calculations. The BLM/INT look fine, and I don’t see an injector duty cycle calculation, but that’s the one that gives me totally ridiculous feedback.
I think that’s all I have.
One, that resting TPS value is too high, and I don’t think it can be remedied with the current sensor. You can always try, but I think the cheapo ones rest at about at .66V, and I adjusted that down to .59V by boring the holes and slightly clocking the sensor. I wouldn’t worry too much about the high side because the carpet being an obstruction to the gas pedal is a very real thing. You can always get it close to the upper end when you’re working the throttle manually. Also, is everything okay with the grounds? I’ve seen a missing engine to firewall strap throw a TPS code.
Two, is the idle screw still sealed on your TBI unit? Not trying to beat a dead horse, but the idle’s a bit too high even when it’s warmed up. The IACV counts seem a tad high, but I wouldn’t run to replace the thing just yet. Making sure the sensor pintle is clean, the air passages underneath are clean, and doing a relearn could help in that situation in conjunction with getting that TPS voltage down. It looks like the lowest you ever got was 51 counts. That’s not terrible, but I think I sit at 40 steps in a warm, parked idle at roughly 800 RPM. In drive, warm I sit at 0 with an engine speed of about 600 RPM. 20-50 is the ballpark range you want it to settle to in park, but it ultimately depends on the vehicle.
Three, what’s your vacuum, like 22” you said? That’s really good, and the MAP sensor confirms. Just out of curiosity, what’s your approximate altitude there?
Four, I wouldn’t pay a lot of mind to the TPS calculations. The BLM/INT look fine, and I don’t see an injector duty cycle calculation, but that’s the one that gives me totally ridiculous feedback.
I think that’s all I have.
Vbb199
B-rate Hillbilly Customs
- Joined
- Jan 12, 2018
- Posts
- 9,039
- Reaction score
- 15,332
- Location
- Salisbury NC
- First Name
- Vince
- Truck Year
- 89, 79
- Truck Model
- 89 Suburban R1500, 79 C10
- Engine Size
- 350, 502
1. I have bored the holes out on the replacement unit, i just had never adjusted it. It wasnt the bottom dollar unit. i think.... standard ignition was the name? Theyre american made i believe. I DID notice since i pulled the trans out, a harness strap is broken. But as you know, there are many straps on the harness, but i probably need that 1 working .
2. Yes, ive reset the idle thru the proper proceedure several times. I have a leak somewhere or something causing that high idle. IAC has been replaced maybe.. 10 months ago now? Idle was high even when i first got the shitbox from its tree-side grave.
3. Yes, the motor makes 22 in/hg at the front of the throttle body, but my map kPa readings are low? 26-28 kPa is like an avg. Of 8 in/hg?? I dont follow where you are going. As far as approx altitude, the internet says we are 791' above. I kmow they are not directly related, but i personally do not know in what capacity they are related, if that makes sense.
4. Those calculations are indeed retarded. I contacted the app developer, he said that was a defunct .adx file (used for communication with ecm), he said at my current voltage at idle, its more like a 18% load. He sent another .adx, but i didnt install it.
All of this is good data, for sure. Im just as suspicious of grounds, and as i said, im gonna look into that broken ground, AND the ground running from motor to the cab. If i remember correctly, that strap is.... on the passenger side? Of the firewall? I will look into engine straps.... still in transmission mode at the moment. I just got the pos put back together last night.
Last edited:
seniorbear69
Member
- Joined
- Oct 1, 2020
- Posts
- 49
- Reaction score
- 19
- Location
- rayleigh essex uk
- First Name
- steve
- Truck Year
- 1984
- Truck Model
- c20
- Engine Size
- 350
who ould you recomend to supply a moded chip?
Urbanburban22
Member
- Joined
- Apr 22, 2022
- Posts
- 34
- Reaction score
- 42
- Location
- Colorado
- First Name
- David
- Truck Year
- 1991
- Truck Model
- Suburban SLE V1500
- Engine Size
- 5.7 TBI
you can get chips? What exactly is PROM? How/where could I find the right chip for a 91 tbi?
Vbb199
B-rate Hillbilly Customs
- Joined
- Jan 12, 2018
- Posts
- 9,039
- Reaction score
- 15,332
- Location
- Salisbury NC
- First Name
- Vince
- Truck Year
- 89, 79
- Truck Model
- 89 Suburban R1500, 79 C10
- Engine Size
- 350, 502
I had a guy online burn one for me, but ive since found another guy who has moates and PROM burning capability.
PROM contains the programmable parameters for the PCM
AuroraGirl
Full Access Member
- Joined
- Sep 8, 2019
- Posts
- 9,693
- Reaction score
- 6,869
- Location
- Northern Wisconsin
- First Name
- Taylor
- Truck Year
- 1978, 1980
- Truck Model
- K10, K25
- Engine Size
- 400(?), 350
have a stock setup? Want a gm issued PROM? give me your vin and I can tell you what chips to buy
AuroraGirl
Full Access Member
- Joined
- Sep 8, 2019
- Posts
- 9,693
- Reaction score
- 6,869
- Location
- Northern Wisconsin
- First Name
- Taylor
- Truck Year
- 1978, 1980
- Truck Model
- K10, K25
- Engine Size
- 400(?), 350
@Urbanburban22 did you resolve this then
Vbb199
B-rate Hillbilly Customs
- Joined
- Jan 12, 2018
- Posts
- 9,039
- Reaction score
- 15,332
- Location
- Salisbury NC
- First Name
- Vince
- Truck Year
- 89, 79
- Truck Model
- 89 Suburban R1500, 79 C10
- Engine Size
- 350, 502
Visiting my threads for my scrap heap i see
