eric 87
Full Access Member
- Joined
- Aug 3, 2021
- Posts
- 89
- Reaction score
- 26
- Location
- Kentucky
- First Name
- Eric
- Truck Year
- 1987
- Truck Model
- GMC Sierra Shortbed
- Engine Size
- 305 tbi
Okay as promised I said I would get back and tell the truth good or bad in the TBI to carb swap. Funny this is going to be a mixed conclusion. Not 100% worked out the problem as I have some that....frankly are new to me. Yep so this starts off sort of if keeping score 1 for the TBI team. I have this issue with the truck wanting to die when I am at idle in a parking lot of driveway. Sort of a coast and turning into a parking lot or my drive it will die especially if I barely give it gas. Sort of light throttle. Not only did I only do a fast idle adjustment and electric choke adjustment then this issue started. But the fast idle was about 2500 or more. Being that I have not fooled around with a carb in years I thought let a known Holley guy make the dial it in sort of fine tuning to the carb. HE even made a house call because his shop is so backed up he wouldn't be able to get to it for a week.
Well he did a little to the idle mixtures and the accelerator pump on the carb was a bit tight so he adjusted that. As well as the fast idle also. He checked the floats and they were good. But we had it running long enough to warm it up good so we could not see how the adjustments affected to cold start. It was idling nice and smooth sitting there in the garage. No worries.
Well the next day this dying started at stop signs once it was warmed up. Hmm so I did a half turn on the curb idle screw. But the more I drove it...it began again.
I knew better than to do this myself. There is a guy a block from my house that has classic chevy's in his shop. He is also busy as can be so it took a few days to get it in. Well he I hate to say I think made it worse. Oh it idled fine for a bit but began the stalling again. A few times dying again at stops. Wife was riding with me and didn't like this. Got to get this fixed. SO this edge for the TBI is a solid one up. However it is a bit NOT because this carb when I give it gas and it goes....MAN does it go. Even with the lowly 305 , th400 and 2.73 gears it will turn the tires with ease and get on down the road when I punch it hard. SO performance the TBI never reacted this good EVER. Steady but not giddy up.
THis other shop tightened down the accelerator pump to where it was pushing the arm down nearly fully all the time. The dying got worse. And I did a 110 mile round trip this week and as I Drove longer it got worse and nearly didn't get me home. I had to really pump the gas to keep it running even when slowly down but not coming to a stop. I had one foot slowing the truck with the other pumping the gas literally to keep it running. I thought maybe my sender wasn't working correctly and I was running out of fuel. NOPE I stopped and it was correct as the left tank only took 7 gallons. I got it hope in the nick of time. Now I am mad because I paid two fellas combined over 100$ to make a few carb adjustments and it was worse.
I have now gone back through all the Holley How to videos and a few others and adjusted each thing by the book. So now it runs. BUT it still stutters and dies at times at low idle while coasting and trying to turn most often is when it dies. I have the idle at about 800. I have the timing at initial 8 btdc. Floats were double checked and they are at the bottom of the sight holes.
My one thing is I have this Holley mighty mite electric pump that I think is pumping just over 4-4.5 and wonder if that is the issue. HOWEver it isn't when I am jumping on it. Which is when I would think it would not pump enough. Nope it is at low idle and no or very little throttle that it dies.
NOW if anyone saw what I think ended up being the problem with my TBI....obviously had I caught this tiny pin missing in the ign module 4 pin plug I would have saved a ton of money and time and replaced that one plug. I do still have all the parts for the TBI. NO I don't think I would go back to the stock one. I have taken most of the computer wires out of the truck and the computer as well. IF I went back to a TBI set up it would be aftermarket with just a couple sensors involved. BUT I will sell this truck before I Do this.
I do have one other thing that may be my workmanship. I noticed there is more pressure in my radiator. Not overheating but pressure. I also not that when I remove the cap it really wants to push it out. AND the anti freeze is foamy. Not oil and no water in my oil. BUT is it possible that air is being pumped into the water from the engine? And would that air possibly be vacuum and be why it doesn't want to idle correctly? Would it be my intake gasket possibly doing both these things?
With the prices of cars now being over priced I was thinking I could still put in a long block and use these new parts I have. Intake ignition and carb....oh wait not intake since it has the TBI bolt pattern. BUT I would still be about 20k total in the truck. However has anyone noticed the prices have held and in many cases dropped from the hot market on these square bodies? I am seeing many at 15-20 with new replaced drivelines.
But I feel like it could be a big parts gun I would be shooting when I think this is adjustments still causing the issues. However would engine issues (this is a stock 305 that probably has never been rebuilt) from 87. I am thinking it is getting long in the tooth.
However my wife and I are not ones to have patience with things we can figure out and or get corrected. Even with safety glasses on the other day I was changing fuel filter and got a eye full of gas. BAD words were flying from my mouth as if I were in the exorcist as I got out from under the truck.
Overall I am okay with the swap. Like the TBI it is what you can make of it. I only saw that little tiny copper pin out of the plug as I was taking the truck apart. I had back pinned that plug and tested the circuit and it was good. Well the back pin made contact with the wire. That was making it run bad and throw the code 42.
Well I still intend on finding the issue. Over all the swap is fine and nothing is leaking that I know of unless that gasket is somehow letting air get into my water system pumping it up with pressure. I did the anti freeze test and it isn't the issue for the foaming. The only other option it says is a mechanical problem. I do not know what though.
I will do a better shorter and detailed parts list as well as things to watch for once I have it squared away.
To all of you in this group/ forum. I do appreciate the help and patience.
Well he did a little to the idle mixtures and the accelerator pump on the carb was a bit tight so he adjusted that. As well as the fast idle also. He checked the floats and they were good. But we had it running long enough to warm it up good so we could not see how the adjustments affected to cold start. It was idling nice and smooth sitting there in the garage. No worries.
Well the next day this dying started at stop signs once it was warmed up. Hmm so I did a half turn on the curb idle screw. But the more I drove it...it began again.
I knew better than to do this myself. There is a guy a block from my house that has classic chevy's in his shop. He is also busy as can be so it took a few days to get it in. Well he I hate to say I think made it worse. Oh it idled fine for a bit but began the stalling again. A few times dying again at stops. Wife was riding with me and didn't like this. Got to get this fixed. SO this edge for the TBI is a solid one up. However it is a bit NOT because this carb when I give it gas and it goes....MAN does it go. Even with the lowly 305 , th400 and 2.73 gears it will turn the tires with ease and get on down the road when I punch it hard. SO performance the TBI never reacted this good EVER. Steady but not giddy up.
THis other shop tightened down the accelerator pump to where it was pushing the arm down nearly fully all the time. The dying got worse. And I did a 110 mile round trip this week and as I Drove longer it got worse and nearly didn't get me home. I had to really pump the gas to keep it running even when slowly down but not coming to a stop. I had one foot slowing the truck with the other pumping the gas literally to keep it running. I thought maybe my sender wasn't working correctly and I was running out of fuel. NOPE I stopped and it was correct as the left tank only took 7 gallons. I got it hope in the nick of time. Now I am mad because I paid two fellas combined over 100$ to make a few carb adjustments and it was worse.
I have now gone back through all the Holley How to videos and a few others and adjusted each thing by the book. So now it runs. BUT it still stutters and dies at times at low idle while coasting and trying to turn most often is when it dies. I have the idle at about 800. I have the timing at initial 8 btdc. Floats were double checked and they are at the bottom of the sight holes.
My one thing is I have this Holley mighty mite electric pump that I think is pumping just over 4-4.5 and wonder if that is the issue. HOWEver it isn't when I am jumping on it. Which is when I would think it would not pump enough. Nope it is at low idle and no or very little throttle that it dies.
NOW if anyone saw what I think ended up being the problem with my TBI....obviously had I caught this tiny pin missing in the ign module 4 pin plug I would have saved a ton of money and time and replaced that one plug. I do still have all the parts for the TBI. NO I don't think I would go back to the stock one. I have taken most of the computer wires out of the truck and the computer as well. IF I went back to a TBI set up it would be aftermarket with just a couple sensors involved. BUT I will sell this truck before I Do this.
I do have one other thing that may be my workmanship. I noticed there is more pressure in my radiator. Not overheating but pressure. I also not that when I remove the cap it really wants to push it out. AND the anti freeze is foamy. Not oil and no water in my oil. BUT is it possible that air is being pumped into the water from the engine? And would that air possibly be vacuum and be why it doesn't want to idle correctly? Would it be my intake gasket possibly doing both these things?
With the prices of cars now being over priced I was thinking I could still put in a long block and use these new parts I have. Intake ignition and carb....oh wait not intake since it has the TBI bolt pattern. BUT I would still be about 20k total in the truck. However has anyone noticed the prices have held and in many cases dropped from the hot market on these square bodies? I am seeing many at 15-20 with new replaced drivelines.
But I feel like it could be a big parts gun I would be shooting when I think this is adjustments still causing the issues. However would engine issues (this is a stock 305 that probably has never been rebuilt) from 87. I am thinking it is getting long in the tooth.
However my wife and I are not ones to have patience with things we can figure out and or get corrected. Even with safety glasses on the other day I was changing fuel filter and got a eye full of gas. BAD words were flying from my mouth as if I were in the exorcist as I got out from under the truck.
Overall I am okay with the swap. Like the TBI it is what you can make of it. I only saw that little tiny copper pin out of the plug as I was taking the truck apart. I had back pinned that plug and tested the circuit and it was good. Well the back pin made contact with the wire. That was making it run bad and throw the code 42.
Well I still intend on finding the issue. Over all the swap is fine and nothing is leaking that I know of unless that gasket is somehow letting air get into my water system pumping it up with pressure. I did the anti freeze test and it isn't the issue for the foaming. The only other option it says is a mechanical problem. I do not know what though.
I will do a better shorter and detailed parts list as well as things to watch for once I have it squared away.
To all of you in this group/ forum. I do appreciate the help and patience.
