Deciphering Live Data.

[Caman96]

Anyone have any ideas to why my truck is still sluggish?

Is it sluggish compared to what it was once or sluggish to what you think it should be?

 

[Schurkey]

1988 TBI

Truck is extremely sluggish and down on power, seems like timing is having trouble advancing and now at low acceleration it surges a bit, low as in really really low.

Im starting to wonder if it some sort of injector issue. The truck had developed a pretty good misfire on start and pretty consistent under light load. I just checked and recently my passenger exhaust (true dual) was full of carbon but the driver was fine. I just checked and at idle the truck is putting out some hefty blue smoke out the passenger side but the driver is next to nothing,

Anyone have any ideas to why my truck is still sluggish? Everything is replaced but it still is sluggish and everything looks ok on the live data

I just skimmed this thread. Four Five pages of posts on my computer.

I haven't seen any confirmation that you've ever tested fuel pressure at prime, at idle, or under load. How old is the fuel filter?

You've noticed carbon and blue smoke from the right bank, none from the left bank. Have you performed a compression test? Leakdown test? Cylinder-balance test? Oil-burning will likely destroy the catalyst; does this truck even have a catalyst? (or two.)

You said you replaced the distributor cap and ignition module. How about all the rest of the "tune-up" parts 'n' procedures? You claim to have replaced "everything", but no mention of spark plugs, plug wires, distributor rotor, PCV, EGR, EVAP, heated-air intake, catalyst(s), O2 sensor, verifying base timing, electronic timing advance, air filter, and so forth. Do you buy Top Tier fuel? Do you ever dump Techron Complete Fuel System Cleaner or a similar injector-cleaning product into the gas tank? Are you SURE you got the CORRECT knock sensor?

 

[Nick88]

how can that be possible based on what we have pointed out? do what i said above then post the new warm idle and maybe a warm light cruise at around 20 mph constant flat ground so we can go from there

Everything is the exact same. The only difference was cleaning out the carbon and reading data so I dont see how resetting the computer would help, probably revert to the same way, as it has in the past when I reset battery.

 

[Nick88]

I just skimmed this thread. Four Five pages of posts on my computer.

I haven't seen any confirmation that you've ever tested fuel pressure at prime, at idle, or under load. How old is the fuel filter?

You've noticed carbon and blue smoke from the right bank, none from the left bank. Have you performed a compression test? Leakdown test? Cylinder-balance test? Oil-burning will likely destroy the catalyst; does this truck even have a catalyst? (or two.)

You said you replaced the distributor cap and ignition module. How about all the rest of the "tune-up" parts 'n' procedures? You claim to have replaced "everything", but no mention of spark plugs, plug wires, distributor rotor, PCV, EGR, EVAP, heated-air intake, catalyst(s), O2 sensor, verifying base timing, electronic timing advance, air filter, and so forth. Do you buy Top Tier fuel? Do you ever dump Techron Complete Fuel System Cleaner or a similar injector-cleaning product into the gas tank? Are you SURE you got the CORRECT knock sensor?

Fuel Pressure is 13 Psi constant even at load, fuel filter is brand new and strainer and pump and regulator and all lines.

I think the smoke was just some carbon on the valves not seating them fully, all smoke is completely gone now at flushing motor with steam clean. No catalyst.

Spark plugs are new, wires are new, knlck sensor is new, distributor is new, rotor is new, cap is new, pcv was new then replaced with cleaned factory, egr is new, the heated intake thermac didnt work right so i strung it open, no catalyst, o2 new, base timing is 0, advance is good at idle in park, air filter is brand new. I only use name brand gas, ran plenty of injector cleaner for a while in a ethanol treatment I used for a while, nice cone on injectors too. Yes knock sensor is for 350 with auto. Ac Delco. Knocks are somine resolved, they go up to like 3-5 on start then seem to stay there sometimes gain a couple while driving around.

I have replaced everything completely, Ignition and Fuel which is why Im so stumped. the only thing left is the injectors and connectors, which the injectors have a good cone so I doubt, but the connectors seem loose. Either that or something is causing timing to retard somehow.

 

[Nick88]

Is it sluggish compared to what it was once or sluggish to what you think it should be?

To what it once, for a while it was really peppy. Truck would move really good, to the point id be tailgating by accident because it eould just go, now getting to 40 is a struggle.

 

[AuroraGirl]

Everything is the exact same. The only difference was cleaning out the carbon and reading data so I dont see how resetting the computer would help, probably revert to the same way, as it has in the past when I reset battery.

You WANT it to revert as its designed to do when the battery is reset.

fuel filter is brand new and strainer and pump and regulator and all lines

knlck sensor is new, distributor is new, rotor is new, cap is new, pcv was new then replaced with cleaned factory, egr is new, the heated intake thermac didnt work right so i strung it open, no catalyst, o2 new, base timing is 0, advance is good at idle in park, air filter is brand new. I only use name brand gas, ran plenty of injector cleaner for a while in a ethanol treatment I used for a while, nice cone on injectors too.

I have replaced everything completely, Ignition and Fuel which is why Im so stumped. the only thing left is the injectors and connectors, which the injectors have a good cone so I doubt, but the connectors seem loose. Either that or something is causing timing to retard somehow.

nick, im not going to address every single thing I bolded, increased in size, but you are not presenting us a very credible story since you cannot have COMPLETELY REPLACED EVERYTHING while RIGGING A DRIVEABILITY DEVICE INTO A FAILURE MODE PERMANENTLY and you cannot assume the only thing left is parts you havent hit with your canon yet.

Have you replaced all these parts because they were worn or because you were replacing parts?

Go back to your box of parts you should have kept because they were still working, and ask yourself "why did I replace this."

If you just did because why not , then put it the hell back on your truck and keep the parts canon one for a spare.

You have not provided brands or part numbers like, at all, except "ac delco" knock sensor. You are aware AC delco has more than one knock sensor for a 350 auto trans? Part number, please. You also could have used something on the threads, or over/under torqued.

How did you go about setting base timing?


Im going to send you a video about 350 TBI engines about determining if the timer core magnet is weak wwithout removing the distributor by using a timing light which I assume you have. Also your timing mark could have slipped.. didnt see a balancer on your parts canon.

xc_hide_links_from_guests_guests_error_hide_media

I linked the time in the video so clicking it will bring you to the exact information I was referencing.

lastly, 1988 is the first year of the gmt 400. you could conceivably be looking at a computer issue, a prom calibration thats been overrided (I guarantee the 350 sbc auto in 1988 has at least 4 different possible PROM replacements that are tied to a TSB related to driveability, only being done if they showed the behavior.. its just howi t was on something so new and developing.

If you post your VIN and your PROM current 4 digit code I can check into what may be available stock to possibly be for this, as well as potential other interactions that may be relevant.
you should be able to see your PROM on your live data stream iirc

 

[Nick88]

You WANT it to revert as its designed to do when the battery is reset.


nick, im not going to address every single thing I bolded, increased in size, but you are not presenting us a very credible story since you cannot have COMPLETELY REPLACED EVERYTHING while RIGGING A DRIVEABILITY DEVICE INTO A FAILURE MODE PERMANENTLY and you cannot assume the only thing left is parts you havent hit with your canon yet.

Have you replaced all these parts because they were worn or because you were replacing parts?

Go back to your box of parts you should have kept because they were still working, and ask yourself "why did I replace this."

If you just did because why not , then put it the hell back on your truck and keep the parts canon one for a spare.

You have not provided brands or part numbers like, at all, except "ac delco" knock sensor. You are aware AC delco has more than one knock sensor for a 350 auto trans? Part number, please. You also could have used something on the threads, or over/under torqued.

How did you go about setting base timing?


Im going to send you a video about 350 TBI engines about determining if the timer core magnet is weak wwithout removing the distributor by using a timing light which I assume you have. Also your timing mark could have slipped.. didnt see a balancer on your parts canon.

xc_hide_links_from_guests_guests_error_hide_media

I linked the time in the video so clicking it will bring you to the exact information I was referencing.

lastly, 1988 is the first year of the gmt 400. you could conceivably be looking at a computer issue, a prom calibration thats been overrided (I guarantee the 350 sbc auto in 1988 has at least 4 different possible PROM replacements that are tied to a TSB related to driveability, only being done if they showed the behavior.. its just howi t was on something so new and developing.

If you post your VIN and your PROM current 4 digit code I can check into what may be available stock to possibly be for this, as well as potential other interactions that may be relevant.
you should be able to see your PROM on your live data stream iirc

No parts canon, truck was all the factory sensors when I bought it, everything was worn and I diagnosed before I replaced with multi meter, certain stuff (TPS and Map) are original but I tested them good multiple times which is why I never mentioned them or replaced them. Trying to find a thermac replacement that works is harder than just leaving it open, before it was stuck shut.

I kept all the spares because the truck runs on them but poorly, which is why it is all new.

Nothing on threads and it is spot on 14 lbs I gotta look for part number on the receipt

Disconnect tan black wire and set to 0.

I will watch that video thank you. I was also suspicious of balancer but sometimes it runs perfect so it wouldnt make any sense.

 

[PlayingWithTBI]

the heated intake thermac didnt work right so i strung it open,

What;s a "heated thermac"?

 

[Erik the Awful]

Thermal actuator - the flap in old style air cleaners that opened when the engine finally warmed up.

 

[PlayingWithTBI]

Thermal actuator - the flap in old style air cleaners that opened when the engine finally warmed up.

Thanks - so, we're running with heated air all the time and are wondering why we're getting KCs?