1987 chevy suburban acceleration problems

[everythingshard]

Sorry for this long long post but ive been through 100+ pages trying to help me.

I bought this 1987 Chevy suburban R10 RWD TBI (even though it has a logo thing on the truck that says "fuel injection" a year ago. for a little backstory, this truck sat under a awning on a property from 1994 to 2016 when i bought it. before i even turned it over to test drive it i did a change on all the fluids in the truck and allowed time to sit in the engine. it turned right over after that long! so i bought it.

i took it home and realized i was driving with a locked caliper and almost caught the tire area on fire, i replaced EVERYTHING involved with the brakes. the next thing i did was cut the catalytic converter off because of its age and it was full of crap and clogged. i installed a cherry bomb where the CAT was and just went straight piped out the back . it increased the power to the truck immensely. it ran amazing for a few days but then i noticed a loss of power when i would press the gas upon accelerating it would seem to take a lot of pressure on the pedal to accelerate. now its been three weeks and the acceleration is ghastly, when i'm already at speed, if i try to accelerate(even slowly) it seems to actually slow the truck down until i press it almost to the floor and it kicks into a higher rpm and takes off but sounds like its gonna hurt the truck(it acts like i'm pulling a huge trailer with another suburban on it lol) and if i let off the pedal at that point it goes back to losing power.

I have replaced : cap, rotor, calipers, brake booster, master cylinder, wires, plugs, air filter, pcv valve, belts, battery and maybe a few odds and ends.

keep in mind i have learned everything i now about mechanics from having to teach myself how to replace crap on this truck so keep that in mind.

Thanks for anything that helps

 

[1987 GMC Jimmy]

Have you gotten any SES lights since you started having problems? You can jump the two top right hand pins on the ALDL connector to pull the codes if so. You should get three Code 12s, and then it'll flash your stored trouble codes in groups of three. It stores up to three codes, and then it'll flash the three 12s again. The light should self-test when you first turn the key. If not, check the two fuses and make sure the bulb's not burnt. That's the place I'd start with this.

 

[everythingshard]

no codes

I have a service engine light that works. it isnt throwing any codes or showing the light. i know it works cause when i turn the ignition on it shows up with all the other dash lights. i was told at many auto shops that my year of vehicle didnt store codes(which seemed very unlikely to me)

 

[1987 GMC Jimmy]

Yeah, those shops didn't have a clue what they were talking about. No worries, though. This may completely bypass sensor and ECM concerns. You've done most of your replacements in the ignition department, but I'd like to know where your base timing is at. If you don't have a timing light, it's a critical tool to own. Your truck should be happy around 8-10* BTDC. If it's some degrees lower, bumping it up will help, but don't let it ping, and if it does while you're driving down the highway, dial it back a tad. That's what I'd check first. I don't know if you have an Autozone or an O'Reilly's near you, but they'll let you borrow tools. I would replace the fuel filter and do a fuel pressure test to start off on the fuel system. You can borrow the whole tester from one of those places. I don't know if NAPA, Advanced, or Carquest do it, but I'd check that out if it works better for you. You should see thirteen pounds of pressure, and you'll probably have to tee it in on the frame rail where the filter is. If you see thirteen pounds, maybe the filter fixed it, and see if it does any better. If not, it's time to drop the tank and replace the pump. You can get they stuff much cheaper from RockAuto if the shipping works out since you're in a non-contiguous state. I'd start from there if it were me. I would also check for vacuum leaks, too, because those'll hurt you. The easiest way would be to spray an aerosol combustible (i.e. starter fluid) around the TBI base to see if the idle changes, thus indicating a need for a new base gasket, but you can really just visually inspect most everything else. The EGR valve would be worth inspecting for issues. You can take it off, clean the carbon off the pintle, and depress the plunger to see if it moves back and forth properly. You can also depress it, cap your finger over the port, and see if it holds. If it passes both of these tests, it's good. This gets you started on your fuel and air component, and you've done a good bit on the ignition one. Unless the issue is something more complex with say the distributor or fuel injectors for example, the solution should be aforementioned.

 

[Polyphemus287]

Piggy backing off of what 97 Jimmy said, I'd check the fuel pressure with gauge. It sounds like your not getting enough fuel to the injectors. If possible, and you may have to be creative here, I'd check the fuel pressure under load.