Rough idle and rough acceleration and low idle NEED HELP!

[FarmTrok]

Recently my 92 c1500 305 v8 has been acting up for a while actually. Every time i start it in the morning it sounds like there is a cam or something like a loop going on, the RPMs go up and down rather smooth. Its not like a rough fluctuation its rather a smooth one. After i tap the gas it will even out most of the time or act like its going to die.

Then when i put it in drive and go down the road it sounds and drives awful its like its breaking up really choppy. After i drive for a few minutes its like it switches to a new sensor or something its fine minus the low idle at a stop light or something, where sometimes here and there not often it will die. I got my intake gasket replaced by a shop along with a new distributor kit and boy it ran like new it rand great but the next day it went back to running like junk.

Heres a list of what I've replaced since it has started.

Thermostat and all new hoses

MAP

IAC

ECTS

ECTG

TPS

EGR

Air filter

Power steering pump

Alternator

Battery

Fuel pump

Fuel filter

Intake manifold gasket

Distributor and cap

Spark plugs and wires

 

[PlayingWithTBI]

Check you fuel pressure, GM says 9 - 13PSI but it's better to see 11 - 13. Shine a flashlight behind the injectors while idling and see if they're spraying evenly with no drips. Did you set your initial base timing? Did you calibrate your Throttle Body after changing all that stuff?

TBI tuning-website - Tuning the TBI.pdf

 

[Steve A]

Double check the EGR valve, make sure it's fully closing.

 

[FarmTrok]

Check you fuel pressure, GM says 9 - 13PSI but it's better to see 11 - 13. Shine a flashlight behind the injectors while idling and see if they're spraying evenly with no drips. Did you set your initial base timing? Did you calibrate your Throttle Body after changing all that stuff?

TBI tuning-website - Tuning the TBI.pdf

I just now saw this reply. Ill check the fuel pressure, but i couldn't imagine it being the fuel pump because it did the exact same thing with the old fuel pump. The injectors spray fine.

now the timing thing could be a culprit and kind of makes sense. The shop replaced it along with the intake gasket and that’s probably when they set the timing correctly. I did notice that the hold down bolt was not tightened all the way a couple days later and i could move the distributor cap back and forth. (I didn’t adjust it much cause i still wanted the truck to run) I just cant find the pulley that has the timing numbers on it to shine the light on.

how can i calibrate the throttle body? My throttle body doesn't have a idle screw, and i don't think i can tune it bc its a 92 with a obd 1.

 

[FarmTrok]

Double check the EGR valve, make sure it's fully closing.

how can i check that?

 

[PlayingWithTBI]

Ill check the fuel pressure, but i couldn't imagine it being the fuel pump because it did the exact same thing with the old fuel pump.

The pressure regulator on the back of the throttle body could be weak and not giving you enough pressure.

I just cant find the pulley that has the timing numbers on it to shine the light on.

The harmonic balance has a notch in it and the timing cover has a plate (with serrations for TDC, +2*, +4*, and +6* IIRC) sticking out above the harmonic balancer on the left side.

My throttle body doesn't have a idle screw, and i don't think i can tune it bc its a 92 with a obd 1.

The idle screw is behind the cap on the front left side of the throttle body. The "tuning" I'm talking about is the IAC and TPS.

BTW, you can definitely tune the OBD1 ECMs/PCMs with TunerPro RT, an ALDL cable, and an emulation adapter or a flash chip with an adapter socket. Here's a picture of TP on my 88 while data logging which would really help you find your issue if it's not fuel pressure, initial timing, and/or TB calibration.

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[PlayingWithTBI]

The link I posted above shows where your idle screw is and how to calibrate it.