Rough low acceleration

[Patterson]

I can’t figure mine out. It’s a 1987 r10 350 tbi Runs great but low acceleration is rough. That’s what kicked me off the smog test. I did the iac,engine temperature control, knock sensor,map sensor,02 sensor, set my timing, rebuilt my tbi all new gaskets new injectors , rotor, I sprayed and can’t find any air leaks. I think I may try a new distributor next

 

[Chevyguy]

I can’t figure mine out. It’s a 1987 r10 350 tbi Runs great but low acceleration is rough. That’s what kicked me off the smog test. I did the iac,engine temperature control, knock sensor,map sensor,02 sensor, set my timing, rebuilt my tbi all new gaskets new injectors , rotor, I sprayed and can’t find any air leaks. I think I may try a new distributor next

Check your Throttle Position Sensor.

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[AuroraGirl]

never discount the possibility of your timing to still be off because 1) your timing mark may not be 100% accurate anymore if your engine is high mileage or just oriiginal dampner, 2) we make mistakes. if you can advance your distributor slightly and it helps, i would look at if your computer is commanding knock retard for any reason and if your timing mark is proper

 

[Patterson]

I did replace the throttle position sensor it seems everything I do makes it better for a min then goes bad. Just to recap it’s 87 r10 5.7 I never drive it a lot it’s got 89k original miles. It’s just been running bad lately. Timing is at 0. Anything I replace is not a loss to me yet. So this week I’ve rebuilt the tbi ,new injectors, new fuel filter, rotor, o2 sensor, map sensor,Engine temp sensor, Iac sensor, egr,knock, thermostat, alternator was draining my battery changed that, pcv and hose. I Did the ignition module but then I went ahead and bought a whole new distributor today but have to install tomorrow 11-02-2020. So if that doesn’t work I’m dropping the fuel tanks and changing the senders and pumps. If that doesn’t do it the truck is getting dumped lol

 

[Nonstop]

Did you replace those parts for the hell of it, or was it done because of the smog issue? One thing that sticks out to me is the EGR. There are some “universal” ones that seem to be crap! It will give you poor part throttle response and it will stumble. Easy check for it - disconnect and plug the vacuum hose, then take it for a quick drive. If it runs better, well...

 

[Patterson]

I replaced them because I’ve had the truck for almost 20 years I’ve never had to put much maintenance into it. I’m just going through and upgrading everything while I’m trouble shooting. It’s just a beater I’ve used for hauling stuff Over the years really. But yes the low acceleration (2500 rpm approx) kicks me off the smog check because it’s not steady. 89k miles should tell you how much I drive this thing. I’m sure the tanks are next for me the senders and fuel pumps gotta be old and clogged