Running lean/bogging

[bambam78]

Hey guys, wondering if anyone has any ideas on why my 91 350 refuses to run right

On cold mornings when you go to turn it on it'll immidietly die, but fire back up easily, but under any kind of load, up hill or towing a trailer, it'll bog and act like it's running out of throttle, to the point that with my 2000lb car trailer it's hard to keep 65mph


So far I've replaced
Fuel filter
Fuel pump (getting 12 psi at the filter)
Rebuilt throttle body as well as a new regulator
New o2 sensor
New ICM
New CTS
New ECM
New knock sensor
New injectors
All vacuum hoses are good
New egr

After breaking down and taking it to a mechanic with live data he verified that all sensors was working properly, but the engine is running super lean, and the computer was pulling more and more fuel

Something like 120 was stock and it's running at like 165ish trying to pull fuel? I've lost the paper

Anyone have any ideaa

 

[LILJOEPEELZ05]

MAP sensor. It controls the air and fuel mix. Mine was feeding too much fuel and caused a high idle.


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[bambam78]

Could a map sensor be bad without throwing a code? I hooked a multimeter to it and it was within parameters

 

[LILJOEPEELZ05]

Yes. I had no code or light. As long as it’s plugged in the simple computer thinks it’s all good


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[PlayingWithTBI]

I'm guessing you are running in closed loop? What's an ICM, do you mean Idle Air Control? If you don't have an exhaust leak near the o2 sensor, you may have a vacuum leak somewhere like intake manifold gaskets. Spray some carb cleaner all over with the engine running and see if it changes.

 

[Crookedaxle]

Hey guys, wondering if anyone has any ideas on why my 91 350 refuses to run right

On cold mornings when you go to turn it on it'll immidietly die, but fire back up easily, but under any kind of load, up hill or towing a trailer, it'll bog and act like it's running out of throttle, to the point that with my 2000lb car trailer it's hard to keep 65mph


So far I've replaced
Fuel filter
Fuel pump (getting 12 psi at the filter)
Rebuilt throttle body as well as a new regulator
New o2 sensor
New ICM
New CTS
New ECM
New knock sensor
New injectors
All vacuum hoses are good
New egr

After breaking down and taking it to a mechanic with live data he verified that all sensors was working properly, but the engine is running super lean, and the computer was pulling more and more fuel

Something like 120 was stock and it's running at like 165ish trying to pull fuel? I've lost the paper

Anyone have any ideaa

FWIW when it's below 10F or so mine surges and acts like it's running lean so I try to mix in some non-oxy premium with the ethanol gas that we're required to run in Minnesoder so I'm running about half and half. Mine is still driveable though without doing this. Same symptoms, but just not as bad it sounds like.

 

[bambam78]

I'm guessing you are running in closed loop? What's an ICM, do you mean Idle Air Control? If you don't have an exhaust leak near the o2 sensor, you may have a vacuum leak somewhere like intake manifold gaskets. Spray some carb cleaner all over with the engine running and see if it changes.

Ignition control module under the distributor cap

No exhaust leaks and I'm fairly certain it doesn't have any vacuum leaks, the egr is brand new, and all hoses hold vacuum, a vacuum guage holds a steady 19, and I haven't found any at the front or back of the intake

I guess for now I'll throw in a different map sensor and see if it changes anything

 

[woody80z28]

After breaking down and taking it to a mechanic with live data he verified that all sensors was working properly, but the engine is running super lean, and the computer was pulling more and more fuel

Something like 120 was stock and it's running at like 165ish trying to pull fuel? I've lost the paper

Anyone have any ideaa

I'm guessing you're referring to BLMs. 128 would be no change, and 165 would be adding a ton of fuel. If it's trying to add a ton of fuel via o2 feedback and still acts lean, you have a fuel delivery issue.

The other possibility is an inaccurate o2 flooding it out. But you should be able to tell at the tail pipe if it's lean or rich.