The thought came to me when I found the throttle shaft seized on my 04 Ion. I have it out soaking in WD40. It's a cable actuated mechanical TB. Wondered if it would it start and run like that? (no I wont' try it) Would the engine overspeed like a runaway diesel since it's the same as a fully open throttle when you floor it? Would the disconnected TPS prevent it from overrevving by going into limp mode. I assume a rev limiter will cut the ignition at a certain speed, no? And what if the TB was removed and set aside but still plugged in to the TPS?
Theoretically, will an engine run with the throttle body removed?
- Thread starter atikovi
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There would be a vacuum leak and it would stall, unless you keep your foot on the gas, and then it will smell like burning
Not all engines have throttle bodies and many don't have conventional throttle bodies. If a vehicle has a throttle body it will very likely not run well or not at all without that component.
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What would keeping your foot on the gas do when the throttle body is off the engine? It's already like flooring it.
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It would default to base table for fuelling if it would fuel at all with the TPS disconnected (it may default to fuel shutoff). Since it would have no air restriction it wouldn't run, it would be way too lean but might fire for a second and rev super high before dying.
A Throttle Body is different from a Carburator ........ when you put pedal to the floor on a Carb engine its giving it all gas . Pedal to the floor on a Throttle Body engine is giving it all Air .
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Well technically foot the floor (assuming the choke is open) on a carb is giving it the ability to draw in as much fuel and air as possible, but the amount of fuel drawn is based on the venturi effect, you aren't just dumping a ton of gas into the engine without restriction (ignoring the accelerator pump dumping some fixed volume of fuel in a single shot), it's metered and tied to the volume of air being ingested.
It did on my neon!
The throttle bodies on those are, for whatever reason, connected to a flexible plastic air tube that then goes to the intake. My hose clamp slipped off and she took off on me. Luckily it was a stick shift so I just declutched.
In the old days if you found a junkyard motor without a carb, and wanted to prove it ran, you'd stuff a rag in the intake and dribble some gas on it.
The throttle bodies on those are, for whatever reason, connected to a flexible plastic air tube that then goes to the intake. My hose clamp slipped off and she took off on me. Luckily it was a stick shift so I just declutched.
In the old days if you found a junkyard motor without a carb, and wanted to prove it ran, you'd stuff a rag in the intake and dribble some gas on it.
And possibly wide open! I remember a story about a guy that removed the intake manifold from a car, then hit the key to turn it over. Ran out of control.
When I worked at a Pontiac Buick dealership back in '67, the owners told a guy with a car that was known to not run, that if he could drive it onto the lot they would take it in trade.
The guy towed the car up to the lot with a farm tractor, and then with a rag stuffed in the intake and gasoline dripping on the rag started it up and drove it onto the lot. They were as good as their word and took it in trade.
$25?
Probably slightly more as I believe that was before the 2007 or 2008 bailout.
What tells the computer to give it gas?
I think they had agreed on the trade in value in advance. $250 or $500 maybe. Better than towing it into the bush which is what usually happened to non-running cars in that area.
The ecu looks at the exhaust O2 sensors and adjusts the fuel for a proper air to fuel ratio.
Wide open air intake, engine cylinders position saying the crank is turning, and at the proper time it will fire the sparkplugs, O2 sensors say lean, air fuel computer map combined with engine temperature sensor(s) and or coolant temp sensor(s) and it will supply fuel when it should unless there is some code written in the computer for sensing something is so wrong that it should not run.
So, it depends on what the programing of the ecu looks at and what it is seeing. And that can vary with different makes and maybe even different engines and or models of even any brand.
Computers can't think (at least not yet). They execute programs that are prewritten using data put into them from sensors. And some companies spend more on programing than others, so there can be different results when unusual input is put into the ecu depending on the programing.
In 1967? Kinda doubt that. Good used cars sold for $250 or $500 back then.
I'm trying to picture this. Wouldn't there be a huge risk the rag gets sucked into one of the runners of the manifold?
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That's only in closed loop, which isn't happening on startup.
The oxygen sensor input will be ignored, because it won't go into closed loop with no TPS signal.
This hinges on whether the ECM will still fire the injectors with no throttle position sensor. If it will, a couple things are possible:
1. If the vehicle is MAF, it will see 0 airflow and either:
- assume the MAF is bad and go into base table, so just idle levels of fuelling and immediately lean-stall
- or, assume MAF is correct and there is no airflow and lean stall.
2. If the vehicle is MAP, it will see no vacuum and either:
- assume both it and the TPS are invalid and go to base table fuelling, lean stalling
- ignore the lack of TPS and go to 100% load fuelling, going off the rev limiter and possibly blowing up.
Yup, some use redundant POT's to confirm sanity of inputs, some don't. I had a TPS go bad on my Mustang, which increased fuelling and it started idling at like 2,500RPM, lol.
I wasn't using my brain one day and I started the snowmobile with the throttle slide out... I was showing my kids how the carb worked and how the thumb throttle moved the slide, then how the primer squirts extra gas in behind the throttle slide. And then I pulled it over slowly to show how the engine sucks in the air and fuel, and it popped once and bwooooaaaaahhhh! Fortunately it died in about a second, and I had the track off the floor...
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