What (mechanically) could make a vehicle run rich? I have a 90 Chevy S-10 I am getting terrible gas milage, I can't start it after it's warm b/c it floods itself with fuel. I took apart the fuel injectors and they are dumping way too much fuel on the butterfly valve when the throttle cable is pulled. So what could cause a vehicle to inject too much fuel? I'm thinking maybe a vac hose that is sucking too much ... other ideas?? TIA



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Oct:55/57mmTB??

bad o2 sensor= bad gas milage/running rich etc..
if the o2 sensor goes bad your car will resort to default fuel maps which are usually super rich to prevent problems

What type of injection? TBI? TPI? ???

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That happened in my old 90 Skylark, turns out I fried the fuel injection chip in the computer, (EPROM?). bring it somewhere to get it (computer) read.

Ok, educate me here, what is TBI/TPI fuel injection? It's a 90, so it has the old carborater looking fuel injection system with the injector sitting in the center of the carb housing. And, thanks ^^^^ for the O2 sensor idea. I'll check that out.



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Oct:55/57mmTB??

its not carburated if its got injectors
carbs have bowls that hold the fuel and its pulled out by gravity etc..

I realize it is not carborated - what I am saying is that some of the first fuel injection systems that came out (late 80's/early 90's) borrowed the look and housing components of the old carborated systems - probably to save money on the manufactures part. I am not sure what they were called, but that is the type of fuel injection system I have in my truck - very different from the modern day fuel injection systems.



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Oct:55/57mmTB??

just an FYI, Fuel Injection has been around a lot longer than the late 80's, think OLD Corvette, like, the first ones that came out... they were fuel injected.

adam

>I realize it is not carborated - what I am saying is that
>some of the first fuel injection systems that came out (late
>80's/early 90's) borrowed the look and housing components of
>the old carborated systems - probably to save money on the
>manufactures part. I am not sure what they were called, but
>that is the type of fuel injection system I have in my truck
>- very different from the modern day fuel injection systems.

Yup :) The first fuel injection systems generally used were called throttle body injection (or single point injection). It basically had one injector right at the throttle body. It was easy and cheap to adapt this setup to cars that had carbuerators since all you needed to do was stick a throttle body with an injector where the carb used to be on top of the intake manifold. It just bolted on.

It was an effective setup for the time, better than carbs, and gave manufacturers a good stopgap while they developed better systems for the future.

See this webpage link below for more info. The second page in the article has most of the comparison info for carbs and fuel injection, but the whole article contains useful information.

http://www.howstuffworks.com/fuel-injection.htm

When you pull the throttle and its just stitting there, you're going to activate the accelleration pump. It's supposed to squirt a good amount of juice when you do this. How many injectors do you have? Run the engine with the TB open so you can see down into the venturi. When it's running, make sure that the injectors are spraying the same amount. Also make sure that that the injector isn't dripping from the nozzle. Try revving it to and holding it at a higher rpm. If an injector is dripping then replace it. If one is spraying inordinately more than the other then replace it. I'm sure there are probably other reasons why you would need to replace them but those are the reasons I know of. When you're running this kind of test with an open carb/tb don't put your face directly over top of it. Backfires can hurt so be careful.


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Thanks Metal Jim, what your describing is exactly what I was doing last night. I didn't think to really notice whether or not they were spraying evenly or whether one was dripping or not. I'll have to get back in there tomorrow and see exactly what's it's doing. As old as it is it's starting to sound to me like maybe I need to replace the injectors. ... and thanks to VX100 for explaining those fuel injections system much better than I did. Good info.



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Oct:55/57mmTB??