91 chevy 4.3 bad miss way to much fuel


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91 chevy 4.3 bad miss way to much fuel

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Auto Repair Home>> Automotive Repair>> Car Troubleshooting

jeff b
Novice

Nov 28, 2009, 11:21 PM

Post #1 of 4 (3555 views)

91 chevy 4.3 bad miss way to much fuel	Sign In

91 chevy 4.3 iv been trying to figure this out iv replaced the 02sensor engin coolent sensor iac sensor the truck miss real bad when at idle almost wont run the injectors are pouring way to much fuel in but if i unplug one of the two injectors it runs almost perfect also ive changed the plugs wires router and cap and rebuilt the throttle body with new o rings ang gaskets any help greatly app thanks jeff b

steve01832
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Nov 29, 2009, 2:13 AM

Post #2 of 4 (3547 views)

Re: 91 chevy 4.3 bad miss way to much fuel	Sign In

This vehicle relies on the MAP sensor to regulate fuel injector pulse. First, double check the vacuum lines and verify no leaks. You can also pump the MAP sensor up with a hand held vacuum pump to see if the engine smoothes out. Another common problem on these vehicles was the Throttle Position Sensor. They had a tendency to rust up and the lever would stick telling the computer that the throttle was open resulting in a richer mixture. This is where a scan tool is best used so you can read the datastream as you do these tests to pinpoint the problem area.

Steve

Sidom
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Sidom profile image

Nov 29, 2009, 10:08 AM

Post #3 of 4 (3528 views)

Re: 91 chevy 4.3 bad miss way to much fuel	Sign In

Steve has some good advise and makes a real good point about seeing a data stream to get pointed in the right direction.

Those also had a problem with the coolant temp sensor connectors. If there are any doubts change it.

Is the check engine light on? Was there any codes....

steve01832
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Nov 29, 2009, 3:27 PM

Post #4 of 4 (3518 views)

Re: 91 chevy 4.3 bad miss way to much fuel	Sign In

Another thought. If these tests check out ok let's put a backpressure guage in the O2 sensor bung. If the exhaust is restricted that will lower our crank vacuum resulting in a lack of air being forced passed the throttle plate. Will also result in an overly rich mixture.

Steve

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