Need help
Thread Starter
7th Gear
Joined: Jun 2006
Posts: 7
Likes: 0
Need help
I have a '96 c.e. auto. The problems are that while its running it idles very low around 500 rpms and it uses gas twice as much as usual. I went form having about 18 mpg to now having 15 mpg driveing the same route.
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
on my '95, one of my O2 sensors crapped out, and my gas mileage went down to about 12mpg. My idle also dropped and stumbled due to the bad O2 sensor, which must have been sending a constant lean voltage condition to the ECM, which in turn constantly over richened one bank of cylinders.Did you check for error codes???
Thread Starter
7th Gear
Joined: Jun 2006
Posts: 7
Likes: 0
i did have it checked for codes, he said that he had gotten hits on the o2 sensers, and the m.a.f senser. i don't think its the o2's because all of them were replaced 2 years ago at the same dealer. he had said something about cleaning the m.a.f senser does anyone know how to do that or at least what i need to that. I was also reading another tread about a '95 that was having vacum problems and the symptoms could that be a cause as well. any information i can get will be extremly helpfull
Team Owner
Joined: Jun 2005
Posts: 46,295
Likes: 2,596
From: Northern, VA
St. Jude Donor '15
"In honor of jpee"
i did have it checked for codes, he said that he had gotten hits on the o2 sensers, and the m.a.f senser. i don't think its the o2's because all of them were replaced 2 years ago at the same dealer. he had said something about cleaning the m.a.f senser does anyone know how to do that or at least what i need to that. I was also reading another tread about a '95 that was having vacum problems and the symptoms could that be a cause as well. any information i can get will be extremly helpfull
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
On a very long shot, check the wiring off the O2 sensors. See if there are any wires that are broken, burnt by pipe, connector damaged or contacts need to be cleaned due to corrosion. If I remember correctly, the 96 has 4 O2 sensors. Check them all 
Racer
Joined: Dec 2006
Posts: 367
Likes: 0
From: Beaver Dam Kentucky
I had a simular problem about a year ago. The car (96 with 120,000 miles) was idling bad and was smoking while it was running. I had a shop (because I was new to corvettes) to change the plugs, optispark, and wires. When they were done I ask them if it took care of the problem. They said what problem. I replied, the miss and smoking. They said that you told us to change these items. You didn't ask what was wrong with your car. They checked the codes and said it was a bad o2 sensor, changed it and the problem solved....and about $800.00 for guessing.
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Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
Just because the sensors were recently replaced doesn't mean they won't go bad on you. I just tuned a guys LS1 that was installed in a H1 Hummer about 4 weeks ago. Prior to that they had just installed the engine with no name brand o2 sensors. It came back about two weeks after I tuned it with a strange problem of lugging when at light load throttle. I checked it with my trusty TECH2 and found that the right o2 sensor was going nuts at part throttle and telling the PCM that it was extremely lean. The PCM in turn cranked up the fuel to a point that it pegged the long term fuel trims. If your dealer or shop used dollar store no name brand generic sensors I would definitely start checking them.
I doubt that the MAF is the culprit, the reason I say this is because even if the sensor was slightly fouled, the sensor's sensing element is usually desensitized, when this happens not all of the incoming air is measured, so in turn the o2 sensors reports a sligtly lean condition and then the PCM will correct for that. The big problem comes when the o2 sensors report a lean condition that doesn't exist, that is when your fuel mileage goes into the toilet.
I doubt that the MAF is the culprit, the reason I say this is because even if the sensor was slightly fouled, the sensor's sensing element is usually desensitized, when this happens not all of the incoming air is measured, so in turn the o2 sensors reports a sligtly lean condition and then the PCM will correct for that. The big problem comes when the o2 sensors report a lean condition that doesn't exist, that is when your fuel mileage goes into the toilet.
