Does No Check Engine Light Mean No Codes or Trouble - Poor M - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 11-05-2004, 10:15 AM   #1
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Default Does No Check Engine Light Mean No Codes or Trouble - Poor M

I haven't been real happy with my 94SE'* gas mileage. Car has 126K on it. I've been making several interstate trips lately and the average mileage is only about 20 with moderate in town driving. I just cleaned the throttle body and changed fuel filter. Air filter, O2 sensor, PCV valve, spark plugs have all been replaced within last 15K. Plug wires were changed at 75K. Tires are at 32PSI.

My check engine lite is not on but I've still thought of taking it to the dealer to have the codes scanned to see if it shows up anything that might be bad.

If my CE light is not on, does that mean that I have no codes or verifiable problems? I guess I would have expected my mileage based on past experience to be up into the 22-23 on avg. It always got about 19-20 in town and 26-27 on the hiway so 20 overall seems low.

Car seems to run well but mileage just doesn't seem to be where it should.

Any ideas would be helpful. I've read posts on fuel pressure and injectors. Are injectors hard to clean?

Thanks,

Mike
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Old 11-05-2004, 10:56 AM   #2
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Default Re: Does No Check Engine Light Mean No Codes or Trouble - Po

Personally, I clean my injectors with this stuff call Chevron Techron



I do this twice a year when I'm driving to my vacation destination.

As far as any codes stored even though your CEL did not come on. Well, I guess that means that there are no codes stored in the computer. If you have an Autozone near you, they might scan the computer for free(or at least a whole lot less than a dealer would.)
Is the car reaching the proper operating temperature? If the thermostat is defective it could cause a drop in mileage.
Also, if you're using oil that'* heavier than 10W-30 this would have an effect on your gas mileage as well.

I just read this from another post about stored codes

Quote:
Originally Posted by jr's3800
Sometimes the SES will not be tripped.... I have seen the PCM go funky and not trip the SES at all... But you get a battery of codes from thew PCM... Other times there is an SES the car runs like totall crapp and you get a battery of codes... <--- usually ends up a bad PCM... Also these cars will run without the Cam sensor signal, the timming will not be adjusted, the PCM will go into a default mode... Performance and effiency will be degreded, but the car will still be driveable..
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Old 11-05-2004, 12:26 PM   #3
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Default Does No Check Engine Light Mean No Codes or Trouble - Poor M

The engine is reaching operating temp and I ran a bottle of Techron through about 4000 miles ago.

I've thought about trying new plug wires but I hate to do that unless I can verify the problem. Autozone can't scan a 94 because it uses that funky hybrid setup - OBD1 with a 16 pin OBD2 connector. No one (not Autozone, Advance Auto, Oreilly, etc. can check it) except dealer can check it.

Regards,

Mike
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