My Mustang is giving me 100 miles less than normal

Hello,

I own a 1999 V6 3.8 Mustang and with a full tank (about 15 gallons) I would normally get around 310 miles. Currently, I'm only reaching 200 miles with a full tank of gas(also, the service engine light is on). I took my car the shop and they said I have an exhaust leak (something to do with the gaskets). the mechanic said he will fix it plus clean the fuel injector(s), change the spark plugs and cables. In addition, I asked him to change the oil, oil filter, the gas filter and a smog check which I need to do.

To the best of my knowledge, I can visually verify that he did change the oil and filters, spark plugs and cables. Not sure if he cleaned the fuel injector(s) or the exhaust but i can tell my car runs better. But it did not have the punch that i remember when i last gave it a tune up. He did not perform the smog check because it was 8pm Monday, i needed my car to go to work in the morning (i had to have my car for the next day)AND he said that he needs to drive the car for

30 min. in order for the computer chips to reset in the car. Is this true?

So the following morning (Tuesday) the service light came back on and on Friday night the car was running like shit. Not only was the service light on but it was flashing my car had little power, and when my car was on park it was rocking back and forth. I took it back the next day and he said a portion of a spark plug cable (or a different cable) touched a hot spot and shorted out. I get my car back, it runs get and with the punch i remember it use to have. but still no smog check. he gave me the same story, need to run the car for 30 mins. Anyways, the next day the service light comes on and it's still not giving me the maximum mileage after one week of driving.

What can cause this mileage problem i have? Note, that i have not change the gas type or location where i buy the gas or had my smog check yet.

Thanks in advance for your opinions.

Best Regards,

R
Reply to
SonicStructures
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Yes, the ecu needs to get a set of parameters and such to optimize the engine. Same reason you cant get an OBD2 inspection to pass by resetting the ECU. My Dodge has to go about 50 miles to get a good set of registers to pass.

Might take several tanks to get the ecu back to optimal settings.

Reply to
RM v2.0

the drop in gas mileage is because of the service engine soon. the computer goes into limp home mode and gas mileage sucks. Take the car back and get the work done or complete it yourself. You definitely need to get the Service engine soon error fixed. get the code from the computer and figure out what the sensor's is telling you.

Reply to
Les Benn

Service engine lite is serious get the code read out. you can do it yourself too.

Reply to
bob

The 2006 owner's handbook describes a set of operations required to reestablish the computer's logic. It includes such items as twenty minutes in 40 mph traffic with one-minute idle periods interspersed (not exact, but like that) as well as an uninterrupted ten minutes at

50 mph or more (or some such). I know I was amazed when I read that, but now I can't seem to find where.

Who says computers don't govern our lives?

Reply to
Frank ess

You sure about that? I understand there is a limp home mode but I dont think it is always triggered. I see that light on in lots of cars and they get the same mileage as before, might just need minor servicing.

Reply to
RM v2.0

They dont govern my......oops, got email, gotta go.

Reply to
RM v2.0

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