MPG has gone to crap

7upstang91 · Jan 22, 2010

I used to get about 160 miles to the tank to about 170 with the stroker. Now the past two weeks the car has gotten horrible gas mileage. About 130 miles before I fill up. Today at half a tank it was at 60 miles. Sooo crap. Every once in a while I smell raw gas(the past three days). I have looked for gas leaks but haven't found any. So what could be the problem. I did recently find out the guy who tuned it sucks and can't tune worth a flip. Pretty pissed about that, but that shouldn't cause bad gas mileage right? It was tuned two years ago. Any ideas on where to start?

90mustangGT · Jan 22, 2010

Did you check it for codes? How is it running otherwise?

KamiKaziDK · Jan 23, 2010

Check your fuel rails and injectors while the motor is running, if you can smell gas it's possible they're leaking and you can't see it because the fuel evaporates before making it off the top of your engine. I would get it re-tuned also though....even with the stroker you should be getting better than 11-12 mpg unless you've always got your foot in the pedal.

7upstang91 · Jan 23, 2010

KamiKaziDK said:
Check your fuel rails and injectors while the motor is running, if you can smell gas it's possible they're leaking and you can't see it because the fuel evaporates before making it off the top of your engine. I would get it re-tuned also though....even with the stroker you should be getting better than 11-12 mpg unless you've always got your foot in the pedal.

I honestly hardly ever have my foot in it, there is never a need for it. No kidding I found out the other week that the guy who tuned it, can't tune EFI to save his life. PISSED ABOUT THAT. Nothing like $400 for basically a couple dyno pulls, but I was young and stupid and didnt know much about tuning. I did look the other day and couldn't see anything like you said I wouldn't be able too. Would the codes tell me for sure? How am I really going to know if they are leaking from the injectors?

90mustangGT · Jan 23, 2010

You are probaly running pig rich. It could be as simple as oxygen sensors/sensor that has gone bad. How was it tuned? Aftermarket ECM???

7upstang91 · Jan 23, 2010

Since the tune sucks I have never know how the car should really run I guess. But compared to the past it bogs until it warms. Not bad at all, but I notice. Once its warn it drives fines. At idle the RPMs have dropped about 200, now sitting at 800 instead of 1,000. WOT it runs great(but the car has seen that twice in two weeks). My buddy has a code puller so I'll have to get to his shop soon. But the car does randomly SHAKE, even while driving or sitting. It will shake for two or three seconds then stop. Idle is fine and does this under driving and braking conditions.

banks · Jan 26, 2010

we'll check everything over next weekend, i should have some time on saturday we can take a good look at everything and try to figure it out. when was the last time you changed the fuel filter?? also i think i have the stuff to look at the comp parameters and we can look at the 02 signals to make sure they are working properly. I can't remember but does that car have the OBDII port in it or is it something different. I can't remember when they started doing the OBDII stuff

tannerc91gt · Jan 26, 2010

It's obdI.

Sound to me like you're in serious need of a tune. A bad tune is worse than no tune IMO

7upstang91 · Jan 26, 2010

Looks like its gunna be parked until I get money for new heads. Crap, seriously if I see the guy who tuned it ever again...I might end up in jail. I know its running rich but didn't think that rich.

But the gas mileage was much better after I let the car sit the whole weekend.

banks · Jan 27, 2010

tannerc91gt said:
It's obdI.

Sound to me like you're in serious need of a tune. A bad tune is worse than no tune IMO

bummer, i don't have the stuff then..

7upstang91 · Jan 27, 2010

darn. Time to buy an air/fuel gauge. When we take it apart should we have the AFR's ported?

7upstang91 · Jan 27, 2010

EGR is stuck closed. So needs a new one and still a TUNE!

banks · Jan 28, 2010

7upstang91 said:
darn. Time to buy an air/fuel gauge. When we take it apart should we have the AFR's ported?

depends on how much money you wanna spend there. i would have someone like TEA professionally do it, but that gets pricey.

MPG has gone to crap

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