Gas milage problems

[JohnsMyName]

So at $3.60 a gallon for 93 I am getting tired of my bad gas milage. The car used to get between 17-23 when I first baught it (4 yrs ago) deppending on how I drove it. Now Im getting 11-13 mpg I've done plugs, wires, oil, and fuel filter regulary so I know its none of that jive. Car is stock except for what the sig says with 68k on the clock, please help.

 

[98 Saleen Cobra]

Clean the air filter if you haven't, clean the MAF, I'm not to sure about this one but maybe clean the IMRC's.. Other than that I'm not to sure what else it could be.. I just filled up and I averaged 20mpg city and highway....

 

[JohnsMyName]

I have a new filter and cleaned the maf maybe 2,000 miles ago. Also tire preasure is perfect, I dont get it? I am getting a check engine code for P1443, it's an evaporative emissions control. I doubt this is related however because the light goes off and on, and has been around longer than this problem.

 

[Cocoloco]

I think someone is stealing your gas???

 

[03CobraDom]

It's probably that 10lb weight you have attatched to your right shoe...

 

[JohnsMyName]

It's probably that 10lb weight you have attatched to your right shoe...

Thats what I thought cause I've been living in the city since I took it out for this year, but I went on a road trip and even two hours on the highway still produced horendus mpg.

 

[cobraless1]

I just cleaned my IMRC's and changed my old conventional oil to royal purple synthetic a couple days ago and went from getting about 13-16mpg to getting 21-24 now.

 

[Slow95Cobra]

fix the engine lamp.

 

[96svtsnake]

The CEL will cause the car to go into safe mode and run richer than stock. Definately fix the check engine light.

 

[Gallows]

I have a new filter and cleaned the maf maybe 2,000 miles ago. Also tire preasure is perfect, I dont get it? I am getting a check engine code for P1443, it's an evaporative emissions control. I doubt this is related however because the light goes off and on, and has been around longer than this problem.

But it could be making your mileage worse as time goes on. I'd look into getting it fixed.

 

[98 Saleen Cobra]

+1 check the CEL and get it fixed.. also change the oil to synthetic and clean the IMRCs..

 

[JohnsMyName]

For years I've been reading about the IMRC cleaning, but didn't want to open a can of worms. How difficult is it really and does it make that big a difference at 68,000?

 

[mrspeedy69]

For years I've been reading about the IMRC cleaning, but didn't want to open a can of worms. How difficult is it really and does it make that big a difference at 68,000?

Yea i've been reading about everyone cleaning them. I've just been a little afraid to tear into it...

 

[qkslvr221]

The CEL will cause the car to go into safe mode and run richer than stock. Definately fix the check engine light.

I think that's only if it's VERY serious, I seriously doubt something like the rear o2's would cause a limp mode.

 

[na svt]

Cleaning the IMRCs will do nothing since the secondary's aren't open while cruising down the hwy anyway. For example, I know of a Mark VIII that has 120k on it and has never been over 3000rpm, never had the IMRCs cleaned but still gets over 20mpg on the hwy.

 

[Slow95Cobra]

I think that's only if it's VERY serious, I seriously doubt something like the rear o2's would cause a limp mode.

not always.... if anything is keeping the car from going to closed loop, it will ignore the 02's and cause bad gas milage. say is the rear 02's say 0 or .03 volts, then its saying, "hey I'm lean, gimme all the fuel you can to fix it".... then more gas=crappy mileage.

 

[qkslvr221]

not always.... if anything is keeping the car from going to closed loop, it will ignore the 02's and cause bad gas milage. say is the rear 02's say 0 or .03 volts, then its saying, "hey I'm lean, gimme all the fuel you can to fix it".... then more gas=crappy mileage.

I'm pretty sure only the front o2's control lean/rich, and the rears are just there for catalytic efficiency checking.

 

[cobraless1]

Cleaning the IMRCs will do nothing since the secondary's aren't open while cruising down the hwy anyway. For example, I know of a Mark VIII that has 120k on it and has never been over 3000rpm, never had the IMRCs cleaned but still gets over 20mpg on the hwy.

When you clean the IMRC's you usually also clean the intake hat, the inside and outside of the runners, and the throttle body, all of which I would think could increase gas mileage even while cruising down the highway.

 

[na svt]

When you clean the IMRC's you usually also clean the intake hat, the inside and outside of the runners, and the throttle body, all of which I would think could increase gas mileage even while cruising down the highway.

I hope you aren't cleaning a TB with the same stuff you clean the IMRCs. Also, I've had about 30 96-98 intakes apart and none of them were dirty enough to affect mileage.

 

[Slow95Cobra]

I'm pretty sure only the front o2's control lean/rich, and the rears are just there for catalytic efficiency checking.

it really depends on the problem. you would think if rear 02's are flat, it would throw a cat. eff. code, but it doesnt, just depends on fuel trims and other things. i was just making a point that engine lamps are on because there is a problem with the emmisson system, and can affect gas milage. not tryin to bust ya chops man :thumbsup: