I was on my way home from work (all highway driving) and my car started to buck/stutter/chug. I was going 65 mph when this started to happen but it would still do it at lower and higher speeds. Once I got onto the city streets it started popping and backfiring. My car has done this before but not this bad. The weird thing is that it would be just fine the next time I drove it. I have been getting a P0506 code - "Idle system low/Idle Air Control (IAC) valve responding" which I have cleared for the fourth time in the past two weeks. Could a bad IAC cause this much trouble and severe decrease in gas mileage?

Thanks,

Dave

 

Yes. Try pulling the IAC off and cleaning it. Could be gunked up pretty bad.

 

You also need to consider the relationship of the indicator to the actual
fuel in the tank. With these cars a 1/4 tank indicated is probably only
1/8 tank actual, or 2+ gallons. I consider the following with my car:

full = full
3/4 = 1/2
1\2 = 1/4
1/4 = get your a$$ to the gas station and fill up

 

I learned that the hard way.

 

I took that into consideration. The indicator was just below the half-way mark before my 30 mile trip home. That is still an excessive use of gas. I can even smell it in the cabin. I definately have something wrong because of the way it drives. I have auto tap but the battery on my laptop died on my way to work and I didn't get a chance to log my drive back home. I wish I would have. It probably would have shed some light on my problem. Thanks for your input.

 

I think we all did

 

Yeah, I found out that when it says 1/4 tank, I should go fill it up because with my first tank of gas, I ran it dry. I couldn't figure out why it was running like crap. Good thing it was in my driveway when it happened and I had some extra gas in the garage.

 

First week I had my car I thought I had a problem with the opti. Turns out it was on empty but the gauge read 1/8 tank You get use to it and you know when to fill up.

 

thats wierd, my car is the opposite way. i have ran it way below E and still have never ran out yet. Works for me!

 

If you can smell raw fuel I would check for leaks!! (cya)
I have a simaliar problem my gas guage , right now I have 130 miles in the first 1/4 of a full tank but if it goes a lil below a 1/4 it will suddenly drop to below E and if I fill it with 4 gallons it jumps up to a 1/4 tank

 

Your rather lengthy signature doesn't mention if you have a CAI. So do you?

97 WS6 A4 w/3.73's
Cam (236/242 .555/.576 112+4 LSA), Hooker long tubes w/no cats, Comp R lifters, 1.6 NSA pro-mag rockers, double roller, ORY, Flowmaster American Thunder Exhaust, Meziere water pump, 160 thermostat, PCMforless tune, LT4 knock module, Widened stock rims to 11"

 

I have the stock ram air hood and air box. What difference does that make?

 

Several folks use CAI's and every once in a while, one of them has a leak in the box where the air filter sits. Go through a good rain and see where this is going?

 

if it isnt the iac when was the last time you changed the opti. After some driving the optical spark sensor neer the crank starts to heat up and causes it to read wronk. this is what happened to me.

 

The night I bought my car it ran out on me pulling into the gas station. Was right above 'E' if I remember right.