playmakr

Wife's driving the 95quattro to work, puts 87 unleaded gas in the car - sometime later, tells me that she's at the service station getting the car checked out because it's hesitating. While she's at the station the mechanic tells her that it's the cat?? First thing i think of is that maybe it's the 87octane (btw, this was not the most reputable of gas stations where she filled up), the next thing i think of is that maybe there was some water in the tank? i get some stp fuel cleaner and some techron - i also put in some gas-line anti-freeze just before it runs out of gas and put in 5gallons of high-test. Now the car still "misses" (a little) throughout the rev range 'till about 4500k then smoothes out (or is not audible because of wind noise/road noise/mechanical noise, etc.). It has roughly the same amount of performance, but has rough idle and is nowhere near as smooth as normal. i bought this car about 5k ago. could this be the cats (as per shady brooklyn mechanic)? oxygen sensor? gasket in throttle body? plugs? fuel filter?

dimeadip

However, I always use a reputable brand of gas. But, the primary thing differentiating reputable and "cheap" is the addition of detergents and additives. The fuel itself is most likely the same. (At least according to the head chemist in the analytical lab I spoke with at one of the country's major refineries)

CvTech

put a fuel treatment in and continue using the octane that you used to use. I read somewhere a while ago that nothing below 91 octane should go into these cars.

To dimeadip - if thats what yuou've been running, your car is now "accustom" to it.

Hokie - STI avant

I tried 91 once and it wasn't the best experience.

Mike

CvTech

yeah I only put 93 un my car as well, runs pretty bad otherwise

Catamount90

I've run 87-83 in my 1995 90Q and noticed hardly any differences

playmakr

hmmmm.....to be more specific - the car sort of "flutters" it's way up through the rev range. Does anyone know if this is one of the symptoms of a cat needing to be replaced?

TabulaRasa

Take a stick, go under the car and hit the cat with the stick. If it rattles, it's bad. Your car has two cats, mounted side by side.

TabulaRasa

The ECU is used to running on crap gas so it has pulled back the timing.

My ECU is used to running on 93 and if I suddenly put 87 in it, it'll throw a CEL and run like crap.

oddBALL

lol.