Any Ideas? I know it's not going to be great but that is horrible! I know my knock sensors need to be replaced. Would that cause such a substantial MPG?

My hwy miles are still only maybe 16/17 at best. Any ideas? Should I just start with replacing the O2's and knock sensors? I am not throwing any codes other than the dead knock sensor things.

My mileage improved tremendously with new (used) injectors and a new (used) MAF. I went from 8mpg city to 12mpg city. I went from 14mpg highway to 19.5mpg highway.

guadofreak wrote:Any Ideas? I know it's not going to be great but that is horrible! I know my knock sensors need to be replaced. Would that cause such a substantial MPG?

My hwy miles are still only maybe 16/17 at best. Any ideas? Should I just start with replacing the O2's and knock sensors? I am not throwing any codes other than the dead knock sensor things.

Seems like you have some of the answers right here.

Knock SensorsO2 SensorsMAF (clean at least)BG44K (1 can to 1/2 a tank)Ohm injectors

How dark is your exhaust tips?

I'm getting something like 15mpg city and 20 highway, maybe 18 combined. That's on Shell V-Power 92.

First thing is to check your injectors make sure they arent leaking..

A Q should be able to get 18mpg AT LEAST with shot o2 sensors, KS have no impact on mileage.. Start by cleaning everything, MAF, TB, etc, make sure the car isnt running warm... Also toss some BG44k in there.....

Before I replaced my knock sensors, the car was hesitating very badly and I know it affected my mileage because even cruising along at 65 mph, you could feel the car missing/bucking/hesitating slightly. I know as bad as the car was running, it certainly didn't help my mileage.

Replaced the MAF a while ago. but the used one i got I think is going bad again...however mileage stayed the same. There is no gas smell so that should rule out that.

I will figure out how to ohm the injectors and do that thursday maybe. Waht's the range again?

I will order a can of BG44K and have it delivered for thursday.

And go ahead and clean the MAF hopefully that is all it is.

Also my exhaust tips aren't bright and shiney but aren't nasty black either. I will double check tomorrow though.

thanx again

replacing the O2 sensors will give you a noticeable, significant increase in gas mileage per gallon, trust me.

"KS have no impact on mileage."

Like saying ignition advance has no impact on mileage?

Full advance [just short of serious knock] can only occur with functioning KS..............otherwise you get a less than optimal advance thus efficency at steady cruise is way off the mark. Probably no more than 10% loss in steady state mileage..............say 20 vs 22 at 60 mph

O2 sensors can only trim the preprogrammed [MAF/load/rpm/coolant temp/tps] injector open time by +- 20%...........however if O2 switching doesn't occur the ecu just uses thee preprogrammed value so at best new vs old O2 MIGHT VARY BY 10% MPG at cruise.

Both might be additive depending on other variables.

The Q was rated at 22 mpg with premiun fuel on EPA Rural Highway test [no more than 61mph, no AC. tires at 35 psi].

Not unusal to hear of/see them at 18mpg needing O2 and KS repairs.

Generally a bad/dirty MAF will show less than true airflow so within the 20% without proper O2 the mileage might get a tiny bit better until the lean knock surfaces.

You would never know [except highway mpg] a 10 % too rich condition [13 vs 14.7] but a 16.1 AF would knock like crazy.

When signals are not as preprogrammed the system always self protects by throwing more fuel and less advance at the problem........the double whammy shows up as a serious drop in mpg.

{Using my backup name q45tech2 ..............not much time these days always seem to have password trouble when away from home}

I'd love to get 14.9! I get about 12 around town, but I realise that's mostly due to my lead foot and joy of the V8 rush. I get solid 20 on fwy's with air on, at 80-85. I just wish it was better around town.

Me too. Probably need new 02 sensors as well but my car is running strong and I too enjoy the V8 rush!

I dont really care what my in town mileage is... Ive seen 14, ive seen 10, it really doesnt matter... What ive found that it really depends on your driving cycle.. LIke if you only drive 7 miles, then of course your going to get crappy mileage.... I just care what i get on the highway, which is 19-20 or so....

Have you done the test on the Oxygen sensors? It is right past the section on checking the codes with the car off. You go throught Mode I, then start the car, and do Mode II with the engine running. It tells you if the O2 sensors are lean or rich. A bad O2 sensor could cause poor gas mileage, amont humdreds of other little things on the engine.