I was "kicking the tires" on a few beater cars for sale locally here. One of them the owner said the car was running well, but was having very high fuel consumption. i.e. it was getting about 1/2 the fuel mileage it probably should. When he started it, the engine sputtered a bit at start up but then idled and seemed to rev OK. But you could definitely smell unburned fuel. No fuel leaks noted.
My first guess is fuel regulator. Any other causes? I know timing and such can alter fuel economy, but if it's getting literally half what it should, something else is going on...
Clogged injectors, bad injectors, timing advanced or retarded, bad cam timing, hasn't been driven in a long time--see clogged injectors, O2 sensor bad, computer dying, bad wiring to computer, bad/old plugs, wires, coil, coil pack(s), vacuum leak(s), ....help me out here...
mndsm
Dork
11/2/10 10:12 a.m.
If it's smelling like gas, and runs fine, it's probably dumping fuel. Now the question is- why? On my ms3, it'll dump fuel whenever it thinks it's going to go lean, and end up belching out a big ol' cloud of black smoke before the ECU catches up and says "Ok, we aren't going to asplode". On an older car... I guess it would really depend on how old. Faulty knock sensor (if the car was so equipped) could trigger a rich condition and send the fuel system into overdrive. Car could have also triggered limp mode (again, depending on equipment) which would cause it to pull timing and likely run REALLY rich, as a means of self preservation. Has the car in question thrown any CEL's? Any sensors are as likely to go bad from sitting as they are from being worn, and the combination of the two would almost certainly cause them to foul....
Also, what Triumph says. If the car is OBD compatible, I'd get a hold of a scanner, and see if it's throwing any codes, and work from there.
I had a VW do that. Turned out to be a coolant temp sensor.
Coolant temperature sensor?
I had a k-car that did that - turned out to a blocked EGR. 02 sensor can do it too.
So there are a lot of different possibilities to look at. I didn't see an CEL on, and I dn't have an OBD scanner. I'll have to see if I can get my fingers on one.
I didn't see any major smoke clouds at start up. It was cold outside, so there was minor condensation, maybe a touch of black smoke, but that was it. It sputtered a little, then settled into a normal idle. Definite smell of gas. He said the fuel mileage had been poor for a few months.
I once forgot to plug the MAF back in on my Legacy and got about 10mpg, but the car ran fine.
Wonkothesane wrote:
It might help to know the make/model/year of the car as well...
yeah this. If it's an RX-7 well then that's the problem right there!
If it runs ok and still a gas smell. Look for leaks.
1988RedT2 wrote:
Coolant temperature sensor?
The starting mixture is richer than normal.
If the temp sensor has failed and is constantly reporting a cool situation, it will cause the computer to not switch to a leaner "hot" setting.
Basically an electronic version of running with the choke on.
egnorant wrote:
1988RedT2 wrote:
Coolant temperature sensor?
The starting mixture is richer than normal.
If the temp sensor has failed and is constantly reporting a cool situation, it will cause the computer to not switch to a leaner "hot" setting.
Basically an electronic version of running with the choke on.
Had a v6 cavailer do that one...
I know when my aurora was running in open-loop? my mileage went from 20mpg to 8mpg.
Something about 8 Fuel Injectors firing all the time vs just the correct one
When I got my 9000 Aero, the upstream O2 sensor was reading extremely lean... as such the ECU was all like "Whoa now... MOAR FUELZ" which is great, except that the car wasn't actually running lean. Averaged 14mpg.
Replaced the sensor and now average a happy 28-32.
