My car is a 94 Nissan Altima (2.4 litre). What might cause it to consume huge amounts of fuel? (it uses up 3/4 of a tank on a 20 mile round trip across town - no traffic - no idling etc.). Other symptoms - runs very rough with diminished power - produces huge dense clouds of smoke that smell a bit like gas. This is a somewhat intermittent behaviour. There is a tiny exhaust leak either at the head/manifold or manifold/exhaust pipe connection. (the sound is similar to a bad muffler, but originates under the hood near the motor)
I have some suspicions - flakey electrical component (fuel controller?) or flakey injector.
My troubleshooting resources are extremely limited and some feed back to get me on the right track is greatly appreciated.
This isn't something simple to diagnose, especially if your skill at this are "extremely limited". It's not a -tuneup- or something like a fuel filter, sounds like a fuel injection sensor or computer problem. Make SURE you take it to someone who can deal with this sort of work and can repair it as well as diagnose it.
Someone suggested that an exhaust leak could cause faulty sensor readings leading to these sysmptoms. The car does have a leak at the mannifold to down pipe connection and I plan to change out the O-ring gasket(s). There's a lot of carbon soot at the joint. I wonder if it has contaminated the sensor as well and how I might clean it up.
Could you comment on that?
NK
Steve T wrote in news:c5rjjk$4ujr8$ snipped-for-privacy@ID-52908.news.uni-berlin.de:
Not and get 2-3 MPG. -Maybe- drop milage 1-2 MPG from normal.
Yes the sensor they are talking about is the O2 sensor and unless it's grounded (which I've never seen) it isn't going to do what you're talking about. When they get contaminated, the just stop working which most people would never notice the difference. Also this sensor is before the place where your leak is so would affect it anyway. DO NOT continue driving the car like this, running this rich can easily damage the engine.
Steve T wrote in news:c5si83$585t5$ snipped-for-privacy@ID-52908.news.uni-berlin.de:
This part is a bit puzzling.
20 - 25 mile used about 3/4 tank fo fuel. city drive - no idleing, light traffic and no fuel leak. So, allowing for a conservative estimate, lets say 35 miles and 1/2 tank of fuel. Something doesn't make sense.
Well, there's one lucky thing. The car has been sitting in my driveway all this time.
With good weather, and some luck with the nuts and bolts, I will have the O-rings changed out by this time tomorrow. I'll post back with results when it's done.
Uh your car is broken and it's not this exhaust leak you hope it is? You're not alone, most people hope it's something VERY cheap and simple to fix when their car is broken. Most of the time what they hope it is, isn't what's wrong. An exhaust leak won't make a car burn 3/4 of a tank of gas in
20 miles.
That's not the problem but you'll find that out for yourself tomorrow.. Ussually those kinds of exhaust leaks are due to broken studs, not bad gaskets.
And just some advice, don't keep running it and driving it like this, even to the repair shop. You can do THOUSANDS of dollar worth of damage trying to save a $40 tow bill. Hope things work out for ya!
They probably already ruined the cat driving it home blowing huge clouds of black smoke... Hate it for them but that drive home might have cost them several hundred dollars. I'm always amazed that people refuse to tow a car no matter how bad it's running or what kinds of noises they are making etc.
Steve T wrote in news:c5svd2$4ps6l$ snipped-for-privacy@ID-52908.news.uni-berlin.de:
Like you mention below, I am hoping for a simple problem.
Yeah. I figured there had to be more to it. So then, even a conservative estimate of 35 miles and 1/2 tank indicate bigger problems.
Steve I appreciate your feedback. Once I have the O-rings changed I can take it in for diagnostic with some measure of confidence the shop won't hose me.
thanks.
Yikes! Those can be very devilish to replace.
I have had it parked since the big smoke. (good to know I did the right thing.)
Steve T wrote in news:c5svn2$5etk7$ snipped-for-privacy@ID-52908.news.uni-berlin.de:
Hmmm. Glad you mentioned that. The smoke is white. I checked the collant and that seems fine. The level is full and appears to be antifreeze. I realize that the color of the smoke is significant and should have mentioned that in the first post. (mea culpa)
Funny, but I feel the same way. And now here I am doing just that. Dang! I just might be looking at a hard lesson here.
I had this happen on my first car (actually this was what caused the guy to sell it to me for $50). It burned half a tank of gas in 5 miles as I drove it home. Turned out to be a cracked rubber fuel hose between the filter and the engine. The gas was literally pouring out onto the road. I can't think of too many other scenarios that would use it as fast as you say. Are you sure the white smoke isn't raw gas pouring out of a ruptured fuel line onto a hot exhaust pipe?
"E. Meyer" wrote in news:BCA96EF0.68D34% snipped-for-privacy@ieee.org:
I have looked under the hood a few times and not noticed a leak. Neither is there any evidence of fuel on the ground. I might try to unplug a sensor or two but wouldn't know where to begin of if this is a good idea.
It's pretty wierd. I'm going to have another look tonight.
Steve T wrote in news:c62566$7838v$ snipped-for-privacy@ID-52908.news.uni-berlin.de:
Thanks for pointing that out. I won't do that.
Steve, You are right the exhaust leak is ablolutly not causing the fuel problem I'm experiencing.
I realy appreaciate all responses. The reason I posted here in the first place is to hopefully avoid creating a bigger problem. I need to do as much as I can on my own (within my means) before taking it in to the shop. Yes, I was hoping for something simple (remenbering the K.I.S.S. method), Just trying to check the simple and obvious to elliminate those first.
I assure all respondants that I have taken your advice seriously and you all have helped me out greatly.
Update:
Here's what I have found out so far. The exhaust leak is coincidental with the fuel problem as my repairs to the exhaust have had no effect on the fuel problem.
Earlier, "E. Meyer" suggested a fuel leak leading into the engine. I have taken a close look on the intake side and found no wet spots. But I have found what must be raw fuel in the exhaust and this leads me to believe that something is causing the engine to flood itself. It's not just running rich as there is liquid fuel in the exhaust. So, as one previous respondant suggested, I am lucky to have not blown up. Thanks to "clevere" for bringing that to my attention.
Ok. So now that the exhaust leak is not an issue (except that maybe it saved my life by venting the fuel before accumulating in the catalytic converter and muffler)
What might cause such a flooding contition where fuel is dumped into the engine at the astronomical rate of about 2 - 3 mpg?
Since it is fuel injected (I presume) I would bet either an injector is stuck open, or the fuel pressure regulator is toast. Either way, Instead of guessing, I'd take her down to a shop. Having that much fuel dumped into the engine can cause other funky things to happen ...
I suggested the exploding catalytic converter because it happened to me. I was running rich, and the converter heated up .. poof, blew the thing right up.
Besides that, all that fuel is washing the lubricating oil off the cylinder walls creating a very high wear condition for the rings/cylinders. Also the fuel is bypassing the rings into the crankcase and diluting th oil which can ruin the bearings and crankshaft/cams etc.
To the OP make SURE they change the oil when they get the problem solved and again DON'T try to drive it there and save the $50 tow bill!
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