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Discussion Starter · #1 ·
My car started running pretty rich about a few weeks ago. I commute to and from school and work with an average of around 50 miles a day, and a full tank would last me from Sunday til Friday without even red-lining. So about 300 miles a tank, mostly city. Now I get barely 200 miles a tank :/

I've looked through the threads and found a few things that might need to be checked, but the only difference is that almost everyone on here has a modded lude. Whether it's got a ton of mods or was just a p.o.s. in general, they don't seem to have the same problems as mine.

The running rich is the ONLY (new) problem that we can see. My car is in great shape, I've been driving it for almost a year, maintenance every 3-5k,barely any problems AT ALL. It's almost COMPLETELY stock, only difference is that we put in an AEM intake about a month ago. The intake is fine, clean filter. The car isn't giving any codes, hasn't had any issues with the engine, hasn't been getting hot. There is one other problem, but one that its had since we got the car back on the road, and that's a really small oil leak from near the oil filter, and it only leaks when the weather is cold, which was when we first started driving it and now. It was perfect all summer.

So where do I start? What do I need to look for? I really need to get this taken care of, I can barely afford to drive the car as it is, paying for college and whatnot, I'll be so sad if I have to start taking the motherfucking bus :wzbigcry: Help?
 

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how rich? at what rpm does it become noticably richer? do you have a wide band to hook up and get a reading?
 

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I'd start small. start with replacing the fuel filter. could be overdue. Then maybe check for vaccum leaks. Even small ones that might not cause idle issues but the computer might be trying to adapt to a leak causing it to add more fuel. I'm not sure where to go from there but that is where I would start.
 

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Your absolute best bet is to have an obd2 scanner connected and actually seeing what each sensor is reporting. This will most definitely get you right on track to finding out why. That is if you have easy access to one and your willing to do pleanty of research after obtaining that info.

Btw i highly suggest addressing the oil leak you mentioned. Oil leaks in that area are no good. Oil in that area is under pressure so a small seap can easily become a gusher very very fast. Before you know it...no more oil in the engine.
 

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Discussion Starter · #7 ·
@bouckarooo: Rich enough to have black exhaust. No idea what rpm, everything seems completely normal, save for the gas mileage and exhaust. We dont have anything at my place to hook it up to and check it out, but my dad works at an autobody shop, and I have friends that have anything I would need. Just need to find the time. Thank you!

@buying5thGen: Alright, thank you for the suggestions! I'm hoping it's something small, since nothing else seems to be affected.

@hatedenemy: Okay, I'll be sure to get that done, I can definitely find a scanner to connect on.
And the oil leak is actually something strange, we've used the machine that tests for oil leaks on the car and it reports that there isn't an oil leak, but there's still oil (and yes, motor oil, not any other fluid, we've made sure) that drips down from somewhere...

Thank you everyone! I really have very very little experience with this stuff, but I'm slowly learning!
 

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What machine did you hook up to find the leak? It clearly isn't reliable if you can visually see the oil but it giving you a negative.

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Okay. Take some time to clean up the oil. Basically any oil and dirt on the outside of the engine. Drive. Then check from the top working downward looking for leaks.
 

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When you get a scan tool hooked up to it, watch your O2 sensor in real time. It should be switching from around 200mv-800mv back and forth, this is normal. However if its stuck on the low end around 200mv and doesnt switch much or at all then either the O2 sensor needs replaced or you're getting a lean condition such as a vacuum leak. When that happens you will dump fuel to try and compensate. Also look at your fuel trims, im willing to bet short and long term are way in the positive like +15% or more if you're getting black smoke.

The fuel filter has nothing to do with running rich, if anything that would be a reason why you'd be lean, but you dont have that problem. I would also check the fuel pressure regulator, its vacuum operated so make sure the vacuum line is connected properly. When the FPR goes out, your fuel pressure increases by a good 10psi or so which will spray more fuel than needed.

Also you could have a leaky injector, but thats not a common thing at all so unless you're out of ideas i wouldnt worry about this but keep it in mind.
 

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@bouckarooo: Rich enough to have black exhaust. No idea what rpm, everything seems completely normal, save for the gas mileage and exhaust. We dont have anything at my place to hook it up to and check it out, but my dad works at an autobody shop, and I have friends that have anything I would need. Just need to find the time. Thank you!

@buying5thGen: Alright, thank you for the suggestions! I'm hoping it's something small, since nothing else seems to be affected.

@hatedenemy: Okay, I'll be sure to get that done, I can definitely find a scanner to connect on.
And the oil leak is actually something strange, we've used the machine that tests for oil leaks on the car and it reports that there isn't an oil leak, but there's still oil (and yes, motor oil, not any other fluid, we've made sure) that drips down from somewhere...

Thank you everyone! I really have very very little experience with this stuff, but I'm slowly learning!
You need to make time and have somebody hook up an obd2 scanner to report back the info here. As many suggested already, the o2 sensor/clogged cat is common issue when running rich.
 

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When you get a scan tool hooked up to it, watch your O2 sensor in real time. It should be switching from around 200mv-800mv back and forth, this is normal. However if its stuck on the low end around 200mv and doesnt switch much or at all then either the O2 sensor needs replaced or you're getting a lean condition such as a vacuum leak. When that happens you will dump fuel to try and compensate. Also look at your fuel trims, im willing to bet short and long term are way in the positive like +15% or more if you're getting black smoke.

The fuel filter has nothing to do with running rich, if anything that would be a reason why you'd be lean, but you dont have that problem. I would also check the fuel pressure regulator, its vacuum operated so make sure the vacuum line is connected properly. When the FPR goes out, your fuel pressure increases by a good 10psi or so which will spray more fuel than needed.

Also you could have a leaky injector, but thats not a common thing at all so unless you're out of ideas i wouldnt worry about this but keep it in mind.
^^^ post of the week right here
 

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It should be throwing a code po420? I think for insufficient cat? But your not throwing any codes right? Don't reset the ecu until you've diagnosed the issue.

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Discussion Starter · #16 ·
update sorta

so here's something new. got my oil changed/new filter, and now the gas mileage is back of to 320 miles per tank (kinda weird), exhaust still dark as far as i can tell, car smells hot but isn't, and the power steering fluid is leaking from the bottom of the reservoir. looks like there's some indentations on the reservoir itself, and might need a new hose. also looks like a bit of oil drips out of the oil filter, but it might just be loose... plus both the p.s. fluid and the oil seem to be really thin, so that might be a bit of an issue... and still no codes.

also, we first tested the car on the oil leak sensor almost a year ago, and i drive the car a lot, so an oil leak may have developed since. i'm going to have it run through the machine again this coming week...

thanks for the suggestions, everyone! I'm going to get everything checked out tomorrow, since there's apparently no school in honor of veterans day...
 

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I think youre wasting money on whatever oil leak machine youre interested in. Basically most of any oil leaks commonly encountered makes its way around the backside of the engine.

There is an oil leak thread that highlights key areas. A clean engine makes for finding leaks very easy.

Black smoke may be soot from the exhaust. Exhaust tumbles around at the back bumper from aerodynamics of the car. This does create black deposits on the bumper. This could be from oil as well. Stock pcv system does a nice job of putting oil in the intake and gets burned. Leaky valve guides cause the similiar effect too. You may notice less deposits if you have an oil catch can installed.

You said it smells hot. Do you mean you smell oil burning? Your oil leak might be dripping onto the flexpipe. Im certain this will leave deposits on your bumper too. You think the oil is thin and you just had it replaced? Check the coolant. Which brings me to asking what oil you use? Interested in type and weight not so much the brand name.

Id like to add that i dump black soot on hard accel sometimes and my fuel trims are under 10%.


Honda published a TSB regarding black smoke from exhaust.

But i should add that you should still interest in knowing what the LTFT and STFT are doing. Im simply presenting another possible scenario, one without o2 or fpr issues. Your MAP sensor plays role too.
 

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Discussion Starter · #18 ·
I think youre wasting money on whatever oil leak machine youre interested in. Basically most of any oil leaks commonly encountered makes its way around the backside of the engine.

There is an oil leak thread that highlights key areas. A clean engine makes for finding leaks very easy.

Black smoke may be soot from the exhaust. Exhaust tumbles around at the back bumper from aerodynamics of the car. This does create black deposits on the bumper. This could be from oil as well. Stock pcv system does a nice job of putting oil in the intake and gets burned. Leaky valve guides cause the similiar effect too. You may notice less deposits if you have an oil catch can installed.

You said it smells hot. Do you mean you smell oil burning? Your oil leak might be dripping onto the flexpipe. Im certain this will leave deposits on your bumper too. You think the oil is thin and you just had it replaced? Check the coolant. Which brings me to asking what oil you use? Interested in type and weight not so much the brand name.

Id like to add that i dump black soot on hard accel sometimes and my fuel trims are under %10.


Honda published a TSB regarding black smoke from exhaust.
Not wasting money on oil leak machine thing, my dad's work has one and there's no charge for us to use it. The car smells like its burning oil, but there's a small drip beneath the radiator (just got back from poking around. p.s. leak is to the point that we have a rag stuffed in there at the moment) burning smell doesn't smell like coolant though (doesn't have that weird sweet smell to it, at least)

As for the oil, normally my family changes our oil ourselves, but I didnt have time, so I got my oil changed at the dealership I work at, and I just checked the receipt and the guy who changed my oil put in 5w-20 in lieu of 5w-30 :| I always have good quality 5w-30, and i know our dealership carries it, idk what the idiot put in 5w-20. a full-on sudden switch can't be good for the car, can it?

:(
 

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cleaning the egr valve is a service item might help with the mpg, and the oil leak could be that they put the filter on dry. A common problem you need to rub a little oil into the seal before fitting.
 

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I wouldnt use 5-20, i would stick with 5-30 or even 10-30 if its hot where you live.
 
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