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Old 04-06-2009, 07:39 PM
 
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So I am driving one day and my check engine light came on... At that time, I was trying to park by driving slowly into a parking spot hence the low rpms. The engine "felt" like it was having a hard time with getting enough fuel and the "check engine" light came on... So I brought it over and they said the computer code is "lean fuel" and I thought its probably cause of the cheap fuel I keep buying... I put in some bottle of fuel injector cleaners into the gas on the first fill-up... and the Autozone guy resetted the light... it stayed off for about a week when my gas tank was half full and the same thing happen when I am parking again and the check engine light came up... at higher speeds, I don't notice any problems... so what's the problem? Fuel filter? Something else? Cheap gas?
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Old 04-06-2009, 08:14 PM
 
Location: MI
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Could be any number of things, filter,fuel pump,throttle postion sensor, etc. Some cars have a shrader valve on the fuel rail where you can check pressure with a gauge, I just depressed my valve w/o gauge and could tell I wasn't getting enough pressure. Have A-zone guy pull codes it should be more specific than lean fuel.
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Old 04-06-2009, 08:15 PM
 
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Fuel filter;with the electric i tank pumps you never want it dry because it will eventually go out. My guess is fuel fioletr first if not cvhange at intervals recommended. If the butter fly valve needs cleaning on the injection ; that might do it;have the system cleaned that includes spraying the butterfly.Electric i tank pumps are bad about eventually going out if you ever run the pump dry;good reason not to run out of gas.Other than that the injection system electornics.that is just what i have seen.
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Old 04-06-2009, 08:22 PM
 
Location: San Diego California
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Quote:
Originally Posted by evilnewbie View Post
So I am driving one day and my check engine light came on... At that time, I was trying to park by driving slowly into a parking spot hence the low rpms. The engine "felt" like it was having a hard time with getting enough fuel and the "check engine" light came on... So I brought it over and they said the computer code is "lean fuel" and I thought its probably cause of the cheap fuel I keep buying... I put in some bottle of fuel injector cleaners into the gas on the first fill-up... and the Autozone guy resetted the light... it stayed off for about a week when my gas tank was half full and the same thing happen when I am parking again and the check engine light came up... at higher speeds, I don't notice any problems... so what's the problem? Fuel filter? Something else? Cheap gas?
As a general rule, a problem with a fuel filter, or low fuel pressure is going to be more evident when the engine is under load, like climbing a hill or heavy acceleration. If it is happening while parking it seems like something affecting low speed/idle operation. Have you ever cleaned your throttle plate? When throttle plates are dirty it sometimes causes a low reading at the MAF sensor, which in turn causes a lean mixture at low rpms. MAF sensor contamination is also a possibility. If you are able to disassemble the MAF sensor, there are 2 wires (a ref wire and a signal wire) that can be can be cleaned with compressed air. If neither of those corrects the problem, you are probably going to need a professional diagnosis, as you are possibly looking at a vacuum leak. Many newer vehicles have composite intake manifolds and are prone to leakage. If that is the case it will require resealing the intake manifold.
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Old 04-06-2009, 08:25 PM
 
Location: Eastern Washington
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It probably would not hurt to try a good name-brand gas. How old is your fuel filter? How many miles on it? If you don't know, it's worth changing it. I have documented about 5% fuel economy improvement on a couple of cars when I changed fuel filters that were past due, these cars did not have a CEL lit up.

What make, model, and year is this car?

Interesting that this is happening only at low speed, usually an overdue fuel filter will give trouble at high load as well.

What *may* be happening is that at low speed, your system voltage is falling off (alternator is not making up for the electricity the system is using) so voltage at your fuel pump is falling off enough that it can't make enough pressure. This is, of course, no more than a SWAG...

Yeah, if you can get more information from Auto Zone than "lean fuel" ie post the exact code number and the complete description, that may help some of the pro techs on here zero in on what's going on.

Running a fuel filter way beyond it's replace-by miles will cost you more than it's worth - your mileage generally is not as good as it should be, and it makes life hard for your fuel pump, which is not as cheap to buy or easy to change as on a car with a carburator...

texdav makes a good point, don't intentionally run a car with FI below 1/4 tank of fuel, the fuel cools and lubricates the fuel pump...
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Old 04-06-2009, 08:51 PM
 
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It is 1998 Honda Civic with only 70k miles on it... fuel filter has never been changed... the car performs fine otherwise... I will ask the autozone guy the exact code number later and post it here.... thanks everyone!
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Old 04-06-2009, 10:22 PM
 
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Iam kind of surprised that the engine hasn't starved out before this with that old a filter. Apparently the gas used has been pretty clean.Might want to pay attention to the owners manual maintainence schedule for best performance and life.
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Old 04-07-2009, 04:43 PM
 
Location: Eastern Washington
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The fuel filter is overdue and should be changed, but I doubt that this is the *only* problem. The throttle plate, as noted by jimhcom, probably needs cleaning too. You will probably pick up some MPG if you change the filter, I usually see an improvement when I change an overdue filter like this, even if the car is running "fine" and no CEL. As the fuel filter gets more and more plugged with the stuff it's keeping out of your injectors, the resistance goes up and on all cars that I know about the fuel pump has to work harder, that is, it draws more amps.

FWIW this thing has only 4 sparkplugs and if they are also original, you might be surprised how much better it will run with new ones. Most Hondas are very easy to do a plug change on
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Old 04-08-2009, 05:14 PM
 
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Okay, I will do that... I ask the autozone ppl to pull the codes again and here it is...

P0171 (and for Honda it means either large vacuum leak, fuel system concern, ignition system concern, MAF sensor faulty, or HO2S/AF ratio sensor fault)...

There is also one more code... its P0170 but there is no "Honda" troubleshooting for it... there is one for Kia and Mazda... Kia says Check other service codes, high or low fuel pressure, leaking fuel injector or regulator, or blocked exhaust or Air intake system...

Is there anything else I should do other than change the fuel filter (is there a type of service for that?) and clean the throttle plate (I am not sure I even know what that means)...
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Old 04-08-2009, 05:44 PM
 
Location: Eastern Washington
8,825 posts, read 23,242,151 times
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OK, I don't have a Honda code book in front of me but the gist of these 2 codes is that the computer is "seeing" an air/fuel mixture that is not only not the correct one it's trying to control to, but "out of bounds" ie the computer is casting doubt on the reliability of the O2 sensor, MAF sensor, etc.

If you want to DIY, I'd start with the fuel filter and then clean the throttle plate. In general you'll find the throttle plate near the inlet of the intake manifold, with a plastic tube going from it over to the MAF (Mass Air Flow) sensor and air filter. You can take the tube off, generally there are a couple of clamps similar to hose clamps holding it on, and then spray cleaner on the throttle plate, you may want to move the throttle lever so as to get the back side of the plate. TP cleaner is similar to carburator cleaner, but a little different formula the guys at Autozone know what it is and out of courtesy I'd get it there since they pulled the codes.

I'd get a factory Honda, Bosch or Purolator fuel filter in preference to Fram. Just personal preference.

Having done the filter and cleaned the throttle plate, if you are in a wrench-bending mood still I'd change the O2 sensor as well.

Or, go to your favorite local indy service shop, tell them what the car has been doing and the codes, that the fuel filter is original, and see what they suggest. Essentially, it's time for a "major tuneup", or at least the most important parts of one.

I'm repeating myself but if the spark plugs have not been changed I'd do that too. Ain't hard, and will provide benefit.

If this car has a belt-driven cam, and I think it does, it's about due to replace that as well.

This car has, probably, served you quite well for several years without anything but gas, tires, and oil from you, it needs a little more to keep going.

I have no idea if the car is worth dumping some money into or not, you have to decide that, but it's time to show it some love or it's not going to stay reliable.
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