tca217 Posted July 26, 2007 Report Share Posted July 26, 2007 Was blasting down the freeway last night (between 75 and 85 mph) and my CEL came on. Got home and pulled codes and got 113 in the A 2. According to my Haynes book it stands for "Short term fuel mixture too weak". Could someone tell me what this means? This is the second time it has happened in the last 2 weeks. Checked for loose or broken vacumn lines, ect. Last time it happened I found the plastic tube going from the air box to the throttle body had a crack in it. I replaced it and cleared the codes and all was well till last night. Checked that same tube again and it is tight and not sucking any thing it is not supposed to. Appreciate any ideas anyone can throw my way. By the way it is a 94 855 N/A auto with 188,xxx miles and runs great. Just did oil and filter and air filter service about a month ago, everything looked great. Thanks for any ideas and help. Link to comment Share on other sites More sharing options...
bagodoosh Posted July 26, 2007 Report Share Posted July 26, 2007 unfortunately with -96 the code doesn't translate to anything i am familiar with.vadis mentions to check O2 sensor and MAF signals at the ECU/MFI pins. Link to comment Share on other sites More sharing options...
AlvinL Posted July 26, 2007 Report Share Posted July 26, 2007 Below is for a 94 with a B5254FS LH 3.2 engine...DTC information MFI 1–1–3ConditionThe short term fuel trim value is a measure of the manner in which the injection period included in the basic MFI module program must be varied to ensure that the engine is supplied with the optimum air/fuel mixture. This optimum mixture corresponds to a value of λ = 1. If the engine is running lean, the short term fuel trim will extend the injection period to restore the optimum mixture. A DTC will be recorded if the engine runs so lean that the short term fuel trim reaches its upper limit and remains there for 166 seconds.Substitute value None.Possible source-HO2S signal lead short–circuited to ground.-HO2S faulty.-Contact resistance and oxidation in MAF sensor connector.-MAF sensor faulty.Fault symptom -Fault may cause high fuel consumption and driving problems. Link to comment Share on other sites More sharing options...
tca217 Posted July 26, 2007 Author Report Share Posted July 26, 2007 Below is for a 94 with a B5254FS LH 3.2 engine...Thanks AlvinL, but can you break it down so a layman can understand? What and where is a HO2S? If the MAF was bad or faulty you say the car would suck a lot of gas and run bad but my car does neither. It is still pulling around 24 to 26 mpg and runs like a top. Drivability is great, doesn't miss a beat, is smooth and very responsive when I smash the gas. When I cleared the codes the CEL didn't come on again till after I made 3 trips from my house in Lakewood to the casinos in the northern part of San Diego County, (about 100 each way). Each time I go down there it is late in the evening and I don't come back till around 3 in the am because that way I can play in the canyons and fly home on the empty frewway at 80 + mph. Seems if the MAF was bad the CEL would come on alot sooner than it has. That is what has me questioning what the heck is going on. Any ideas? Thanks again for the explanation. Link to comment Share on other sites More sharing options...
bagodoosh Posted July 26, 2007 Report Share Posted July 26, 2007 HO2S = heated O2 sensor. it should be located before the catalyst converter.the way the car works is that it measures the incoming air via MAF sensor. it then tries to mix appropriate amount of fuel to achieve whatever air/fuel ratio. it monitors this ratio under cruising condition via the O2 sensor - this is called closed-loop.your case sounds like what volvo defined as P0172 in its OBD2 models.it thinks the car is running lean (too much air). this can be caused by low MAF or O2 reading. if your MAF is reading low, then the computer's initial "guess" for the fuel mixture will also be low. this results in a correction to add fuel; if this correction is consistently 25% over, computer gives up and triggers the CEL with that code.if the O2 sensor is dead or faulty and giving a low voltage reading, the computer will also see this as a lean condition.my guess is either some of the measured air is escaping (after MAF, before the cylinders) or that your O2 sensor needs replacing. the question is whether your car is actually running lean or just that the computer thinks so and is dumping a lot of fuel to compensate. you can take out your spark plugs and check whether they are fouled (black).how many miles does the car have? it could just be time to replace the O2 sensor.EDIT> a couple things to note:during spirited driving (throttle pressed in more than 65% or whatever it is) the O2 sensor is bypassed. this is refered to as open-loop. if you reset the ECU and drive the car hard, it'll just take longer for it to set such codes. the monitoring only happens during warm idle and cruising at partial throttle.also, these codes take a while to set. sometimes people think when the CEL comes on, it relates to the conditions in the instant the lite comes on. in this case you can see it'll take 166 seconds for the code to set. aside from that, it may take quite a bit of driving before "trip" conditions are set and for the computer to trust the sensor signals. Link to comment Share on other sites More sharing options...
tca217 Posted July 28, 2007 Author Report Share Posted July 28, 2007 Thanks for that explanation. I bought the car with about 175,000 miles on it and now has about 188,000 on it and I know that I have not changed the O2 sensor and there is no way of knowing when or if it has been changed so I think I will change it anyhow for piece of mind. Didn't know about the bypassing with the 65% or more throttle but that makes alot of sense. Thanks again for the help and the explanation. Link to comment Share on other sites More sharing options...
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