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Vans & Minivans Ford Windstar Ford Windstar - fixing PO171 and PO174
21 messages, Last post on Jul 04, 2009 at 10:18 AM
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Replying to: dmdkana (Mar 26, 2008 4:21 pm) The conditions under which it is lean can be used to steer the diagnostic direction. When those codes set, there was also some "freeze frame" data that went with one of them. Now, maybe the tool being used won't show it to you, depending on the quality of the tool. But that FF data is helpful. A lean condition at idle only, and not higher RPMs is a possible indication of a vacuum leak. A lean condition at higher RPMs but not at idle is an indication of a fuel delivery problem like pump and filter. A lean condition at idle that suddenly swings to a rich condition at higher RPMs is an indication of a contaminated MAF sensor. However, it it extremely common for the plastic upper intake seals to leak vacuum. It is also very common for the IMRC shaft seals in the lower intake to leak vacuum. The upper seals aren't that big of a deal, but the IMRC shaft seals in the lower require a complete new lower intake manifold (the actual aluminum manifold) to correct. Ford also has a reprogramming (reflash) that helps. Often, a new set of upper seals plus the reflash will "hide" the IMRC shaft seal leakage. But eventually the lower manifold gets do worn out that the reflash won't hide it and you'll need a new lower intake manifold. That is just one common issue may not be your problem. You will need to take the vehicle to a shop that can monitor fuel trim PIDs on the scan tool. They can spray the intake seals and watch the reaction in the trim PIDs to determine any vacuum leak. Another common issue is when someone replaces the air filter, and the plastic PCV hose pulls out of the snorkel on the back side (nearest the master cylinder)... that causes a lean code at idle due to unmetered air entering the engine. I'd check that PCV hose first and if that is ok, take it to a shop. Also, the PCV hose that goes to the PCV valve (in front).... make sure oil hasn't gotten to the rubber part where it slides onto the intake, swollen it and causing it to leak vacuum. Those are a couple of DIY'r repairs I can think of... the rest really need a tech with proper test equipment to figure out.
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Replying to: dmdkana (Mar 26, 2008 4:21 pm) |
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hopefully autodr or anyone with great knowledge can assist. i have a 2003 with 43,000 miles, and the problem im having is high idle but no error codes and i cannot find leak. When I start cold, it runs 1600-1900 rpm initially, and then drops to 900 like its supposed to, but will only stay there a few seconds, then it'll ramp up to 1100 or so. At this point, if I put it in drive, it'll take off on its own with touching the pedal, and the rpms will slowly rise including the vehicles speed, and will get to 20mph sometimes. Any driving during this period before its fully warm (which takes 15 minutes) and its as if it'll coast forever, and I'm using the brake instead of the accelerator. It seems like its 200 to 300 rpm higher than it should be. When the engine is fully warm, at a stop it'll be at 800rpm, but if I put into neutral at this point, it'll come up to 950rpm. Its driveable, however, its very annoying and is not pleasant driving short trips. Ive replaced the IAC valve, throttle sensor, cleaned MAF, throttle body, cable, and tried to find any leak but am coming up short. Note that I am not getting any error codes, stored or unstored. Please assist. |
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Replying to: diclemeg (May 01, 2008 5:28 pm) What kind of vehicle? I'm assuming something in the Ford line.
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Replying to: autodr (May 01, 2008 6:42 pm) |
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I finally attached a scan tool.. .... and here is what i found..... .the "absolute throttle position" reads at 18.4% without touching the pedal, and goes up from 18.4 if I do touch the pedal. If I disconnect it, it reads 0%. The short and long fuel trims were -1% and 3% and varied but never got above 6%... recall that i already changed the TPS sensor a week ago. calling all experts, please advise here.
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Replying to: diclemeg (May 04, 2008 5:16 pm) If your scanner won't give you the voltage, use a DVOM directly at the sensor and measure voltage on he signal wire and the ground. There should be no voltage on the ground wire. TPS voltage should be around .8 If the signal voltage is higher than that with no voltage on the ground, inspect the throttle plate stop screw... maybe someone adjusted it up. If not, then suspect the wrong TPS or a poorly made one. If the voltage is correct with the absolute TPS value reading that high, disconnect the battery... reconnect after a minute, and see if the absolute TPS is now correct at zero. If it is, test the battery,
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Replying to: autodr (May 04, 2008 6:36 pm) the scan tool does not have volts. however, get this.. when the tps sensor is attached to the throttle housing, it actually has to open and turn a little bit, which is causing the 18.4% reading. i know this because i took it off with the computer in front of me and it went to zero. then i put it on half way and it read zero and in order to seat the screws, i had to turn it to the point that it read the 18%. The flat plastic knob that is attached to the throttle plate and what turns the tps sensor at closed position is not at 0 degrees like this " -- " but titled downward like this " \ " (but not that exagerrated). I guess the question is whether the pcm knows that the downward tilt is absolute zero and accounts for it. |
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Absolute throttle position is NOT a measured position. It is a learned or calculated position. It is the position that is in reference to the lowest measured TPS voltage. You need to know the measured voltage. That phantom 18% may be coming from an incorrectly learned closed TPS position. If you have a volt meter, try measuring the vltage at the TPS and let me know what you read. There are 3 wires there, One is a 5 volt reference, one is a a ground which will only have a couple millivolts on it... and the other is your signal wire. It will start around .8 volts closed and raise up to about 4.8 at wide open throttle. You have only generic level scan access then.... which is better than nothing at all. But, you have to remember that you are not seeing "actual" TPS position on that scanner... you are seeing more of a "virtual" TPS position. The position displayed is relative to the lowest measured voltage that the PCM saw. You can also try disconnecting the battery for several minutes then reconnect. That will clear out the lowest measured TPS voltage from the PCM's memory. And unless the TPS is at a ridiculous high level... like more than a volt, it should accept that first key-on TPS voltage as the new "closed" TPS voltage. It may be that the TPS they gave you is the wrong one. I'm assuming you went to a part's store rather than the dealer, which doomed you to get the wrong one early on. At the part's store, they ask you year. make, model, and engine and hand you the only one they list for it because they do a "one size fits most" thing. Whereas there may be 2 or 3 different ones for that vehicle depending on the vehicle's calibration code which the dealer will use to get the correct one. However, some TPS's are under slight tension when installed so that test you gave may or may not prove anything. I really would like the voltage to get a better idea of where that TPS is sitting at at closed throttle position. Another quick test here would be to unplug the IAC valve. If the engine idles down to the point of near stall, or does stall, then it is likely that the phantom TPS position is the only problem. When the PCM sees the TPS open, it cranks the IAC open to anticipate "dashpot" mode when you let off of the gas. |
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I have three MIL codes , 2 lean banks and a EGR flow code . I replaced the EGR and EGR flow sensor . Then , I found that the linkages to both IMRC 's had fallen off . I need to know 2 things , 1) does anyone know where to get the linkages and retainers besides from Ford and ,2) could this be throwing lean codes ? I am assuming that the rough idle is associated with the IMRC being inop . It acts sort of like a vacuum leak but I cannot find one and that is what is leading my this way . Help and thank you.
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