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Discussion Starter · #1 ·
I had this same code on my last ZX2. On that car it turned out to be the hose coming off/breaking off from where it attached to the nipple on the intake manifold.

The mechanic that I took it to did not figure it out but when it was sitting outside in the lot I saw it and told him. But since he failed to diagnose it I took it to another mechanic who simply clamped another hose on there and then everything worked fine.

The PCV hose on my current ZX2 had issues as well where it attached to the PCV valve. I used a small section of hose to do a repair there but I now worry that the hose may be blocked off as I just changed the air filter and saw some oil on the old filter, indicating that there is too much crankcase pressure so it is pushing some oil into the intake.

I am not sure if that hose is even available. It seemed like maybe there is a Dorman hose available at Auto Zone that might work. I will call them tomorrow. But I also don't know if that has anything to do with the P0171 code. I am going to take a closer look at it tomorrow. On the old car it was pretty obvious that there was an issue where that hose attached to the intake manifold.

The car may have to go into the shop so that they can look at the fuel trim numbers in real time and figure out what is going on. The crazy thing is that when I got this car it had a few bad vacuum lines but I fixed those (they were on that valve behind the motor on the firewall, passenger side). However, it was not throwing any codes despite having those bad vacuum lines. On my first ZX2, those same bad lines did throw a P0171 code. Now I can't seem to see any bad vacuum hoses but it is throwing that code. Idle seems to be really rough right now as well, which I understand can be another indication of a vacuum leak.
 

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Discussion Starter · #2 ·
I just saw and commented on another thread on here asking about that very same PCV valve hose. I might call the local dealer to see it they have that since I now have the part number. But it is also available on Ebay. Tomorrow I will also take a better look at that hose to see if it might be kinked and blocked off. But I have my doubts as to whether a blocked hose would contribute to the lean code. It could definitely contribute to the oil in the air filter but unless that hose is the cause of a vacuum leak, I doubt it is contributing to the lean code. On my old ZX2 it was the cause for the lean code.
 

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Instead of throwing parts at a problem, I always recommend diagnosing the problem yourself. If you spend that money on a scanner (the best way to do this is an inexpensive ELM327 OBD2 adapter and the free but powerful ForScan software for PC) that can do live data simply looking at how the short term and long term fuel trims behave under different conditions can give you direction on what is causing the lean code.


Here is a video specifically on a ZX2 that I vaguely remember fixes a broken/cracked/missing hose (though that may have been a different video), but the PROCESS of how he comes to that conclusion is the important takeaway, he even explains in depth the general process of diagnosing a problem based off of evidence and not symptoms at the beginning of the video.
 

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Discussion Starter · #4 ·
Thanks. Yeah, I watched a few videos last night and got a good idea of why it would throw that code. Obviously vacuum leaks are number 1, but that could be a lot of things. I might try spraying around to see if I can locate it. I will also watch those two videos. Either way that crankcase ventilation hose is going to get replaced since it is bad.
 

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ELM327 adapters are very cheap, if you have a laptop you can get ForScan for free which will probably be able to read and do more on Fords (and some Mazdas) than most scanners, even ones that cost hundreds of dollars. They will be able to read more points of live data than basic scanners that have obd2 data. If you have a laptop that supports bluetooth you can even get a bluetooth ELM327 adapter that will work with your phone and the laptop.

A vacuum leak can cause a p0171 code, but fuel trims will improve when RPMs are raised because once you open the throttle the engine is no longer producing very much vacuum. Vacuum leaks are the most common cause and any old car is effectively guaranteed to have a vacuum leak just due to how many things can cause them including aging vacuum lines. There could be more than JUST a vacuum leak, which is why it's important to "prove" you've fixed the problem by checking the fuel trim data after making a repair. Typically a positive fuel trim of 20% or more will cause a p0171, but you could have a 19% positive fuel trim after fixing a small vacuum leak, reset codes, and believe you've fixed the problem because the fuel trims are no longer high enough to set a code.

As for looking at the data to see if it has a vacuum leak, raising RPMs with a vacuum leak we would expect to see the short term (and/or the long term) fuel trims improve (closer to 0) where the engine is closer to adding as much fuel as it would expect that it needs to based off of MAF/RPM/Throttle position, etc, etc. It will then use o2 sensor data to make adjustments to the fuel trim if the car is running rich or lean.
 

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Discussion Starter · #7 ·
Those were good videos. I just finished watching them. Since I don't have any access to a laptop or ELM327 adapters at this time I will most likely start with simply trying to see if I can detect any vac leaks since that can be done quite easily. I have heard a couple ways of doing that. One is spraying around with carb cleaner and looking for any change. Another was spraying around with water. And finally he used propane, which I like. Also there is a visual inspection.

I'm just going to start there and then maybe it will go in for service if I can find the right mechanic to do the diagnosis. I understood everything that he was talking about.

I will report back if I find anything.

On my old car I had gotten a P0171 when two things happened. The first was a small vac line on that canister on the firewall. I don't remember what they call that. Fixed all of the vac lines in that vicinity and then the second one was when the crankcase vantilation hose broke off of the intake. I had a mechanic fix that and then never saw the P0171 again.

I am definitely going to go talk to my mechanic. I have not been to him in a while but he does good work. So I will go have a discussion with him about fuel trim. I am sure he has the proper equipment to take a look and diagnose. But of course, I would like to have as much information as possible before I hand the car over to a professional.
 

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typically 0171 codes are caused by the plastic/rubber hose that runs from the pvc baffel to the intake on the back side of the manifold.. look for any broken or cracked vacuum lines, intake tubing. any source for extra air
 

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Discussion Starter · #9 ·
typically 0171 codes are caused by the plastic/rubber hose that runs from the pvc baffel to the intake on the back side of the manifold.. look for any broken or cracked vacuum lines, intake tubing. any source for extra air
I just ordered the proper Ford PCV hose yesterday. It will be here next week and then I will probably take the car in, have them do that and look for any leaks. They can replace the PCV while they are at it. In the meantime I will continue to do a visual inspection and also see if I can get my hands on a small canister of propane in order to see if getting that close to any of the hoses or connections makes a difference in the idle.

The code set every time at idle. Twice when I ran the car hard and then went back to idle, which makes sense because then the vaccum is at a maximum.
 

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Any of them do ABS and SRS and Battery/Oil/TPMS reset, and live data on everything (including ABS wheel sensors) and bi-directional testing and key fob programming?
My experience is limited to two F-150s (2004, 2007) and my 98 zx2, and I have only used one adapter. I believe the ELM327 adapter doesn't matter as long as it will work with ForScan. ForScan will do just about everything, but for certain things requires you to purchase the full software, this is mostly limited to certain programming features like programming new keys.

I have read ABS codes on the F-150(s) as well as SRS codes on the zx2, but have never tried to do anything beyond that as far as ABS/SRS. I have done bidirectional control on the zx2. Pretty sure forscan will do an ABS bleed like how the dealer would do it.

Usually fobs can be programmed without a scan tool, right?
 

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Discussion Starter · #12 ·
Funny thing about that video that was posted is that the guy went on and on for about 45 minutes and finally when he figured out the issue, it was a massive vacuum leak because of a split hose that had come disconnected. LOL. A quick visual inspection would have found that problem. He also used a thing of propane.

I did go look up some ELM327 adapters on Ebay, but interestingly wnough there was a note on the ForScan page claiming that some of them might not work correctly, that they were "bad clones"...

Important note: almost all of adapters sold under "ELM327" label are "clones" (use not original ELM327 chip). In past few years 80% of them are "bad" clones, and unfortunately this ratio grows. "Bad" clones are not fully compatible with original ELM327 and will not work with FORScan. FORScan uses service level protocols and requires adapters that are fully compatible with original ELM327. Other software that uses standard OBDII protocol usually work with these adapters, so people usually don't understand the problem. The problem is that service protocols are more complex than regular OBDII ones and this is why it is physically impossible to make FORScan work using these devices. We recommend to obtain either original white-label adapters listed above (Scantool OBDLink, Vgate vLinker, ELS27 etc).
Important note 2: after many years of continued project development, even the "good" ELM327 ceased to meet all of FORScan requirements. Thus we do not recommend any ELM327 anymore. FORScan will continue to support ELM327 adapters, but some new functionality may be limited or refuse to work on outdated adapters.

I also found this thing on Ebay for about $40...

Font Screenshot Technology Software Cameras & optics

Says that it is compatible with all cars 1996 and newer...
 

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Funny thing about that video that was posted is that the guy went on and on for about 45 minutes and finally when he figured out the issue, it was a massive vacuum leak because of a split hose that had come disconnected. LOL. A quick visual inspection would have found that problem. He also used a thing of propane.
You would be amazed how many times someone claims "quick visual inspection" or "throwing parts would have been faster" on his videos. Just because that was the issue here, doesn't guarantee every time someone has a p0171 code that they have a vacuum leak, let alone in that one spot just because it is a common problem.

The point is the process by which he came to the conclusion, with multiple methods and proved it was the only issue, not one of potentially many issues. Like I said, I believe he had another video on a Focus zetec where it was an entirely different issue with similar symptoms/codes.

Good point on the ELM327 adapters.
 

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On the FORScan site they list some adapters that work. They are right about the clone adapters though. The first one I got only worked on CAN bus vehicles, it took it apart and it didn't have an ELM327 chip in it, just a CAN bus interface chip. Then I bought the BAFX bluetooth adapter that is recommend everywhere and it's worked with every vehicle and software I've thrown at it.
 
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I have the free version of ForScan and an ELM327 adapter (the one with the switch for Fords), and so far I've only used it to do the battery reset when replacing the battery on a 2011 Ford Edge. Yeah, if all the vehicles I had to maintain were Fords, it would be a no-brainer to just get the paid version of ForScan and put it on a better laptop (I use Linux, but can get ForScan to work on that). But I maintain 4 vehicles and that's the only Ford. I also maintain an Oldsmobile, Dodge, and Toyota (all of these are 1999-2000 model year vehicles). Just worked out that way due to inheriting vehicles, and at my and my GF's age, we might not ever buy another vehicle. I already have a relatively nice handheld scanner (good for it's day, it's probably 10 years old). Does emissions stuff well on all vehicles and live data / freeze frame, but very limited ABS/SRS stuff. It can't do things that would be nice like read ABS wheel sensor data and bi-directional stuff. The ForScan solution only works on one of the vehicles. I know that there is TechStream for Toyota that's like a ForScan equivalent, but I have never needed it, even though the 2000 Camry I maintain does have 167K miles on it.
 

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Discussion Starter · #16 ·
You would be amazed how many times someone claims "quick visual inspection" or "throwing parts would have been faster" on his videos. Just because that was the issue here, doesn't guarantee every time someone has a p0171 code that they have a vacuum leak, let alone in that one spot just because it is a common problem.

The point is the process by which he came to the conclusion, with multiple methods and proved it was the only issue, not one of potentially many issues. Like I said, I believe he had another video on a Focus zetec where it was an entirely different issue with similar symptoms/codes.

Good point on the ELM327 adapters.
I get it. He was trying to make a video of how getting live data can find an issue. But if he would have just bothered to look first he would have quickly found that issue because it was a hose that was not even attached. Just saying... I know that will not always be the case. I did watch a bunch of videos on YouTube looking into how to diagnose various "lean code" issues. I learned a lot.

My car right now has the service light turned off and it is not coming back on. The last time I got it to come on was when I ran the car hard and then went back to idle. That actually happened at least two times. Right now it has been over 400 miles since I last reset the light and I have changed my driving habits to make it less likely that it will come back on again. That does not mean that there is no issue, but it does indicate that the issue is not a severe one that would need immediate attention. When I go in to my mechanic to get that PCV hose replaced I will have them take a look at it. Then maybe they can plug it in and tell me how the fuel trim numbers look.

I do like the look of that $40 scan tool for sale on Ebay. I might just get one so that I can play around a bit and learn. Would be good to have anyway.
 

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The PCV hose is actually a plastic tube with rubber elbows (behind the engine on the bottom of the intake manifold & at the PCV valve. These elbows are the #1 cause of zetec vacuum leaks, and the elbows can be purchased cheap at the local parts store. The #2 cause of zetec vacuum leaks is the valve cover gaskets, but I would check/replace all vacuum hoses before messing with the valve cover.

Let us know how it turns out, and BTW the Bluetooth OBDII readers can be had for $12 on eBay. You download free OBDII apps on your phone to read the live data.
 

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Discussion Starter · #19 ·
The PCV hose is actually a plastic tube with rubber elbows (behind the engine on the bottom of the intake manifold & at the PCV valve. These elbows are the #1 cause of zetec vacuum leaks, and the elbows can be purchased cheap at the local parts store. The #2 cause of zetec vacuum leaks is the valve cover gaskets, but I would check/replace all vacuum hoses before messing with the valve cover.

Let us know how it turns out, and BTW the Bluetooth OBDII readers can be had for $12 on eBay. You download free OBDII apps on your phone to read the live data.
Yeah, I only used a small section of hose that fit to try to do a quick repair on that PCV valve hose. But that could lead to a kink. I could not find any elbows that would work when I went to O'Reillys. So I already have the correct replacement Ford hose and it will go on soon. Also valve cover gasket is going to get replaced soon, along with new spark plugs. I usually do those both at the same time.

This car is going to require some work if I am going to high mileage it. No doubt about that. Going through the front suspension right now. Then timing belt. Then engine mounts. I don't know if I trust the mileage on the odometer or not. It said 133K when I got it and now it says 183K. The car runs very well right now. The engines are durable and reliable if taken care of properly. Simple little cars.

My last ZX2 made it to 326K before I took it to the junkyard. It could have gone longer but then the money put into it to do that could not be justified. I can vouch for 200K of those miles myself. I can not verify if the 326K number is accurate or not because when I got that car the odometer said 189K or something like hat and I switched in a cluster that said only 122K. So I immediately "took off" over 60K of miles. But I also could not tell if the cluster that I took out was original or not. So who knows how many miles it actually had on it. It got T-boned and totaled when it had around 233K miles on it and then I ran it almost another 100K miles...
 

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Discussion Starter · #20 ·
Well, the car is going in for service on Monday. So far I have put 50,000 miles on this car and now some of the issues are starting to appear. At least this time around I have a better idea of what is going on. With my old ZX2, I had no idea that there was in fact a separate breather valve and PCV valve. So I never changed out the PCV valve, not once. Probably why the valve cover gasket was leaking so bad...

On Monday the mechanic is going to replace the PCV valve hose (I have the proper Ford one), the PCV valve and the grommet that the valve sits in. Also do both ball joints. I usually do ball joints myself but I got stuck on one when the nut would not release and started to round. So I said "screw it" and will take it in to get done. The PCV valve is either clogged or the small section of hose that I used to try and effect a repair on the hose is kinked. Either way there are signs that oil is going where it should not. When I replaced the air filter it had oil on it where the hose from the breather valve goes into the intake. Also I just pulled a spark plug wire to see the plugs swimming in some oil. All of these things are going to get addressed once the PCV system is correct and functioning again.

Timing belt is due to get replaced in just over 5,000 miles. Will get a new water pump then as well. After that engine mounts will get attention and then valve cover gasket and new plugs. Then it's off to over 200,000 miles and beyond.

The PCV valve situation may be the cause of that lean code popping up after running the car hard. I ran it a bit hard the other day and the code came on. It had been a while since I last saw it. Also a bad PCV system can cause a rough idle, which is definitely happening. Just trying to knock down one issue at a time.
 
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