Engine Trouble Codes!

Discussion in '1994 - 1995 Specific Tech' started by joetrainer31, May 28, 2014.


  1. joetrainer31

    joetrainer31 Member

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    I could certainly use some help from someone more car savvy than I am. Recently, my car has begun to hiccup while driving and the idle has become less stable (i.e., not surging, but more like small skipping up & down). Furthermore, I went to the store and my idle stuck at 2500 rpm not matter what I did. Needless to say I burned the clutch a little getting it home.

    I do have an SCT 4 bank chip that I recently installed. It ran great for the first coupe of weeks before the above symptoms started. The symptoms are more pronounced on a tune setting and less pronounced on the stock setting.

    I called Bama and they said that it could very well be the old TPS and IAC going out because the chip "demands more of electronics." That seemed at least probable to me. Therefore, I replaced the TPS (Ford TB non adjustable) and IAC with new BWD components.

    I did not check codes before, but the CEL did come on when the idle hung up, before changing the TPS and IAC. I have checked codes now and I get 121 KOEO, and 121/411 KOER. I'm stumped. What am I missing?
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  2. joetrainer31

    joetrainer31 Member

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    Anyone have an idea?
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  3. toyman

    toyman SN Certified Technician

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    With KOEO check the TPS signal voltage using the TPS ground not the engine. Closed, the voltage should be close to 1v. There are 3 wires. Voltage reference, ground and voltage signal to the ECU. The 121 code would indicate that is not what you are going to see. 411 is likely related. Let us know what you get and we can go from there.
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  4. joetrainer31

    joetrainer31 Member

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    Thanks, Toyman. I've been really sick and unable to get to the car. However, I'll follow your advice exactly and get back to you ASAP. Can you remind me of the wires' color/function? I cannot remember which is which. Thanks again!
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  5. toyman

    toyman SN Certified Technician

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    At the connector the two outside pins are ground and reference. The middle pin is the signal. Don't recall the colors but ground is probably black. From the above you should be able to determine the ground as you want the voltage measurements using the sensor ground NOT the engine.
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  6. joetrainer31

    joetrainer31 Member

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    Right. I'm going to try and check the voltage today. When I put the new sensor on, I had to manipulate it a little because it did not fit the exact position the old sensor had left off at. I'm thinking that may be the issue.

    However, since the sensor is non-adjustable w/an FRPP TB I'm thinking that I'll need to take the entire sensor off again and try to rotate it by hand again, and again, and again until I happen to get it into the same position the old sensor left off at. Does that make sense?
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  7. joetrainer31

    joetrainer31 Member

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    Ok, so I took the car to the local shop because i've been too sick to deal with it. That was a mistake. I think in some instances it might be better to let the car sit.

    Anyhow, I took them the car, gave them the codes, and let them know that the TPS & IAC were just installed. Later that day they called me and told me that the problem was the EGR solenoid. I asked them how that addressed the codes I had. They said that it was the underlying cause. I had a hard time seeing it that way but I let them "fix" it.

    Anyhow, the car had the same symptoms. So, today I decided to pull the SCT chip to see if that was a problem. It was not, but now it is out of the equation. I noticed that when I got the car back that the idle was too high (950-1000). So, I did a base idle reset. The idle is now about 700 w/IAC plugged in. Although the idle still jumps a bit.

    My KOEO/KOER tests produced the same codes (121 KOEO/121 411 KOER). So, I'm going to drag my sick bahind out to the car and test the TPS like I wanted them to do in the 1st place. I'll use the TPS ground as instructed. I'm confused about the other wires. Would the volt meter's red wire go to the TPS signal, or 5v wire?
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  8. toyman

    toyman SN Certified Technician

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    Yes. First check the reference voltage. You want to see 5v on the meter. Next check the signal voltage. KOEO it should be about 1v moving smoothly to about 4.7+v WOT. Installing the TPS is straight forward. It will only install on way. FWIW my FRPP TB has an adjusting ring for the TB. However, it tested fine without any adjustment. I suspect someone may have messed with the throttle adjustment screw (threaded rod on an SN). May not matter depending on the closed voltage reading.
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  9. joetrainer31

    joetrainer31 Member

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    Ok, so the TPS signal = reference voltage, and signal voltage = 5v wire?

    Yes, I saw that my 65mm FRPP TB only allowed for me to install the sensor one way. When I went to install the sensor it did not line up to the same position as the old one (i.e., the tongue & groove did not match up so that the screws could be replaced). Therefore, I manipulated the TPS & TB side by slightly turning it (i.e. the sensor) in order to get the screws to line up. I'm wondering if that is my problem.

    Nonetheless, I want to make sure that I am understanding you wire descriptions and order of testing steps correctly. Please double check my understanding above and correct if necessary. Thank you!
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  10. joetrainer31

    joetrainer31 Member

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    So my TPS voltage was 1.36 at the lowest I could get it. That's 36% out of tolerance. I took the part back to the store, but did not get a new one because, get ready for it...Ford thought it necessary to have two different parts for a 95 GT TPS.

    There is an F15F-AA, and there is an F2SF-CA. According to my research the two parts are not interchangeable because they are calibrated to a specific ECU. The most difficult one to find is the one I have (F2SF-CA). It has not been manufactured for years. Auto part stores seem to be incapable of distinguishing the difference so as to provide the correct part. On the Ford parts website the F1SF-AA (CX1406) is listed at $108, and the F2SF-CA (CX1488) is listed at $67. Although, the parts guy just told me that he cannot get either part for me.

    I'm quite stuck.
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  11. toyman

    toyman SN Certified Technician

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    You may not be stuck quite yet. If the throttle adjusting rod/screw was messed with some time in the past in an attempt to change the TPS voltage. With the volt meter connected you can try backing off the rod/screw to bring the TPS signal into range. The caution here is when you back off on the setting ensure the throttle blade doesn't bind in the TB when you're done.
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  12. joetrainer31

    joetrainer31 Member

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    Ok, great advice. I'll certainly keep it in mind.

    I'll keep it in mind because, after nearly 4 hours of searching, I found that the particular TPS I'm looking for (F2SF-CA) underwent several part number changes through its history. I found a website that gave me a list of interchange numbers for the Ford part here (http://www.yoyoparts.com/oem/11745221/standardmotorproducts-th156.html).

    After I found the site I searched and cross referenced just about every part number they listed. Most places across the country didn't even make the aftermarket part, but I ended up back at the 1st place I tried; fordparts.com!

    I have an account with that site and my local dealer. The problem was that when a parts guy hears what car you have he automatically thinks the part is unavailable and will not cross reference for you!

    The part number that will properly replace F2SF-CA or CB is CX1495. To be fair the fordparts website did not even show that part as an option for my car. They showed CX1406 which is for F15F-AA, and CX 1488, but not CX1495. I had to type the part # into the search box.

    So, I got the part from the dealer that said it doesn't exist anymore. I just needed to research it myself and follow its numbering history. Oddly enough, all the specific replacement parts for the F2SF-CA (e.g., Standard, AC Delco, BWD) were not available anymore! They still advertised them, but they were unavailable.

    When the Motorcraft part arrives I'll install it and check the voltage as you advised. If it is still off then I'll refer back to this thread for the fine adjustments. Also, I went ahead and bought a Motorcraft IAC (CX1842) to use w/the TPS. I don't want any trouble and it seems that Motorcraft parts of this nature offer the least amount of it.

    Thanks again!
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  13. joetrainer31

    joetrainer31 Member

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    Toyman, as I reread your post about fine tuning the TPS via its adjusting rod/screw I had two questions:

    1) Are you referring to the screw on the left side of the TB by the throttle cable, or the allen head adjustment on the right side, or both?

    2) If the blade binds I assum that one could feel the bind in the throttle linkage via resistence to hands on manipulation, yes?
    #13
  14. toyman

    toyman SN Certified Technician

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    Not so much as fine tuning but rather to bring the idle voltage signal back into spec. The spec range is from .65v to 1.25v. It is within this range that the ECU recognizes the signal as being at idle.

    The one by the cable on the left side. The allenhead screw is the IAC bleed valve is only adjusted to literally fine tune the idle.

    Yes. If the throttle blade is completely closed it may bind. You should be able to tell by manually opening the throttle.
    #14
  15. joetrainer31

    joetrainer31 Member

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    Toyman, thank you for all your help. I will certainly refer back to this blog when I get my part.

    So, the Ford dealer emailed me back indicating that my order was canceled! I called and inquired as to why it was canceled. After being probed they admitted that their inventory was off so they could not sell me the part. They also said that it is obsolete and does not exist.

    Therefore, I started researching more and found the part at Star Ford/Lincoln in Glendale, CA. They said they had 4 of them. I asked the parts guy if he could set physical eyes on the part in order to verify his inventory. He did so, but could only verify 2 of the part in house. However, he did say that 2 more were in his warehouse. Whether or not that is accurate, I do not know. I quickly snatched up both sensors @ $67 each.

    Finding the exact sensor I needed has been a real pain. I've researched countless sources and read countless blogs like this one. So, if anyone in the future runs across the same problem I hope this information is helpful. In order to be as helpful as possible I'm going to do 2 things. The first thing is to list this particular part's supersession of numbers. Sometimes its hard to locate a part if you do not know its number history, and sometimes vendors only have antiquated part numbers!

    The history is as follows: original # on physical TPS is F2SF9B989CA. This was later changed to F2SZ9B989CB, then changed again to F2SZ9B989C. The older corresponding Motorcraft part number was CX1495. That older number was superseded by DY976. TheDY976 Motorcraft parts as well as their aftermarket counterparts have been discontinued. They are obsolete. Therefore, one must be able to find a left of pile of them somewhere (i.e., a Ford dealer).

    The second thing I and a friend are going to do is test each TPS sensor (i.e., the Ford original I suspect is bad due to trouble codes 121/411, the failed BWD aftermarket, and the new Motorcraft DY976). We will bench test each of the sensor's voltage ranges at 0% throttle, 50% throttle, and 100% throttle in order to observe any differences and to gain an understanding of a proper operating voltage range for TPS model F2SF9B989CA (DY976).

    If we can determine the proper voltage range on a brand new sensor then I will display it here so that we will all know the proper operational voltage range needed for a replacement sensor regardless of part number (it is my theory that different TPS sensors, even if for the same vehicle, have different operational voltage ranges). This way, people in the future can simply test a sensor's voltage range regardless of manufacturer or variance of part number and determine if it will function in place of their original F2SF9B989CA.

    Results forthcoming...
    Last edited: Jun 12, 2014
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  16. toyman

    toyman SN Certified Technician

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    The TPS is only a rheostat. They work from the 5v reference. They will all be the same as all the vehicles and sensors use the 5v reference. The important point is to ensure the voltage increase from 1v - 5 (actual more like 4.7) is a smooth linear progression without any fluctuation caused by a dead spot. Don't fry the ones you get by applying 12v.
    #16
  17. joetrainer31

    joetrainer31 Member

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    Ok. I'm only going to use a digital volt meter to check for the results. I've tested two sensors already, the original from my car, and the BWD one from the store, there is a difference between them (about 35%) mostly at zero throttle. Do you think there is any potential harm for the potentiometer using this test method?
    #17
  18. joetrainer31

    joetrainer31 Member

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    UPDATE: I took a 20 mile one way trip out to the Ford dealer. If you live in SoCal you know how challenging that can be. I got there and behold! The 2 TPS sensors were the wrong parts! They did not look mechanically the same and their latest part number (F4SZ(B989AA/DY967) was not related to my original part number (F2SF9B989CA/DY976).

    While there I brought the discrepancy to their attention. They told me that DY967 was simply the latest number for the part I was desiring. I mentioned to them that it looked like a TPS for a 3.8v6 or a 4.6. He stated that it was indeed for a 5.0. I then showed him the history of part number changes that I brought with me, and that his number was no where in that history. He told me that it is because it was the latest iteration. He assured me that the part would fit and be just fine. I told him that I hoped so because it was a long drive.

    I get home, test the part's resistance on the digital mutimeter and it was WAY off from my other TPS sensors. It was double to triple at dead zero on the sensor. Besides the physical fit being questionable, the resistance told me that this sensor was for another car, not a 94-95 Mustang GT.

    Thus, I called the guy back and told him. He said, wait for it, "oh yeah. I did some researching when you left and the sensor is for a 3.8v6." Wait. What?! Yep, just because someone is behind the counter at the dealer does not mean that they know what they are talking about. Also, just because someone's computer says something fits, it does not make it accurate.

    Next time, I'm trusting my own research. Back to square one. I'm going to retest my original sensor in order to observe whether or not it's resistance is smooth throughout its mechanical range of motion. If it is, then I'm putting it back on the car, installing a new motorcraft IAC, doing a base idle reset, and retesting for codes. If the codes appear again and/or if the same symptoms manifest, I'm looking somewhere besides the sensor. To my knowledge there is no complex circuitry inside the sensor, just an arm that swings across some resistive material. Therefore, if the resistance reads as a steady increase on the multimeter as I manipulate the sensor arm then, the sensor should be in normal operating order. Someone please feel free to correct me if I'm wrong. If my thinking is wrong then please do me and future readers a favor and explain [why] its wrong. Till next update...
    #18
  19. joetrainer31

    joetrainer31 Member

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    Update & Resolution: I replaced the TPS with a [very] hard to find exact aftermarket replacement TPS. The part I found (new on eBay) was an AirTex 5S5137. It was about $58. This part immediately resolved the 121 code.

    Next, I had the 411 code (cannot control low speed idle). I assumed that my IAC could be the issue since it seemed to be an original part (19yrs old). I cleaned the carbon out of it last year, but did not want to mess around with a possible limp part. Therefore, I got a Motorcraft unit (CX-1842). I do not like getting these kinds of parts aftermarket unless I have no other options. I installed the new IAC.

    While I was in the area I wanted to make sure that my TB blade was clean so I began to remove the hose from the TB. I saw that the hose was loose! The screw was not even hand tight. I suspect foul play from the local mechanic who had touched the car prior. Yes, I know, local mechanics are not who you want touching your car, but I've been really sick and had no choice at the time. Needless to say, this loose air hose caused a vacuum leak and could easily produce a 411 code as well as my idle problems.

    I also replaced the fluid temp sensor w/a Motorcraft unit (DY-681), installed a K&N filter, and am replacing the VSS (Motorcraft DY-588) on the side of the gear box for good measure.

    Lastly, I decided to do a base idle reset the proper way. As I began the procedure I found that someone (local mechanic?) had been messing with the idle adjustments on both sides (i.e., throttle stop & air bleed). The settings were WAY off. No wonder I was chasing my tail. Someone had changed things and failed to tell me. Anyhow, here is the base idle reset I used by tmoss (2nd one down): http://forums.stlmustangs.com/index.php?/topic/36545-idle-reset-procedure/

    After swapping out the parts and setting the idle I drove the car. It ran smooth as silk, idled rock steady at about 600, and the rpms returned to idle immediately when I took my foot off the accelerator. Moreover, there were zero trouble codes KOEO/KOER after the test drive; thank the Lord.

    Moral of the story: check this site for helps, get Motorcraft parts when it comes to sensors, try not to let your local mechanic touch your car if at all possible, and thank the Lord!

    I hope this craziness is helpful to someone else with the same/similar issue.
    #19

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