Idle Problems.. new thread for problems

Discussion in 'Fox 5.0 Mustang Tech' started by savegoodautonfg, Jul 31, 2007.


  1. savegoodautonfg

    savegoodautonfg New Member

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    No i dont. the one thing i know it has to be an electrical problem because the fact that when i turn the car off and on it resets and its ok for a bit until it does it again.

    The last thing I checked was the TPS voltage and it is at 1v yesterday i looked at it.
  2. patrickmx2

    patrickmx2 New Member

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    Could be a grounding issue too. You need a good block to chassis ground and a block to battery ground. Then an EEC harness to battery ground. Also a 10 or 12 gauge battery to chassis ground. On a 15+ year old car, trust me, run all new grounds. $25 to $30 at the most.

    The EEC grounds in a couple of places. I'm talking about the one up by the battery. Just check it out and run one from the battery to that point on the fender apron.

    The EEC has a ground in the passenger side kick panel. The HEGO ground is on the back side of the engine block. There is a motor to firewall ground there too. Just leave it in place and possibly clean it.

    I run 2 4 gauge wires from my fender frame channels to my engine block on each side. Like 24 inches or 30 inches will do. The cables are like $5 and have an eyelet at each end for a bolt.


    Now... your idle hang problem. If KAM's (keep alive memory fuel trims) have built up your idle might be hanging after it has run a awhile. It's compensation for problems. When you shut it off the process starts over. KAM's arent erased but still there until you pull the battery.

    First if your hardware is good, check the grounds and repair, reinforce. If you are confident your sensors are good that leads me to grounding / voltage.
  3. savegoodautonfg

    savegoodautonfg New Member

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    I need picture to show me where i run the new grounds cause i'm really confused by what your saying.

    Since I got Code 34, maybe my EGR valve and sensor is bad. would it cause this problem?

    Also just so you know, i just got a new Fuel Injector Harness.
  4. savegoodautonfg

    savegoodautonfg New Member

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    The other day i turned my car on after it was sitting for an hour and as soon as i turned it on it started hanging like 30 seconds after.
  5. patrickmx2

    patrickmx2 New Member

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    I'm headed out to my shop and will snap some tonight for you. Well you've got two sensors out of range for sure but if current related, ground, etc... then you can get some really messed up results.

    Example: Guy rolls up to my house in an 89 GT. He has owned it 14 of those years and been a perfect car. Well it starts popping between shifts. No codes. All sensors check out and he has even taken it to TWO Ford dealerships, one of which a friend of his works at and he made a special trip there since it was further away than the close one but neither could find a single problem. The thing is people tend to just make visual inspections with some of their meter diagnostics and code pulling.

    So he drives an hour to my house next. I reach down and grab a large 4 gauge ground wire that "looked" good. It was loose. So loose that it caused current to run to another factory ground and burned it in two. They assumed the added ground was fine but it wasn't.

    This cured his alternator issues right away too which was a problem he didnt really acknowledge yet. He had already also had the TFI unit checked and replaced it anyway.

    The problem was two fold.
    One: the loose engine ground caused false signals and an irratic idle occured.
    Two: A TPS that was failing but still good was causing the back fire and pop between gears. The only way to find it was actually data logging and watching it. I put it on a meter and could not duplicate the false readings. It was only during operation that it was just off enough that it caused the popping due to incorrect timing at the wrong time.

    I'll get back to you later on tonight.
  6. savegoodautonfg

    savegoodautonfg New Member

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    If you could honestly take pictures and draw arrows of where i have to run the wire, ill definetly run new wires tommorow.
  7. patrickmx2

    patrickmx2 New Member

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    This is the basic 4 gauge common battery cable with two eyelet ends. Note the comments in the pictures and in between the pictures. Also notice I have two different cars, one with a rear mounted battery but the pictures are clearer using one car for some of them. Same principle applies. I don't have them pictured but I have duplicated the block to chassis ground on the passenger side of the engine. I find that engines that are abused or have rough idles tend to shake, twist and so on so on. I check my grounds on oil changes.

    [​IMG]


    This is the power steering bracket. Notice there are two cables grounded here. One goes directly to the battery. The other to the frame rail in the next picture (third picture down)

    [​IMG]

    Frame rail ground.

    [​IMG]

    Notice the SMALL wire coming from the Battery negative and where it leads too. In the last picture I'm using the other Mustang you'll see two wires. One is the EEC Main Harness ground (FACTORY) and this ground which is also factory.

    [​IMG]


    This is your FACTORY EEC Main harness connector for ground.

    [​IMG]
  8. patrickmx2

    patrickmx2 New Member

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    bump... updated with photos
  9. savegoodautonfg

    savegoodautonfg New Member

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    Thank you.. seems to me your saying taht there should be 3 wires coming from the negative terminal of the battery?

    Also the 3rd picture down, where on the block does it go to?
  10. patrickmx2

    patrickmx2 New Member

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    2 wires coming from the negative battery post as in the picture.

    3rd picture down, refer to the location on the power steering pump bracket -its connected to the block so that is good enough. There is also an area on the timing chain cover that is threaded but hard to get to from the top side. ON the passenger side you'll see a threaded hole in the block too.

    CAUTION. When you start a bolt into these two holes if you use them you should be able to use your fingers to seat them and a wrench for a final twist. Do not over tighten or use a bolt with dirty threads. IF you do, you could risk splitting the block or timing chain cover holes and cause problems. That is just common sense with any bolt hole actually.

    Use any bolt you can find that isnt a header bolt due to heat. It's not that critical, you are just attaching components and making all your grounding common, that is all.

    Just think of your engine as an island sitting in the ocean. You need to build a path to land - chassis. Engine and tranny mounts are rubber isolated. Some people consider the driveshaft a ground. Until they see bushings with arc marks that look like someone dragged a welding tip across them.
  11. savegoodautonfg

    savegoodautonfg New Member

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    I need to buy a few of those duralast cables or what?
  12. patrickmx2

    patrickmx2 New Member

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    Two. One for each side of the block. One will do it for sure. The second is insurance.

    Add a smaller wire for the battery to framerail as in the pictures. This is the factory setup anyway so it should already have something close to what I'm talking about.
  13. savegoodautonfg

    savegoodautonfg New Member

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    Alright sounds good will do.

    one question tho, why would you think it was a ground, would'nt effect more then just the TPS?
  14. patrickmx2

    patrickmx2 New Member

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    That answer could fill a page. 100 symptoms have 100 likely problems. Grounds are the most overlooked part of any circuit in my experience.

    The question is, are yours good? Have you checked? You've gone through the trouble to change out the engire injector harness and replaced and checked several sensors. I could also ask why. Because the problem still exists.

    I'm not at all trying to give you a smart answer. I'm saying your answer is in your question. "Wouldn't it effect more than just the TPS". - at best that is an assumption.

    It PROBABLY is effecting more, but electricity takes the SHORTEST path to the best ground.

    I cant count the race cars and street cars with complaints about low flowing fans, dimmed lights and alternator upgrades thrown at a bad grounding situation. Too often people rely on that TINY little ground strap at the back of the motor to do ALL the load after they upgrade to electric fans and stereo systems, etc...

    To partially answer your question. PIN 46 on the EEC is a SIGNAL RETURN for many components. In the EEC for instance you have battery voltage vs. injector pulse table. Different volts which is effected by RPM at times especially during low idle can cause our injectors to get different PW (pulsewidth). This can cause surging idle, or missing. If you have a floating ground or weak ground, PIN 46 is getting different signals based on over all current flow.

    If the error codes isn't coming from the sensor, then the only other suspect is the current flowing through the sensor and that is usually a ground due to assumptions they are good.
  15. savegoodautonfg

    savegoodautonfg New Member

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    With these battery cables, all im really doing is removing old ones and putting in new ones.
  16. patrickmx2

    patrickmx2 New Member

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    at least connect the block to the chassis as in the pictures with the double eyelet cable. Even though you have a battery to block, I'm ONLY talking about the chassis to the block with a good HEAVY cable.

    Then insure you have a smaller wire from the battery negative to the chassis.

    That is only TWO wires to be clear.
  17. savegoodautonfg

    savegoodautonfg New Member

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    I just took a look under my hood. I have one thick cable going from the battery it looks as if it dips under the car and goes to maybe the starter?

    Then i have another one small one that goes from battery to the chassis and another wire comes out of the same connection to the chassis which goes to some connector it looks like.

    I can't see the block grounds nor do i know where the holes to put them into are?
  18. patrickmx2

    patrickmx2 New Member

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    This is a BLOCK GROUND. (I made my own)

    [​IMG]

    And it runs to HERE



    Again, JUST MAKE ONE. It takes 10 minutes.


    [​IMG]
  19. savegoodautonfg

    savegoodautonfg New Member

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    What battery cable do i have to buy for the ground that goes i think from the battery to the starter?
  20. patrickmx2

    patrickmx2 New Member

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    First off, that isn't a ground. Leave it alone. Leave what ever wires connected to your starter alone.

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