Check engine light, stang runs like crap......

Discussion in 'SN95 V6 Mustang Tech' started by Gr0und_Fault, Jun 8, 2004.

  1. Nobody has a clue still, huh?
  2. Just a minor overview of the 3.8's ignition system and a few possible causes to your problem.And perhaps a little extra info to help understand how this thing works and as to why it would or would not cause a problem....feel free to whiz past any portion you find a waste of brain usage...

    There's a good possibility the problem could lie within the Ignition Control Module (ICM) itself.The ICM is connected to a Crankshaft Position Sensor (CKP) and also the PCM itself.The PCM is the brains behind everthing in your car but I highly doubt the PCM is causing any problems.The CKP sensor is mounted just behind the harmonic balancer (Behind crank pully).The sensor emits a small magnetic field that detects crank position and rpm by detecting a single gap on a spinning wheel with several teeth on it.,this would not cause your problem.As this sensor barely emits much of an output,it's impossible for this sensor to cause a fuse to overload.Ok now that you understand...getting to the point.

    3 wires (yellow) coming from the ignition module to the coils.They supply the ignition pulse to fire a specific coil.There are 3 coils,not 1.It is all combined in one unit.You know it as the coil pack.Each wire from ICM controls 1 seperate coil.The (red) wire from fuse (18) supplies a 12V power source for the Ignition coil pack.Also connected to this fuse is a Radio Interference Capacitor.This filters ignition RF from sensitive components and also your radio.I figured if this capacitor was shorting out and losing it's resistance it would be enough to overload the fuse.The only problem this could cause is a slight possibility of a surge current to the ICM if fuse was reconnected while key was on.But this is really a rare case.

    A faulty ICM would cause anything from engine hesitation,backfire..poor throttle response or it may not start at all.It's possible the 3 ICM output wires (Yellow) to coils could be overloading the coil primarys or the causing an excess drain on the Coil packs power supply (Red wire).Which in turn would also blow the fuse.It is not normal to go through Coil pack after coil pack.Something is definately overloading it.

    Run a diagnosis on the ICM,coil pack primaries (Yellows) and also check for continuity at the spout connector.If you don't know how to do this,check the Chiltons manual.Not sure if it has anything on that,if not,I have a Haynes manual with full diagnosis info on all parts of the ignition system.
  3. Thank you very much for replying MustangLX-5.0. I was thinking that it may have something to do with the ICM as well. I only guessed that and it's not an educated guess really at all because I really don't have any knowledge about ICM's. I tried disconnecting the radio interference capacitor, and the problem still exists. I checked my Chiltons manual, and I can't find anything on testing the ICM other than having to have a break out box, and a special harness to do any type of testing on it at all. I would greatly appreciate it if you could help me out with testing the ICM. Wether it's with scanned pages from the Haynes manual, or in typed text. Thank you for your help so far, this problem has really been irritating me since I've purchased the car, and any help is really, really appreciated!
  4. Not a problem.I'll post pics (Scans etc) and info on what to check and how.One thing though,I need a good image or file hosting site (Not a pay site) that can be directly linked to the files so they can be displayed here.Don't have a lot of room to stash them on SN.

    And reading your other threads here,i'm allmost certain your ICM is acting up.Coil packs dont go bad like that without something overloading them.The ICM's were common to bite it on older Fox body 5.0's.Being this is a V6 on a new style only in it's 2nd year,they were still using the old ICM's.Ford rid the stang of the ICM in '96 and later.The PCM controls all that in those later years.
  5. Thanks a bunch. If you want. You can always email them to me at my gmail account. 2 gigs of storage, I'm sure I'll have enough space for the photos. I just don't know what email you use. Some don't allow you to send big attachments. I think the limit for gmail attachments is 100mb. I dunno about the rest. I'm not sure where else you can host the files. Wish I knew.
  6. Where is the ICM located at anyway? I tried looking for it, and couldn't find it.

    [edit] Nevermind, I found it, it was under the mass air meter. I just need to find out how to test it now. I would just go buy the part and replace it, but the Murrays says the part is $299. Dang.......[edit]
  7. Oh Yeah, and for an update, I pulled up my OBDII code on, and they gave me a different message from what displayed on the OBDII tester I used. The code P1353 on the website says, "Ignition Coil B Primary Circuit" and when I used the scan tool on my car, the display read, "Manufacturer Contrl. Ignition System or Misfire".
  8. Ok, now this is really wierd. I took the ICM up to Autozone to get it checked and it checked out fine. I put it back it, and the car starts, but the rpms keep going up and down like crazy and it stalls out unless I give it some gas! The #18 fuse doesn't blow anymore either....odd......
  9. Sorry for the late response.

    Ok,I believe I have your problem narrowed down.The misfire and erratic throttle response...stalling....then blown fuse,which is all coming from the second coil within the coil pack itself.To be more specific,the coil that fires Cylinder #6 and Cyl. #2.

    The reason why this coil is acting up is due to the fact,the primary for Coil B is shorting to Ground or has a bad or possibly corroded connection.This connection problem or short could be in a number of places.First you'll want to check the electrical plug that goes into the coil pack.This connector is located on the back of the coil pack and has 4 wires coming off of it (3 yellows - 1 red).The 3 yellow wires are in order on the right side and the red is on the far left end of the plug.The culprit wire you are looking for will be the center yellow wire (Second from far right side).The terminal for this wire inside the plug could be loose or very corroded.Follow this wire all the way to the ICM.The wire insulation could've split from something rubbing or cutting into it.A bare spot exposed anyplace it's not burried in a harness could be touching or vibrating against the body or any ground.You'll have to look very carefully.Also check the connection on the ICM side.But this time check both the harness terminals and pins/contacts on ICM itself.No need to check the coil pack itself since basically it's known the coil pack itself is not the main source.

    Take your time on this one.If you can,have someone start the car and keep it running.During this time,follow the wire and all possible harnesses and wiggle it every inch untill you get to the ICM.You'll know if you hit an "Invisible spot".Careful around drivebelt and pullies.I once had my hand get pulled up between the Alt. pully and the belt.I was doing something to the pully itself while the motor was running and not being careful,the pully just slung my hand to the left and right into the belt track.The pully just sucked it right through an entire revolution and popped the belt off in the process.Believe me,It wasn't nice! So,you get the idea...back to wiggle test....Tell the person sitting in the car to keep throttle at a set spot.Just enough so it doesn't stall out.If you hit a bad spot,you'll know as your RPM's may smooth out or eratically change.

    This wire or the terminals on either end is definately your problem.Also it is what is setting the P1353 code.Let me know if you need more info.

  10. Thanks for all this help so far, it's greatly appreciated. I tried tracing back the wires as good as I could, but between the ICM and the coil pack, most of the wires are routed inside the engine body behind sheet metal. I checked all the areas were the wire wen't around a sharp corner, and I couldn't find anything. I even re-electrical taped as much as I could. problem still exists. I'm not an electrical genius, that's why I bring up this question. Anyway that this problem may be caused by a bad engine ground? I'm just curious. I haven't checked that out yet because I don't know where I should look for this. This was just an idea, I'm trying to check anything and everything at this point!
  11. Still no luck yet................
  12. Damn, that sucks, I think I'm going to have to take it to a shop. That really sucks because I hate having other people work on my cars. They are probably going to overcharge me wayyyyyyyyy too much too......
  13. Yeah, I had my brother try to help me yesterday look for the short. He was going to crank the engine over while I "wiggle" test the wiring to look for the short. The only thing is, that now my engine won't start. It cranks up like it wants to start, but it doesn't. That sucks. That really sucks, now it's going to be really hard to find it if I can't even get the car to start!.......
  14. Have you tried what I wrote in the PM I sent you a couple days ago regarding the tests with a multi-meter? If you need more info I can send you some NP at all.

    And I agree 150% on the thought of having a mechanic do the work and getting overcharged.That's why starting 4 years ago,I decided I wouldn't put up with mechanics BS and overpricing and just learn how to do everything myself.And that's exactly what i've done.I've done so many things,I lost count of it all.And saved hundreds..maybe thousands.Everything except for alignments and tires.No mechanic sets a hand on any of my cars.

    As frustrating I know this must be....and believe me,i've been through hell with electrical problems,I allmost kicked the drivers door in one night.

    You can still run the tests I specified in the PM.Just run a Key On - Engine Off test.

    If you need more info,any scans or pics of anything dont hesitate to let me (Or anyone else here) know.
  15. Yeah, I have tried what you sent in the PM. None of that worked. I got a good meter from work to use. I got about .015V going to each of the coils when I key on/engine off. When I tried to start the car, I got a very very small amount of voltage fluxuation. only about +/-.010V more (edit: I have full continuity going the coil pack wire harness to the ICM wire harness.). I did these same things on my Intrepid, and for the key on/engine off, I got the same results, but when I tried to start the car, I was getting battery voltage fluxuating at each coil, not just +/-.010V. I know the Intrepid is not a Ford, but it's the only thing that I had to reference it to that was readily available. I'm still thinking it's the ICM, but I took it off, and brought it back up to Murrays to test it again, and it passed 3 more times. The funny thing is that I was asking the guy testing the ICM a bunch of questions about the test, and he didn't know anything. Ok, well there was a few lights, for a few different tests. High RPM, Low RPM, SPOUT, Coil, and one other one. From what I saw, the tester only ran tests on my ICM for the first 3. Not all of them. When I asked the guy about it, he said, "Well, I guess that's the only tests that this ICM needs to have done to it". Anyhow, I'm assuming that that "Coil" test checks to see the voltage going out of the ICM, and to the Coil Pack. I may be wrong, because I never used that tester before, but that's what it looks like to me.

    (edit: the meter that I used was digital, but I used the High value, Low value recorder on it as well as just looking at the display while I turned the key, just incase I could not visually see the fluxuation of the voltage going to the coils.)
  16. Ok, well, I just swiped an ICM from my buddy at the junk yard. Put it in, and the car still doesn't start(or have any voltage sending to the coil back either). I'm just having bad luck I guess. At least I didn't have to go and buy the part from Autozone for $300! I'm hoping that it's not my PCM that's bad. I don't know how to check that either, but that seems to be the next on the schematic to check.......well, at least it looks that way to me.
  17. Ok, this is another update to all who care...I just barrowed an OBDII scan tool to scan for the codes on my car just to see if there was any new codes or not. The check engine light is still on, and I scanned the system, and it returns with no codes found. This is really really odd I think. Also, I just replaced the batter about 2 months ago, and it's already going dead on me again. This sucks......
  18. Ok, well I replaced the ICM, and no luck. Looks like I'm going to try the PCM next.
  19. Ok, scratch that, I'm replacing the CCRM if I can get to a junk yard tomarrow. Damn Chiltons schematics are all ****ed up. If they would have drawn their circuits just a tad better, I would have replaced this damn CCRM from the get go. I'm 99.9% sure that this is my problem!