'91 GT Starts then dies after starting on a warm engine....

Discussion in 'Fox 5.0 Mustang Tech' started by 91StangGT5.0, Apr 30, 2010.

  1. Who cares about who said what.....let's be adults here. I'm more willing to trust HISSIN50 over ANYone on this forum particularly to the fact that his answers have solved all my problems....Though I'm not going to doubt your knowledge of the subject, but I did buy a new MSD TFI module for my MSD Super Billet Distributor and it didn't solve my problem. It wasn't the solution in my case, though it could have been....that's auto troubleshooting for you.

    HISSIN- It will start up as in the usual rpm jump when it starts but the part where the rpms drop back down it dies. So really it doesn't hold long enough to idle. Also I'm still confused on how to "check the ECT" I have a Aftermarket Mechanical Gauge and it runs no hotter than 185-190*.
  2. Ford IAC's are pricey but if you happen to have a spare one around, I'd try it. When the duty cycle kicks down from the initial high idle, the IAC doesn't sound like it's bypassing enough air.

    For the ECT, back probe it while it's connected (KOEO is fine). You'll see ~5.0V on one wire. Ignore that wire and check the signal wire. It should show about 0.50V at ~200*F (the voltage increases as temp decreases). If you're testing it on a cold engine first (what I'd do), that same wire should show about 3.0 volts at slightly more than room temp.

    The sensor can be out of calibration but not out of absolute spec. It's very unlikely this is the issue but it's worth that thirty-second check.
  3. Is there a wire to ground to or should I just ground the voltmeter somewhere else like the chassis or elsewhere?
  4. I have a space IAC if you would like to borrow to see if it resolves your problem? Not sure where you are located. I'm in the Dallas area. Let me know.
  5. The negative battery connection is ok to use.
  6. Oh I've also noticed that this problem started after I changed my exhaust header gaskets......before I changed them it was leaking and my idle wasn't too great, but when I changed them it straightened both out. Maybe O2 Sensor?
  7. did you disconnect your battery ground for a while to clear your KAM after you did that exhaust repair?

    It's probably not going to fix your problem, but it's a good thing to do when you do something like that.

    If you think it's an o2 sensor maybe you can find a way to force the car into an open loop to see how the car runs when it's not using the inputs from the o2 sensors
  8. It could be an O2 Sensor as I smell the slight stench of gas when the car is running....I don't have the Charcoal Canister hooked up though so the smell could be coming from that...What is "Open Loop"?

    And Yes I did clear the KAM. The battery was disconnected and the headlight switch was on the whole time I was working on the car....kind of overkill but I needed to ensure it was cleared.
  9. Open loop us a mode the PCM is in where it doesn't rely on inputs from o2 sensors. This is generally on cold starts because the o2 needs to be hot to function properly and when you're wot the PCM will go into open loop.
  10. Have you checked your ignition timing? I just had this problem with a 92 coupe I just bought. The base ignition timing was at 22 degrees and it was doing exactly what you describe. I set base ignition timingat 14 degrees and it restarts and idles fine.
  11. How do I find out where it's set at? I've never messed with the timing nor have I ever set the timing. My mustang is pretty modified and has higher compression (~9.5:1ish-10:1ish). I don't even know what my timing is supposed to be set at honestly haha. It's been fine as it were it is....supposedly.
  12. If you have the stock balancer it could be a bit of a chore, as the origional timing marks will be hard to find. you will need to bring the engine up to tdc on the #1 piston and mark the balacer on the timing tab. Get a dial back timing light and set itany where from 10-14, Ford calls for 10 degrees, more modified engines like a bit more but as a rule of thumb dont go over 14 or you could experience problems like you are having or over heating etc.

    Let the engine warm up then unplug the spout connector , the 2 wire plug near the distributor that goes no where but into a little square plug. loosen your distributor and turn it until your timing mark at 0 lines up with your timing tab. Make sure your light is set at 10-14 degrees.

    You might get luckey and be able to see your 0 mark on your balancer without establishing tdc. It will be on the part of your balancer that is notched out for the external imbalance. There is 3 holes in this part of the balancer. 0 or tdc is just to the left of the center hole if you are looking at the engine from the front.
  13. Very helpful! So the degrees come from the markings on the harmonic balancer? That is where I was confused about timing was where "degrees" was coming from.
  14. Yes, the reference about X degrees comes from those marks scribed into the balancer.
  15. ditto this on my stock 86GT
  16. I ran codes again today and got codes 85, 33, and 96 on KOEO on KOER I get just 33, 44, and 94 mostly because I'm not using the EGR and Smog Pump. I also ran a Cylinder Balance Test and it passed all cylinders three times.
  17. And the timing and idle were in spec and/or reset?
  18. I haven't tried that yet. Just wanted to get a video of the issue. I've been hella busy these past couple days.