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Thread: XR7 Mystery

  1. #1
    Join Date
    Aug 2011
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    Sikeston Mo.
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    15

    XR7 Mystery

    Hi to all, I just bought a 89 XR7 two weeks ago. This is my first SC car. The guy I bought it from told me that a little over a year ago the car ran great, then one day he parked it and he was never able to get it to start again. I got the car home and tried to start it, it would crank and backfire like the timing was off, so I advanced all of the plug wires like I would have back in the day and the thing started and ran. It didn't run very good but it did run. I assumed that the timing chain had slipped so I tore into it and found that the cam timing was dead on. I went ahead and changed the timing chain while I had it down. After I got everything back together, I still can't get the car to start unless I swap places with the #1 and #3 plug wires and #4 and #5 plug wires. I've read the forums about how if you unhook the cam position sensor, and try to start the car, the ECU will randomly select different cylinders untill the engine will start. I've tried this several times and the car absolutely refuses to run with everything wired correctly. Does this sound familiar to anyone? When I wire it backwars and run it, the engine sounds smooth but I dont think the power is where it should be. I'm guessing it won't be untill I can get everything working in sync so the fuel and timing are correct. Any help would be greatly appreciated.

  2. #2
    Join Date
    Mar 2005
    Location
    Millville, MA
    Posts
    121
    I would check your harmonic balancer, could be broken. Only two times have I had a backfire, once was a broken balancer and the other I had my plug wires wrong.

  3. #3
    Join Date
    Apr 2002
    Location
    Madison, Ohio
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    17,540
    Check your firing order and do NOT change the wires under any circumstances. The plugs are fired off the crankshaft, not the cam so the timing chain has no impact on firing.

    Some diagrams are wrong. Do some research and locate the correct firing order and double check. Coil pack should be 1-2-3 across the back and 5-6-4 across the front. 1&5 are paired, 3&4 are paired.
    Quote Originally Posted by Miller View Post
    Ya thats why i tape mine down. People think its bc i dont have a moonroof seal (which is true) but its really to keep my roof from ripping off .
    Email me here.

  4. #4
    Join Date
    Aug 2011
    Location
    Sikeston Mo.
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    It is very possible that this engine could have the wrong parts on it. Evidently the previous owner tried swapping parts around from another car he had. most of the things I've checked so far have been loose. locks broken on nearly every electrical connection, etc. The crank position sensor is supposed to be new. I have checked and double checked my plug wire locations. When it wired correctly- 123 across the back of the coil, 564 across the front it will not start at all. wired 321 across the back and 465 across the front the car starts right up, idles great . runs down the road smooth, but the throttle feels somewhat lazy. I'm wondering if the car could have the wrong balancer on it and maybe the metal tabs on the back are indexed differently? Don't know if thats even a possibility.

  5. #5
    Join Date
    Dec 2002
    Location
    Wintersville, OH
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    4,072
    is the coil pack on backwards, connector on the firewall side?
    Making woosh sounds since 2010!

  6. #6
    Join Date
    Jul 2003
    Location
    Eastern (nee Western) PA
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    4,991
    Might be a bad vacuum leak, although it wouldn't match up with the story that it ran, then was parked, and then wouldn't run.
    God bless!!!

    1990 SC auto ... red outside, gray cloth inside ... ~205,000 miles (and climbing) ... driven daily!

  7. #7
    Join Date
    Aug 2011
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    Sikeston Mo.
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    Quote Originally Posted by neverfastenough View Post
    is the coil pack on backwards, connector on the firewall side?
    Yes connector is on firewall side. Is that backwards?
    Last edited by stroker351; 08-19-2011 at 04:48 PM. Reason: after thought

  8. #8
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    Eastern (nee Western) PA
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    Quote Originally Posted by stroker351 View Post
    Yes connector is on firewall side. Is that backwards?
    No, that's correct.
    God bless!!!

    1990 SC auto ... red outside, gray cloth inside ... ~205,000 miles (and climbing) ... driven daily!

  9. #9
    Join Date
    Jan 2008
    Location
    Springfield, MO
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    679
    you say you have to wire it "wrong" to get it to run... which cylinder are you calling number 1? Number one is on the passenger side front... Number 4 is driver side front... so it's like this...

    Firewall
    3 6
    2 5
    1 4
    Radiator


    perhaps your thinking the cylinders themselves are numbered differently?

  10. #10
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    Aug 2011
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    Sikeston Mo.
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    Quote Originally Posted by 351cat View Post
    you say you have to wire it "wrong" to get it to run... which cylinder are you calling number 1? Number one is on the passenger side front... Number 4 is driver side front... so it's like this...

    Firewall
    3 6
    2 5
    1 4
    Radiator


    perhaps your thinking the cylinders themselves are numbered differently?
    No, I've got the plug wires right. Did quite a bit of checking yesterday and have decided to pull the balancer later today and see if the vanes are somehow put on wrong. Almost has to be something around the balancer.

  11. #11
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    Aug 2011
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    Pulled balancer today. Found a picture of a new one on the internet and compared the two. Mine looks identical, outer ring of the balancer has not moved, nor is the vane mounted incorrectly. Good news though, I did find somebodys 13mm china socket laying in the crossmember...life is good!

  12. #12
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    Jan 2008
    Location
    Springfield, MO
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    Is the cam synchronizer/sensor timed correctly? I've seen those cause some weird issues... There should be info here somewhere of how to time the synchro correctly. If not, i can look in my shop manual software tomorrow and post it... Also is there a chance that the connector to the coil pack is on upside down? u said all the lock clips are broken... another "out there" idea, lol...
    Last edited by 351cat; 08-21-2011 at 10:06 PM. Reason: grammatical error

  13. #13
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    Quote Originally Posted by 351cat View Post
    Is the cam synchronizer/sensor timed correctly? I've seen those cause some weird issues... There should be info here somewhere of how to time the synchro correctly. If not, i can look in my shop manual software tomorrow and post it... Also is there a chance that the connector to the coil pack is on upside down? u said all the lock clips are broken... another "out there" idea, lol...
    Yup, Got the syncro timed...thanks to sccoa members, lots of good info and pics here. Just went out and checked the plug on the coil pack, of course it's broken but no it's on right, plug is made so that it can't go on backwards. Did notice something however, from the pics I've seen of these engines, the plug for the coil pack is vertical. The plug on mine plugs in horizontal. I wrote the part number down that's on my coil pack, going to research now and see if it's the right coil pack. like I said earlier, the guy I bought the car from also had a SHO taurus and another cougar that I'm pretty sure he had been switching parts around on.

  14. #14
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    Quote Originally Posted by stroker351 View Post
    Yup, Got the syncro timed...thanks to sccoa members, lots of good info and pics here. Just went out and checked the plug on the coil pack, of course it's broken but no it's on right, plug is made so that it can't go on backwards. Did notice something however, from the pics I've seen of these engines, the plug for the coil pack is vertical. The plug on mine plugs in horizontal. I wrote the part number down that's on my coil pack, going to research now and see if it's the right coil pack. like I said earlier, the guy I bought the car from also had a SHO taurus and another cougar that I'm pretty sure he had been switching parts around on.
    Yes, the stock coil pack has a vertical plug. The coil pack is pretty low-tech, though ... so I am not sure how much difference it makes. Most of the ignition system's brains are in the gray ignition module box above the AC compressor.
    God bless!!!

    1990 SC auto ... red outside, gray cloth inside ... ~205,000 miles (and climbing) ... driven daily!

  15. #15
    Join Date
    Aug 2011
    Location
    Sikeston Mo.
    Posts
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    My manual says the DIS determines firing order. The way I'm having to wire this thing to get it to run means the firing sequence is completely backwards. I think my next step is to go ahead and replace the DIS. My next question is, am I better off using the Motorcract module or are the aftermarket modules satisfactory?
    From what I've seen so far from this engine, I think I have decided to go ahead and pull it, go through it and make it right. It has a rod noise, the oil pressure drops when it gets to operating temp, and the water pump was out when I got it. I don't really trust putting the car back on the road without first tearing into it, and at the least replace the bearings and head gaskets. I will more than likely do a complete rebuild while I have it out. I've ran it enough to know that the auto trans. shifts out fine and doesn't slip. The car has 134,000 on it and the body is straight and the interior is super clean other than needing a headliner. I would like to get this timing issue thing worked out before I pull the engine. So I'll order a DIS tomorrow and try that next. In the mean time I think I'll start another thread and get some input about an engine rebuild. Will post back here after I get the new DIS put on.
    Thanks again Guys.

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