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Thread: Garage kept one owner 40,000 mile 89 Cougar XR7 running rough need guidance

  1. #1
    Join Date
    Sep 2019
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    3

    Garage kept one owner 40,000 mile 89 Cougar XR7 running rough need guidance

    Hello all. My name is Tony and I live in central Virginia just Southwest of Charlottesville. I am posting here because I can't find anything in central Virginia, and I grew up in York County, spent a good 30 years between the tidewater and peninsula.

    I inherited my grandparents cars this year after my grandfather passed away. I am quickly becoming overwhelmed financially trying to get the cars back to reliable and fun condition. One of the cars is an 89 Cougar XR7 SC - cousin of the Thunderbird SC. Same engine and trans as far as I'm aware.

    This car has been garage kept since day 1, and after my grandmother passed in 2015 my grandfather didn't ever drive it, just started it in the garage and let it run for a while, then shut it off. This process was once a week on average for 3+ years. It ran rough for at least those 3 years while it idled in the garage. But now that I have it, I have had it in 2 shops, replaced numerous parts to the sum of about $1100 doing most of it myself.. no luck. The car idles horribly. It runs fine when you first start it, nice and smooth, rpms where they should be, etc.. then as soon as it warms a little, 10-20 seconds, the idle drops to around 650-700 and it runs very rough. Has great pedal response, but when you let off the pedal the rpms drop and it acts like it was to shut off then immediately kicks back up to 650ish rpms and resumes running rough.

    Driving at 45-60 mph it seems smooth, unless the AC is on, then it seems to buck a little when the compressor cycles (low freon, but has the silly Ford only low pressure adapter and no shop around has a way to charge it, or a conversion for it. But I don't usually run the AC anyway so I am not worried about this right now. Only the rough idling - to the point where you can watch the engine "rock" a little under the hood.

    I have replaced so much as suggested. There is NO check engine light. It only came on once or twice under WOT from a stop, then as soon as I let off the gas pedal it was gone. Nobody has been able to pull any codes, or find anything wrong electrically, no vacuum leaks, supercharger piping resealed with correct teflon gaskets, etc.

    There is a new MAF sensor, coil pack, plugs, plug wires, cam position sensor, thermostat, engine coolant temp sensor, radiator, DIS module, etc. I have spark from all positions on coil pack, spark to all plugs, proper motorcraft plugs and wires, I have tested the radiator for exhaust gases with a good block tester, no coolant and no sweet smell from exhaust pipes (no smoke from pipes, but it does smell a little rich on initial start), I have the correct fuel pressure that I am supposed to have at idle. I have run 2 tanks of quality premium gas through the car, one with Seafoam (first shop said bad gas from sitting so long), second tank used Lucas fuel injector cleaner. I have checked the injectors for function with a Quick Fuel Injector Tester (pulses and beeps with the motion of each injector).

    I am just at a loss with this car and I do not want it to sit and rot in my driveway. I would like to get this car running again but there just doesn't seem to be anyone out here who understands these engines, and I am at the point where I am willing to pay to have it hauled to a shop that knows these cars if I can ever find one. I have spent about half the cost of an engine replacing parts that haven't fixed the problem.

    As a side note, may not be related, when you step on the pedal to make the car downshift and go, it downshifts after about 3/4 throttle, and only lasts a second or 2 before it shifts back into regular gear. It will not maintain "passing gear" at all.. just goes right back to regular drive (3rd I believe), if you maintain 3/4 throttle or more, this is when the check engine light has come on twice.. but immediately goes away as soon as you let off the pedal. And I tried to check the timing with my Innova Pro, but when I connect to the #1 wire, the light is very erratic and not a constant flash. It "walks" all over the place, the timing mark goes between 0 and off the marks completely on the advanced side. But when I connect my inline spark tester, the flash is fast and constant just as with the other 5.

    I am an OBDII and old school carburetor mechanic. I know nothing about OBDI to the point where I refused to buy project cars because they were OBDI, I only have this car because I inherited it, and I am headstrong about getting it fixed for my grandmothers memory. I feel like I am so frustrated with it that I am overlooking a very simple problem/solution. If this car wasn't in fresh off the lot condition I would sell it for money to put into my grandfathers 70 camaro that I am also working on.. but I would get very little the way it runs currently.

    I just need to get this car running right, at which point I would love to drive it and take it to some shows and meetups. I would love to get this handled myself with some guidance, but I am absolutely fine sending it to a qualified shop/mechanic in Hampton Roads or anywhere in Virginia if need be. The parts i've replaced that haven't fixed the issue would have already covered transporting the car twice!

    If there is an SC guru here that can spare some time for me, I would greatly appreciate it.. or if anyone knows a shop with a supercoupe/xr7 genius, help me get in contact with them please!

  2. #2
    Join Date
    Apr 2002
    Location
    Madison, Ohio
    Posts
    17,642
    Welcome to the SCCOA, hope this car works out for you in the long run.

    As for your issues, the biggest one sounds like a dead ringer for a vacuum leak. Easiest way to find one would be by performing a thorough smoke test on the intake system. Typical leak points are the intercooler tubes, and the large vacuum lines behind the inlet plenum.

    The old gas isn't helping, and it is possible to have a sticking or clogged injector even though your noid tests turned up good. If one is sticking it would be typical to see fuel pressure drop quickly after you shut off the engine. If one is clogged, then you'll see fuel trims uneven or excessively high during highway cruise or acceleration. But OBD1 scanners are few and far between so that might be a bit hard to verify. Not common to have injector issues so I kinda doubt this one.

    The transmission shifting is probably semi normal for this car, but check the kickdown cable at the throttle body and make sure it's still properly engaged in the bushing where it attaches to the throttle shaft arm. It's common for these bushings to dry rot and fall off leaving the cable loose which will destroy a transmission quickly. But upshifting super early is common. People often adjust these cables a little bit tighter to get a more aggressive shift action.
    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.

  3. #3
    Join Date
    Sep 2019
    Posts
    3
    XR7 Dave,

    Thanks for the reply and sorry I haven't posted back sooner, work has kept me very busy.

    I purchased a smoke machine and disconnected the large vacuum line that runs over top of the master cylinder to a check valve, it connects to the fitting that stands vertical at the back of the supercharger (fitting is on the SC pipes, just over the EGR location). When I introduce smoke at 1-1.5psi I get smoke coming from the diaphragm vents on the bottom of the NEW egr vavle, each of the little holes.. however when I put 7-10 inches of vacuum on the line connected to the EGR that seems to stop until the smoke machine pressurizes things back up.

    Also, after blocking off the throttle body air intake side, and running the smoke for a few minutes, I have a steady stream of smoke coming out of the oil dipstick tube.. is this normal? I have smoke tested a few cars at the shop years ago for vacuum leaks, been very successful, but I do not recall ever seeing the smoke introduced into the vacuum tubes start to come out of the oil dipstick tube.

    Good news is that I still don't see smoke from vacuum lines, valve cover gaskets, or around the intake. Only on the bottom of the EGR without vacuum going to it, and then coming out of the dipstick tube.

    My vacuum at idle is still hovering around 15 inches in park, and between 12 and 10 in drive, so I am sure something is going on, but again no smoke from supercharger pipes or intercooler.. or anywhere other than these 2 places.

  4. #4
    Join Date
    Apr 2002
    Location
    Madison, Ohio
    Posts
    17,642
    I have re-read your initial post and realize that you have actually done more work than I first paid attention to. After a lot of thinking I keep coming back to one or two conclusions.

    It's possible there is a mechanical issue to where it simply isn't making compression on all cylinders. It does happen some times that you get rust in a cylinder or behind a valve that was open while the car was sitting and pitting is too deep for them to really seal again. The only way to determine this is through a compression test which I know sucks to do on these cars. They should be even and around 150-160psi. Remember to keep both the throttle body and the supercharger bypass valve open if you do a compression test as air does not flow through the supercharger very well when it's not turning.

    The other possibility that I'm considering is the ECU might actually be bad. It's not common, but I've seen it. The reason I suspect this is the CEL on full throttle. There are very few actual problems that will cause a CEL on WOT, and few will have anything to do with idle which is where your problem is most prevalent. I suspect this also because it seems like it's not going closed loop. Typically if you have a rich condition on start up that gives you a smooth idle, then as cold start fuel is pulled away it starts to run rough, that will be shortly followed by closed loop richening it up significantly and getting that idle back. It seems from what you say it never tried to correct. I suspect it may never be going closed loop which points again to the ECU. If during the time it was stored the battery went completely dead, it could have resulted in damage to the ECU. I've seen this happen on low mileage cars. This is pretty easy to swap out, I have extra's if you need one to test.
    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.

  5. #5
    Join Date
    Sep 2019
    Posts
    3
    It would be easier to test swap the ECU than to do a compression test. I am all for trying another ECU because this car has indeed gone through a battery or 2 since it was sitting, and when I had it hauled to my house I had to get a new battery for it. He was pretty good about putting the trickle charger on his cars, but I do remember when we were getting the cars prepped for hauling that I hooked up his 1980s sears battery charger it went through a phase where it came on, turned off, came on turned off, then it made a funny noise and wouldn't turn on anymore. I have a feeling this could have shorted internally and caused an issue? All I know is after that the battery wouldn't turn on lights or anything. So either the battery shorted internally and fried the charger, or the charger shorted and fried something.

    I am willing to try an ECU if you have one for an automatic (if that matters with these cars).. let me know how much to borrow an ECU and Priority/2/3 day shipping, and however you want to handle payment (paypal invoice, or whatever you prefer).

    If the ECU doesn't work then compression testing will be next.. not looking forward to that after doing the plugs and wires and realizing how they really could have engineered the engine or the engine bay itself to make this a less difficult task.

    Thank you!

  6. #6
    Join Date
    Apr 2002
    Location
    Madison, Ohio
    Posts
    17,642
    Send me an email at [email protected]
    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.

  7. #7
    Join Date
    Jul 2002
    Location
    Roanoke, Virginia
    Posts
    3,348
    There are a few of us here in Virginia if you want another set of eyes to look things over also if the ECU doesnt resolve your issues.

    I'm pretty covered up till December with work but always willing to make a road trip from Roanoke to help another enthusiast.

    -Tim
    Current Collection
    1994 Thunderbird SC - Auto converted to 5spd

    1995 Thunderbird SC - Auto

    1994 Thunderbird SC - 5spd
    1989 Thunderbird SC - 5spd - Daily Driver
    1990 Thunder/Cougar XR7 - 5spd
    1994 Thunderbird SC - 3v Project

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