By on January 10, 2020

1989 Taurus LX Wagon, Image: Ryan the OPRyan writes:

I have another question about my 1989 Taurus LX wagon, but I wanted to let you know that your diagnosis of my automatic climate control was dead accurate. (Well yeah, I’m awesome like that. – SM)

I didn’t think it was the AC compressor clutch because I used a hot wire to put power directly to the terminal on the compressor while the engine was off and I could see the clutch pull against the pulley. But after your response I tried something different — I pulled the AC clutch power wire out of the connector to the relay module and connected power to that wire while the engine was running. I could see the clutch pull against the pulley, but it was slipping.

1988 Mercury Sable GS Wagon, Image: Ryan the OP

This was almost two years ago. You posted my question a day or two after my daughter was born, and I was also busy fixing my 1988 Mercury Sable LS (which needed a new heater core, ignition switch, battery cable, coolant, and I installed an FS-10 compressor and AC lines).

So anyway, that question for you:

In early December I took the ’89 Taurus LX for a test drive, and it started backfiring under light throttle when it was warmed up. There was either steam or smoke slowly rising from the lower back area of the engine. I pulled out the spark plugs and they looked terrible — worn electrodes and excessively large gaps — so I installed new ones and did a test drive again, with similar results. This time the engine stalled a couple of times, which might have more to do with the fact that I didn’t gap the plugs, so they’re a lot tighter than the .056″ gap specified. The check engine light isn’t on, and the temperature gauge is reading much higher than it should, but still in the normal range. I didn’t continue the test drive long enough to figure out if the electric fan was not coming on, or if the thermostat is not opening, or if the new water pump is bad. It’s hard to diagnose a leak because the car has sat outside for so long that condensation is on a lot of parts. I’ve changed a water pump before on this, and a 3.0 Vulcan engine, so I’m pretty sure I did it right, and I was careful about the orientation of the new thermostat. I know you’re not supposed to open the radiator cap when the engine is hot, but I did that anyway, and a geyser of rust-colored coolant shot up, so I know the coolant system is holding pressure. I’m at a loss as to why the engine is backfiring so badly after it gets warmed up. Could one of the new parts be defective?

Sajeev answers:

While I revel in my successful diagnosis (on a vehicle within my wheelhouse) I cannot contain my jealousy at your collection: the UR-Taurus/Sable had such a profound effect on my 9-year-old self.

On to your question: the odds that your mis-gapped plugs or cooling issues (you need to flush the rust, burp it, etc.) are the misfire’s source is unlikely. The source is likely one of the numerous wear items discussed here that are likely in any 30+ year old car. Especially, if I recall correctly, on a Taurus with well-over 300,000 miles on the clock!

So check them all: I’d start looking for vacuum leaks, testing fuel pressure (between 30-40 psi for these Fords), and cleaning the Mass-Air Flow Sensor (with the right cleaner!). Hopefully that works, but the link in the paragraph above is a pretty comprehensive to-do list.

And I know about such lists: after spending five figures on my (formerly) $900 1989 Lincoln Continental Signature Series I can say I truly enjoy the end result.  The Taurus was an amazing platform for the era, but it’s still competent performer and full of merit today!  Uh oh, I feel a Craigslist-style ALL CAPS rant coming on…

YOU TTAC PEEPUL FIND ME MINT CLEAN 86-88 MERCURY SABUL LS SEDAN RITE NOW 4 MY LINCO-TAURUS PLZ 1989 Lincoln Continental Signature Series, Image: Sajeev Mehta

[Images: Ryan the OP and Sajeev Mehta]

Send your queries to [email protected]com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice. 

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10 Comments on “Piston Slap: Bullish on Ford’s Electronic Automatic Temperature Control? (Part II)...”


  • avatar
    pwrwrench

    Ahh, the Mercury Table and the Ford Saurus.
    Yep, git that backfiring fixed ASAP. It could ruin the cat convertor or the whole exhaust system. Big $$$ in that case.
    What’s not mentioned is the possibility of burned/leaking valves. Do a compression test.

  • avatar
    pwrwrench

    BTW There’s a possibility that the dirty cooling system has some part in the backfiring. if the coolant does not circulate properly due to air pockets or blockage, the temp sensor will give an incorrect reading to the “computer”. Then all sorts of things can go wrong including fuel mix, ignition timing and idle control.

  • avatar
    PrincipalDan

    I wish you well, Amigo.

    Signed,
    Guy Who Loves Wagons

  • avatar
    StudeDude

    I agree with you regarding the effects dirty coolant might have. Which brings me to ask how an engine with a new water pump would have rusty coolant?

  • avatar
    Sigivald

    There’s nothing wrong with that Taurus that replacing it with a car that isn’t worn out wouldn’t fix.

    • 0 avatar
      SaulTigh

      This. I’m assuming that the Taurus wagon is the one with 300k on the clock (because that Sable looks really, really clean). That kind of mileage is way past the sell by date of these cars. I’ve owned three of them in my time, ’90 and ’93 Tauruses and currently a ’95 Sable. My personal experience, and that of people I’ve known is that these cars are good for 150,000 miles without too much trouble, especially with a lot of highway driving. 200,000 is possible with careful maintenance. Going much beyond that is hard unless you’re willing to replace/rebuild everything. I drive my Sable 2-3 days a week, but it only has 71k and some change on the clock, and lived a pretty pampered life up until I got it. I’ve been driving it like that for about 3 years now (with a 9 month stint as a daily driver) and it’s been remarkably trouble free. It’s got many more years of useful like in it the way I’m using it, but I’ve got no illusions that if I started putting say 15k a year on it it that it would hold up. They were good cars for their era, but they’re still made with 80’s technology and assembly techniques and to top it off they’re getting old.

  • avatar
    SPPPP

    Hmm, why is the coolant rust colored? Also, try letting the car warm up to operating temperature with the hood open, then feel the upper radiator hose. If it’s not hot, and if it doesn’t feel full of coolant, then that’s a clue that either the water pump isn’t pushing, or the thermostat isn’t opening. But I think the main problem is from something else.

    The “backfire” could be caused by a vacuum leak, which is definitely something to test. And it’s not hard to test – you can probably rent a gauge and get a few adapters from your local parts chain store.

    It could be ignition related. You replaced the spark plugs, so those are probably fine (even if you didn’t gap them). How about the TFI module? Those are known to fail on Fords from that era. Also, what about the spark plug wires? Those can fail and arc to the engine block or exhaust manifold, causing misfires.

    Fuel pressure is another easy check.

  • avatar
    pwrwrench

    Re. Rusty coolant with new water pump.
    Cooling system not cleaned when pump replaced. Not enough antifreeze in coolant. Many water pumps have a cast iron impeller which will rust rapidly in water without sufficient anti-corrosion additives. (Which are in proper antifreeze)
    Not using distilled or purified water in cooling system.

  • avatar
    MeanOldGuy

    How is this even a conversation, This is a 31 year old car, and an awful one at that, we need to enact mandatory removal of old cars past a certain age unless they have a significant contribution to the world as a collectible. You people bitch and moan about the environment yet drive this crap. 15 year rule needs to become law.

  • avatar
    Art Vandelay

    Oh man I love those Continentals. I worked at a L/M dealer back in the 90’s though and remember being surprised the first time I saw the hood up and the sideways 3.8…I had thought they were MN-12 based cars until I got to know them. They were no Mk VIII, but if you just wanted to tune out the world they were great and I swear roomier inside than a Town Car of the era.

    I don’t know anyone that came of driving age in the early 90’s and doesn’t have some formidable memory in a Taurus/Sable of that era.

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