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My 1987 Ford Tempo GL Coupe runs great at 169K original miles. But it has developed a bad habit that has stumped two different Mechanics and
cost me over $1,000. so far, to fix. Which by the way, no one can figure out what is going on.

The problem is that it doesnt idle, and quits going down hill, turning corners, stopping at stop signs, or any occasion where I take my foot off the
accelerator. Other than that, it runs and performs great. We have replaced everything from the jets backwards in the fuel supply chain, including
the engine temp control, engine control monitor, etc. And yet it dies. I will enter full list of everything tried or replaced, later today. Any one with suggestion?

Really need this car for spouse to commute to work, any help appreciated.
 

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Found out there still may be a few one barrel carbed engines in that year. If so likely the feedback type (6149 Holley) and two different feedback systems used there, idle controlled by variable idle air bleed and main system controlled by variable power valve restriction. If the OP has that carb then fixing idle may be as simple as finding a vacuum or simple air leak in the idle feedback circuit or it may become a nightmare. I do not know what method meters the idle air to change it but likely may be chasing that.
 

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The problem is that it doesnt idle, and quits going down hill, turning corners, stopping at stop signs, or any occasion where I take my foot off the
accelerator.
I had the same problem with mine, and the problem turned out to be "false air", e.g. leaks in the intake system from bad PCV grommets and the EGR valve was worn out. When pulling the codes out of the EEC-IV, there were none stored. KOEO normal, Run and Continuous all normal. I was starting to pull out what hair I had left!

Additionally, when I set the ignition timing, my Haynes manual said 10 deg. BTDC. What it didn't say was that's the spec for the Manual Trans, and I have the Automatic.

I had to go back to the Ford Shop Manual and discovered that my '86 Tempo needs 15 Deg. BTDC with the auto trans.

I changed the grommets at the PCV valve and at the breather tube (opposite side of the valve cover from PCV valve), the PCV valve itself, and the EGR valve. The PCV grommet is still available, but I had to get a universal fit one for the breather side. I think it was meant for a GM car, IIRC. 3/4" I.D. hole, 1" hole in the valve cover. Tight fit, but it worked.

I originally thought the EGR valve was good, because it opened properly under vacuum, and didn't leak when trying to blow air from the exhaust side towards the intake side.
But trying to draw air in from the intake manifold side of the valve, there was almost no restriction! The diaphragm was good, but there's a linkage that passes through the body of these valves that goes to the sensor on top of the valve. At that point, it leaked worse than a sieve.

There was a very noticeable difference between the old valve and the new one. I talked to an online mechanic, and he said that EGR valves tend to leak a little, not a problem. I could still draw a little air through the intake side of the new valve, but nowhere near what the old valve was passing.

The situation was much improved with these repairs, but would still occasionally die. It took about 2 weeks of driving (not every day) for the EEC-IV to re-learn and re-adjust itself to the new conditions.

Now, the car runs great - no more dying at lights, stop signs, or anything. :grin2:

One last note on this car, it's been in the family since it was new in 1986, and has wound up the first car of about every kid in the extended family, so you can imagine what it looks like. The poor engine has quite a bit of blow by, but you'd never know it from the way it runs now. My daughter presently drives it, and there's no way I'd turn her loose in a car that could leave her stranded!

Hopefully, this will help someone else out there who is having the same problems.
 
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