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Old 10-11-2005, 10:30 PM
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1985 Ford Ignition Problems

I am working on a 1985 Crown Vic. that has a new cap, rotor, wires, plugs, air-filter, and fuel filter. The only problem that I can find with it is that there is a leak in one of the smog-pump lines and you can hear that noise they make! But I cannot imagine that causing the problem: The car seems to be running fine with no miss or anything and then all the sudden it will stumble. Even if you are cruising at 40 if you let off the gas and coast the engine will stumble as if it completely dies and then comes back to running. If you pull up to a stop sign it will die. Anybody know anything I need to check? Something that I forgot to say was that the check engine light works but is not coming on. Is it possible for codes to be stored in there and not light the light? I know some newer cars have codes that do not trip the light but I don't think any of them are things that can actually make the car die. But I am not sure. Any idea is well appreciated.


Last edited by Bert420Chillin; 10-12-2005 at 12:10 AM. Reason: adding information
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Old 10-11-2005, 11:59 PM
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Doc here,

I am NOT a Ford guy at all...Hopefully someone who is here (and we have a bunch of GOOD ones here) will have an answer for you..

HOWEVER, with what you said about the smog pump noise, If it were a GM...
(I've have several that do this over the years on AIR)

That noise will get louder and the engine will run like "Crap in a Can" and throw a Check engine light" all at the same time..

If I recycle the KEY quickly on the run, the light goes out , it runs smoothly and you can't hear the pump you might want to try that to verify the problem..

(what is making the noise..I found it was a bad Valve on the Exhaust manifold feeding back into the diverter)..

But that's GM..not Ford, which I sure differs..

Hopefully the Ford guy's will chime in with a better answer...

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Old 10-12-2005, 11:01 AM
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I would check the idle air control/IAC. Sounds like its not working.

I dont think the computers were smart enough back then to store fail codes if there wasnt an active fault.
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Old 10-12-2005, 04:50 PM
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'85 would be carbbed right, check the spark box ( I think they called it a duraspark, not shure ), the Ford LTD/ Crown vic's had lots of problems with those in the 80's, you should find the box in the right or left side front of the inner fender in the engine compartment. There not an expensive thing to replace but get a good 1, Napa's lasted my grandparents a lot longer than carquest's did. They had a '80 or '83 or somthing LTD w/ 302 2bbl ( same car basicly as yours ) and the car would not start if you shut it off, let it sit and it would fire up, the problem was caused by the spark box being bad, they must have put 10 in the car b4 they got rid of it ( the carquest 1's burnt out faster than the napa 1's ). I'v heard they will start to go bizzurk too.
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Old 10-12-2005, 07:59 PM
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Is that a carb or EFI 5.0L? Does it have cruise control and does it work? If you have a multimeter, check the Throttle Position Sensor (if it's EFI). Should have a 3 prong connector on it. Between the middle and each side, one side should increase in resistance and the other side should decrease in resistance as the throttle is opened. I had a 1994 Oldsmobile 88 (was a POS that I only kept for 2 months but that's a whole other story) with similar issues, the only tip off I had was the cruise control that pointed to the TPS (Throttle Position Sensor).

The folks over at www.crownvic.net will be able to help you.
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Old 10-14-2005, 12:44 AM
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1985 should be the EEC 4 system with a throttle body fuel injection system. Most common problem on that model with that symptom is carbon particles sticking in the egr valve. Remove the egr and clean the seat. Check the egr valve sensor with an ohmmeter. With the egr sensor off, push in and out on the pintle while monitoring the ohmmeter. Also check the TP sensor like novaman says.
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