Ford Contour V6 with intermittant miss

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BigD

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I have a 95 Contour 2.5 V6 115,000 miles with an allusive problem. What is funny is it passed the TX state inspection a day earlier! They ran it on a dyno. Starting cold it runs fine, but as it warms up, a miss develops. It threw a code once - 173 and 177 - rich bank 1 & 2. The problem went away for a week and came back last night. Fuel pressure is 30 at idle and 36 when the vacuum is off. Sometimes it has the miss at idle and sometimes it only misses only in overdrive under load. Yesterday the engine ran perfect. I stopped for a few hours, restarted, and upon leaving the subdivision, the miss came back. I had other problems with the engine last year so I did a upper and lower manifold rebuild (all the gaskets) to get rid of a vacuum leak. The coil pack, wires, plugs and O2s were replaced within the last 6 to 8 months. I cleaned the MAF because when it's dirty it will make it run rich - that didn't fix it. I would replace all the injectors but they are real hard to find for this engine. I had one go out last year.
 

Jim Fairbanks

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I would recheck it for a vacuum leak...also check the pcv valve..and the MAP sensor......Jim
 
B

bigD

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No vacuum leaks. When it did leak I got lean codes all the time and hesitation. Can has MAF not MAP sensor.
 
J

JohnD

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I'm not a tech, just an engineer with not one, but two of these sweet driving Contour sixes in the family. If I were you, I would recheck the plug wires, plug insulators, inside the plug boots, and plug bodies for carbon tracks, never sieze residue and corrosion. These engines have an extra high spark voltage, and will tend to arc over at the least opportunity. Especially under part throttle load. Clean with brakeclean and use silicon lube on the boots. Been there done that a few times.
 
B

BigD

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The plugs were changed a few months ago and the wires are Magnacore racing wires. I had a bad coil pack last summer, but it would miss only under load in high gear. Had to replace one injector last year when it totally failed.
Strange thing is this problem goes away after running a short while. I get rich codes which may be caused by an ignition misfire throwing unburnt hydrocarbons on the O2 sensors.
 

Transman

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Which brand plugs? The problem with ffford is they won't code a misfire unless it has gone forever and it is missing horribly, as a rule. Mode 6 has helped in this vehicle more than you know but I don't think a '95 will show mode 6 data. I think you need to get the info the old fashioned way, find a shop that has a scope or kv tester to see which cylinders are taking the most voltage to fire then you at least know which cylinder(s) are causing the problem. I have seen many autolite plugs do this though. Post back, Transman
 

autodr

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BigD said:
I get rich codes which may be caused by an ignition misfire throwing unburnt hydrocarbons on the O2 sensors.
No. O2 sensors don't read HC's, they detect O2 changes. A misifre actually causes a "lean" reading from the O2s from the unspent air entering the exhaust.

Check over the engine wiring harness. Those were bad about the insulation flaking off. There was a campain on them (silent recall) that is now expired on your car. The harness insulations would flake off and ground and short out wiring. You might have the injector harness grounding, locking open injectors causing your misfire and rich codes.
 
B

BigD

Guest
Ford changed out all the underhood wiring a few years back under a national recall program. Plugs are Autolites double plats. I need a scope because I also had a bug with an F-150 with bad coil and insulators. OBDII software never caught it but it had a miss.
Whatever it is it goes away after 10 minutes or so of running.
 
B

BigD

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I've had dirty mass air flow make it act up but never a miss. The codes are rich bank one and two. Any ideas?
 
B

BigD

Guest
I found the problem - a bad coil pack. Second one in a year too. No more Wells brand or O'Reilly brand coils for me.
 
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