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Ford escort Wagon 96 - Cylinder #3 Misfire


Xrich100
01-09-2010, 02:55 PM
Car runs very rough like its missing and then it recovers on its own for a couple days then runs very rough again. It comes in and out sometimes 5 minutes apart. Scanned computer - "cylinder 3 misfire". Pulled wire, plenty of spark - no change in engine, so this is a dead cylinder.

Then pulled connector off of #3 injector - no change.
Put voltmeter on #3 inj. connector and saw a hard 12v.
Measured a working one and saw a low but pulsing voltage.
Its sounding like to me that the ecm output for the #3 injector is bad.
Any other opinions on what it might be?

danielsatur
01-09-2010, 03:05 PM
Roll the spark plug, wire, coil, and injector to another cylinder.
An Injector can still be bad, see Fuel Injector check
http://www.automotiveforums.com/vbulletin/showthread.php?t=906693

Xrich100
01-09-2010, 04:51 PM
I replaced the wires, fuel filter, coil and the spark plugs are newer. Why would I have a hard 12volts on the connector? Shoulnt it be pulseing? Why then would it be working sometimes and not others?

Xrich100
01-09-2010, 04:52 PM
I replaced the wires, fuel filter, coil and the spark plugs are newer. Why would I have a hard 12volts on the connector? Shoulnt it be pulseing? Why then would it be working sometimes and not others?

Selectron
01-09-2010, 05:45 PM
Is that the 1.8L or 1.9L? The injector wiring differs significantly between the two models.

danielsatur
01-09-2010, 05:45 PM
A hard 12volts isn't right, there's a 12volt short to your injector 3 wiring harness!

old_master
01-09-2010, 09:47 PM
All injectors have constant battery voltage to them whenever the ignition is in the crank or run positions. The ECM supplies ground to open each injector through its own individual wire. If #3 injector shows battery voltage on both terminals, the ECM is not supplying ground to it. Look for an open circuit, (broken wire etc) from the ECM to the injector.

1.8L engine: Grey with red trace wire goes to pin #12 at ECM
1.9L engine: Brown with yellow trace wire goes to pin #74 at ECM

Xrich100
01-09-2010, 11:06 PM
Its the 1.9L engine. The voltage I read is across the connector. I read some where that the less performance coming from the cylinder the longer the on time of the injector. Im wondering if the cylinder is dead does that mean the voltage will stay on ? Which puts me back to a bad injector.

Davescort97
01-10-2010, 02:27 AM
Pull the plug on #3. If it is dry you have an injector faulty. If it is wet with gas do a compression check.

old_master
01-10-2010, 08:53 AM
While the engine is at idle, connect one probe of the DVOM to chassis ground, connect the other probe to the brown, yellow trace wire: The voltage should pulse. If it does, most likely the injector is faulty. If not, look for an open circuit in the brown yellow trace wire from the ECM to the injector. If the wire is ok, the ECM is unable to provide ground for the injector and needs to be replaced.

Xrich100
01-10-2010, 09:06 AM
Can I make that check with the cable unplugged from the injector? Thats the way I did it. Will it be pulseing even though the cylinder isnt firing. Ive read the timing of those pulses changes with performance. If the cylider isnt firing would the voltage just stay on? I get a hard 12volts across the 2 connector pins with it disconnected from the injector and engine running. Is that right? , will it just pulse when it is connected and the cylinder working? And the problem comes and goes. I know its a fuel problem I have good spark at #3.

old_master
01-10-2010, 09:22 AM
Injector must be connected when you check for pulse.

Xrich100
01-10-2010, 10:34 AM
ok just made some more checks and I have come to 2 conclusions what do you guys think?

I measured the voltages on all 4 injectors connected and engine running using a digital dvm.

On the 3 working cylinders 1,2,4 I found on the connector of the cable all the injectors connect to, a pulsing reading of .5 volts going down, which of course a dvm is too slow to see actual but that should be what i see on # 3- but Idont.

On # 3, I see 9.4 volts steady - so...

Either the ecm is not pulsing it right, or the injector is bad and the computer is compensating for no power by turning the injector on longer?

I dont know what else I can do to isolate it further without swapping ecms or injectors. Ecm is by far the easyist.

danielsatur
01-10-2010, 11:43 AM
Did you roll the injector to another cylinder?

old_master
01-10-2010, 12:36 PM
Unplug the injectors and check the resistance of each one. They should obviously be close to each other, if #3 comes up noticeably different, you found the poblem. Swapping the injectors is another possibility, but way more work than necessary. Diagnose it correctly and do the job once. Changing the injector plugs to different injectors will not work, the ECM activates them in sequence.

Xrich100
01-11-2010, 03:13 PM
I just measured about 15 ohms across all injectors. I havent swapped them because there very hard to get to and didnt want to untill i have no more choices. It doesnt even look like theres room enough to slide the fuel rail out of the intake plenum. Whats the best way to take it out?

old_master
01-11-2010, 05:03 PM
Resistance should be 12 to 16 ohms, so you're good there. Make sure the red wire at the injector has battery voltage when the ignition is in the RUN position. Unplug the injector and connect a noid light to the harness connector, then crank the engine and watch for the noid light to blink. If it blinks, suspect a faulty injector. If it doesn't blink, check the harness all the way back to the PCM.

Remove the intake plenum first, then:

1.Relieve the fuel system pressure.

2.Disconnect the negative battery cable.

3.Disconnect fuel supply and return lines using the proper tool for spring lock coupling removal.

4.Unplug the fuel injector electrical connectors.

5.Remove the two fuel injection supply manifold (fuel rail) retaining bolts.

6.Carefully disengage the fuel injection supply manifold from the fuel injectors.

7.Disconnect the vacuum line from the fuel pressure regulator and set the fuel injection supply manifold aside.

8.Grasp the fuel injectors body and pull up while gently rocking the fuel injector from side to side.

9.Once removed, inspect the fuel injector end caps and washers for signs of deterioration. Replace as required.

10.Remove the O-rings and discard. If an O-ring or end cap is missing, look in the intake manifold for the missing part.

Xrich100
01-11-2010, 06:43 PM
Can the fuel rail come out without removing the intake plenum or even take the injectors out of the rail while its inside of the plenum?

Xrich100
01-15-2010, 11:03 PM
Heres where im at with this. Replaced so far, wires,coil,ecm,fuel filter. The # 3 cylinder basically works sometimes and sometimes it doesnt. I just took compression readings - #1 130lbs , #2 130lbs , #3 185lbs , #4 160lbs also the # 3 plug was alot wetter then all the others and had to be cleaned. Drove it and still the thing cuts in and out at will. What now? Why is #3 reading so high? The injector is all that is left and there not easy to get to in this car.

danielsatur
01-15-2010, 11:29 PM
I found a good video , looking for unmetered air leaks, check the injector leak
www.youtube.com/watch?v=FfiQ7qWiG-M (http://www.youtube.com/watch?v=FfiQ7qWiG-M)

185psi #3 makes sense, because of more air to compress!
Too much Air could blow the candle out, the Air/fuel mix is off on that cylinder.

old_master
01-16-2010, 08:50 AM
An unmetered air leak would cause the cylinder to run lean and the plug would be dry. The higher compression could be caused by carbon build up from running rich on that cylinder. What brand and part # are the spark plugs? Have you tried swapping #3 plug with a different cylinder and see if the miss moves or stays on cylinder #3. Have you checked fuel pressure and leakdown? Fuel pressure must not drop more than 5psi below pump prime pressure after the pump shuts off. If it does, the #3 injector might be leaking.

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