Ford escort Wagon 96 - Cylinder #3 Misfire

Xrich100 · 01-09-2010, 01:55 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, 02:05 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/vbul...d.php?t=906693

Xrich100 · 01-09-2010, 03:51 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, 03:52 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, 04:45 PM

Is that the 1.8L or 1.9L? The injector wiring differs significantly between the two models.

danielsatur · 01-09-2010, 04:45 PM

A hard 12volts isn't right, there's a 12volt short to your injector 3 wiring harness!

old_master · 01-09-2010, 08:47 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, 10:06 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, 01:27 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, 07:53 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, 08:06 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, 08:22 AM

Injector must be connected when you check for pulse.

Xrich100 · 01-10-2010, 09:34 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, 10:43 AM

Did you roll the injector to another cylinder?

old_master · 01-10-2010, 11:36 AM

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.

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