Spark from coil problems

[holliwbase]

I have an 86 Ranger with a random intermittent miss. This truck sat for nearly 2 years because of a problem that was diagnosed as fuel pump failure. This repair was done at a shop that I have experience with in the past and I trust their work. They replaced both fuel pumps and both fuel filters but still ran into driveability issues. This wasn't a daily driver so I made it clear that putting this on the back burner was okay with me. Over the course of time some other issues cropped up and they kept trying to get if fixed. They replaced the distributor, cap and wires as well as an O2 sensor and connector that had gotten against the exhaust. Over time I could tell they really were wanting to be rid of it so I settled the bill and barely got it home. So I discovered some issues and repaired them. The EGR system was inoperable so that all was fixed. I discovered that they had not removed the spout when they timed it and I fixed that. The thermostat was stuck open, replaced that and ECT sensor and the IAT sensors also needed replacing. Corrected some vacuum leaks. Still not getting rid of this annoying miss. Decided to make sure the the fuel system was not responsible. I forgot to mention that I had picked up an 89 2.9 complete with the tranny for a really good price that the guy had pulled out of a Ranger he bought and drove for over 2 hours to get it to his house. Lot's of spare parts on hand that I knew were good. So I cleaned the injectors from both engines and actually installed the inlectors from the other engine and then tested the electrical with noid light. Then I started on the electrical. Checked every plug wire with my DVM including the coil wire they were all okay. Used my spark tester to make sure the spark was adequate on all cylinders. The ICM that came with the distributor was faulty and I had replaced it. I still tested out the new ICM as well as the one that was on the other engine they both check out ok. JUst to cover all the bases I replaced the cap and rotor that they had installed at the shop. That's when I ran into a no spark condition. Replaced that distributor with the one from the 89 and got my spark back. While retiming I noticed timing light would flicker and it corresponded with miss at idle speeds. I moved the time light over to cylinder 2 and same thing so I move it over to the coil wire and hooked up my spark tester to #2 and I got intermittent flickering of the timing light that corresponded to temporary spark loss at the spark tester. I just finished following the instructions explictly on trouble shooting the ignition system. Everything passed. I then tested the thje wiring that goes from the coil, to the ICM and to the ECM and could not find any issues in regards to continuity. Wiggled wires arounfd as best I could and didn't see any changes in resistance values. Basically, what I'm saying is I used two different coils, two different distributors, two differnt ICM's and yes I bought a different ECM as well, so two of those with no improvement in my spark loss. What should I look at next. I think the only part of the circuit not checked was wiring to and fron the inition switch. I need help. Just a little more history on the truck my Dad bought in in 1993 and it has been in the family since then. My sister had it, my brother had it, my youngest son had it and as soon as I get it fixed It will to my daughter.

 

[rusty ol ranger]

Check the plug at the coil.

The wires inside the plug like to break off inside of it. When mine did it it completly quit but its an often overlooked thing.
j
They could be messed up and not making a good connection

 

[holliwbase]

Thanks for the reply. I'll check it this morning and report back. One thing I thought about last night was the ground wire attached to the coil. I've haven't checked it out where it attaches to the frame. At this point I think it's something very basic and fundamental that is causing the problem and the coil wire and the ground certainly fall into that category. Once again, thanks for the suggestion.

 

[holliwbase]

I checked the coil wire and it is okay, got 500 ohms per inch while manipulating it from one end to the other. I did go back and check the ground path for the coil and it was terrible. However after cleaning up the bracket it bolts to and resolving the issue, verified with the multimeter I still have the spark going away and of course the higher the rpm the more negative impact it has. I literally do not know what to check or do to fix this. Out of desperation I will probably switch out the ICM that came with the other engine. I tested it according to the Chiltons manual and it was good but so waas the one that's in it. Suggestions are welcome.

 

[2011Supercab]

What do the spark plugs look like?

 

[holliwbase]

I just replaced them. They have less than 50 miles on them so I haven't looked at them.

 

[rusty ol ranger]

I checked the coil wire and it is okay, got 500 ohms per inch while manipulating it from one end to the other. I did go back and check the ground path for the coil and it was terrible. However after cleaning up the bracket it bolts to and resolving the issue, verified with the multimeter I still have the spark going away and of course the higher the rpm the more negative impact it has. I literally do not know what to check or do to fix this. Out of desperation I will probably switch out the ICM that came with the other engine. I tested it according to the Chiltons manual and it was good but so waas the one that's in it. Suggestions are welcome.

What color is the ICM?

If its black....you need grey

 

[holliwbase]

It's gray. I just finished installing the other ICM and it's warming up now. I'll be damned, my miss is gone. So the the new ICM I bought 2 months ago was faulty even though it passed all the resistance test before installing it. I think it's time for a beer.

 

[gaz]

@holliwbase ,
Hello,
You say this truck sat for a couple years. It sounds like you are aware of the history of this vehicle.

Have you changed the oil since it sat. I had a 2.9 that sat for a couple years, it started and ran while warming up and burping the fresh coolant but after a test drive it developed a misfire or a stumble.

I went through the fuel and electrical systems but could not eliminate the miss. Out of sheer process of elimination I dropped the oil. I noticed the first fluid coming out did not look like oil, then oil came out afterwards. I would not have checked the oil except for the intermittent miss; apparently they do not like water in their crankcase. The lower intake manifold gasket had been compromised, permitting coolant into the valley and subsequently, the oil pan.

In summary, it may be worth your time and the cost of an oil change to know that your oil is not contaminated.

 

[RonD]

You can't test if a Coil is good, only bad
You can't test if a spark module is good, only bad

This is because they run HOT, ".......Damn Hot, Real Hot!"
A coil or spark module can fail a test, so always good to test them, but they can not be relied on to be Good after a passing test

 

[holliwbase]

I did some more reading about the TFI and one thing I found that caught my eye was testing it for resistance is not a good way to determine if it's good. I replaced that TFI because I got a code and tests on the truck did confirm it was faulty. After I replaced it there were still other issues that cropped up that kept my attention away from looking at that new TFI as still being an issue. Seriously felt like I was playing whack a mole at times. The reason I changed it out yesterday for the the other TFI I had was that I knew everything else in the system was good, it was the only thing it could have been. In response to gaz, I'll be changing the oil today and then I'll drive it around here for a week or so just to make sure there are no other issues and then I'll turn it over to my daughter. The truck genuinely only has 87,000 mile on it and before the fuel pump went out I had completely gone through the driveline. It's in great shape. I still can't get it to initiate the self test on the EGR system and I still get a 25 code about knock sensor but I'm ignoring that since I know that the EGR system is fully functional.