Yup I agree, ground straps are important, so good idea to have replaced it.

 

Three of the coilpack connector wires will be hot with B+12vdc at KOEO, the other three wires are the primary return/ground wires going back to the computer ground switching drivers, that the computer uses to turn the primary windings on & off to create spark. If the driver for the 1&5 coil is high resistance to ground, it'll cause a wimpy spark. Same if B+12 volts to the 1&5 primary is low & its easy to check at the coilpack electrical connector.

I like g_k50's idea to check for exhaust gas in the coolant if you come to suspect a bad head or exhaust manifold gasket.

Keep us posted on your trouble shoot.

 

Pawpaw, I am probably misunderstanding you again. I only have one connector plugged into my coil pack and it only has four small wires. The only other wires are the 6 spark plug wires. I'm sure you don't mean to probe those. If I knew how to post a photograph of my coil pack I would.

 

R/LG
Dan, I think the problem is with me & my oldy moldy mind!!!!

One of the three wires is likely the B+ feed for the coilpack & the other 3 are likely the primary ground/return wires going back to the computer ground switching drivers.

SO, my Haynes manual shows the R/LG wire is the B+ feed To the coilpack & is common & splits off internally inside the coilpack, to feed all three coils primary windings start/primary wire & the other three Y/B, Y/R, Y/W, are the primary/finish wires for each coil, going back to the computer to be ground switched by the drivers.

So the R/LG = Red with light green stripe color wire, is the 12 volt B+ feed, that's hot when the ignition is on.
Seeing as how the other two coils are firing ok, the 12 volt feed to the coilpack is likely ok, but where that feed splits off internally to feed each coil primary winding could be bad, but the coil pack is sealed, so we can't get in there to check that 1/5 connection. But we can measure each coils primary resistance with a multimeter, to see if the 1/5 primary resistance is different than the other two, as that would tattle if internal connections or wiring is bad.

So you'd measure resistance between the coilpack contact where the coilpack electrical connector R/LG wire connects, individually to each of the other 3 (Y/B, Y/R, Y/W coilpack wire contacts.

The primary winding resistance isn't specified, but should be low, like maybe 5-7 ohms, or less. If the 1/5 primary measures higher then its suspect.

If the coilpack B+ measures ok & the primary resistance looks ok, then look to a high resistance problem in the 1/5 ground wire at the computer firewall connection, or maybe an internal high resistance problem in the computer 1/5 coil solid state ground switching driver, as high resistance in the switched ground circuit will make for a wimpy spark. They're known to go bad. Had one recently go bad in my 94 Taurus computer. Keep us posted on how it goes.

 

I believe that I have two issues here, with the head gaskets being the most pressing so that one is going to be addressed first. I have yet another very accomplished mechanic friend who has agreed to help me (actually I will be helping him). We are going to do the work right in my own garage on Saturdays. I am in no hurry at all as I have a car issued to me for work and my wife and I share three other vehicles on top of that. This way I can pay as I go rather than be hit with a big bill all at once. I will address the yellow spark issue if it proves to actually be a problem. It seemed to run very well between bouts with the head gasket.

 

If its leaked coolant into the exhaust side, that coolant can take out the O2 sensors. Had that happen after the Dealer replaced my head gaskets on a warranty job & got some coolant into the exhaust.

So if your scantool will monitor O2 sensors, after the head job, have it look at both banks upstream O2 sensors switching range & speed. One of mine was slow to switch & its range/voltage swing, was wimpy & it lit the CEL after a 4mile drive. So upstream O2 sensor replacement became part of the job for them.

I had developed a coolant sipping problem on the new crate engine they had just installed in 99 on my brand new one month old 4.0L. Then it took the Dealer & Factory 3 years, new heads on the new crate engine & three sets of head gaskets, the last of which were labeled on the work order as "revised", to finally stop my coolant sipping problem in the fall of 02. So take your time, make sure the heads & block are flat & use good quality head & manifold gaskets. Ford, or Felpro gaskets are of good quality & worthy of consideration.

 

Thank you for the advice, we will most definitely take our time. CarQuest handles Felpro gaskets and while we are right there and have it litterally in our hands, I will be replacing the cracked manifold as well. CarQuest sells Doorman products in that line, which are lifetime warranty. I will also be getting new head bolts. There is a local machine shop that does good work who I will be using to check the heads for cracks and square them up. They will check and re-seat the valves for me as well. The owner of that shop told me that those engines are known for the heads to crack around the exhaust valves. He agreed with me that the 2.9 is much worse than the 3.0 in that respect. He is suggesting that I stay away from re manufactured parts if I need a head. He can get new ones for about $280.00 each.

 

The heads were removed yesterday and all went very well. I did see evidence that coolant was leaking from under the head and down the side of the block in the area of the oil filter, which is located under #5. The fire ring did not appear to be blown out. The heads will be taken to the machine shop to be checked for cracks and machined. I did a compression test on all of the cylinders before we tore it down. The range was 145 to 170 (#5 was still at 150). The only thing that bothers me is that I didn't see that my left exhaust manifold had any obvious cracks and the gaskets were not blown out. I checked the EGR tube very close too and couldn't find any problems there either. It has had a very distinct exhaust leak towards the front on the left side that pretty much goes away after the engine warms up. I may take the manifold with me to the machine shop to see if they can find a crack. Due to an upcoming hunting season, its going to be another two to three weeks before I can get back to this job.

 

Finally, Success at last! The engine miss was a bad fuel injector after all. I had quite a sick feeling when I fired it up with the new head gaskets and it was still missing. The only injector that I couldn't see or reach with my stethoscope was #5. The head gaskets did need to be replaced so I don't feel bad about spending the money. While it was all looking me right in the face, I replaced the water pump and thermostat as well. I had the heads resurfaced, the valves reseated and the exhaust manifolds squared up. A cracked exhaust manifold wasn't the source of the exhaust leak, that turned out to be a very small pin hole in the EGR tube. Fresh motor oil and a new filter topped the job off. I wonder just how many miles I will be able to get on the old girl? Thanks everyone for all of your input and help.

 

OK, good find, fix & feedback on the faulty fuel injector. Was it #5, the one you were having trouble getting at????

 

Yes, it was #5. That one is under the upper intake and completely hidden from view. There was no way that I could find to listen to it with my stethoscope. I can see #6 with a mirror from the back and #4 can be seen from the front.

 

Ahhhh wouldn't you know it, Murphy's Law strikes again!!!! Well good to hear you stuck with it, ran the problem down, found the root cause & put it right. With all of the maintenance & repairs, hopefully the Ranger will likely be good to go for another long run.