When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
If you come to think #6 lifter is mucked up, was it making any untoward / unusual or intermittent noise, when you had a listen with your stethoscope as suggested earlier?
If you believe lifter deposits might be the problem, maybe before a tear down try a #6 cyl piston soak, a Techron Concentrate Plus treatment in the gas & then a good high mileage oil change, to see if the additional detergents in the Techron & high mileage oil recipe can tidy things up enough to clear the problem. Seeing as how your plug read on the other cyls seemed normal, maybe their injectors & lifters aren't mucked up too much, so the high mileage oil might be able to save a tear down. If it doesn't, Then you can tear into this puppy at your leisure.
Forgot to post my take on your question about how you could have a negative fuel trim number. It's just indicating the computer is subtracting / correcting fuel trim, because that banks O2 sensor has detected a over fueling condition / too much fuel in the exhaust, so to try & keep fuel trim as close to the ideal 14.7/1 ratio, the system took away some injector squirt time on the next cycle & measured again to see how things went with its last correction.
If we have an acting out fuel injector, or intake valve, or fuel pump pressure regulator, it can muck fuel trim up enough to confuse the computer for a bit, but the plot & a plug deposit read can help us zero in on a problem, so good idea to have posted up the fuel trim plot..
A Positive number says its having to Add fuel to correct for a lean condition the O2 sensor has detected in the exhaust. It's normal for it to vary from 0 to +/- 5%. Fresh O2 sensors & new fuel injectors, in a engine with good compression, might keep fuel trim between +/- 3 %.
Your plot seems to indicate you have an intermittent problem mucking up fuel trim & your mucked up #6 spark plug suggests the problem is with that cylinder, question is what is the root cause?
If on your stethoscope listen scenario you heard unusual valve, or fuel injector noises compared to the other cylinders which Don't seem to have a problem, then you know maybe a intake lifter, or fuel injector, or stuck oil control ring belong on the suspect list.
More thoughts for consideration, will be interesting to hear what you find & how it goes.
Pawpaw, thanks for all your help. I ordered a cheap borescope. I figure a $40 tool is less than a seal set if the head does not need to be removed. If it does need to come off, at least then I know for sure. I will post the results when it arrives on Wednesday.
Finally got pictures this morning. I had to wait until I could borrow my wife's phone to take the images. The piston is sooty. I could not get a good picture of the valves inside the cylinder, but I was able to get some good pictures of the top of the valve. There is some discoloration on the top of the #6 intake. I checked the #5 for comparison, and it is much cleaner. Below are the images i took.
Cylinder with Piston near top. Top of piston Cylinder wall. Note the cross hatches still look good Top of piston with piston down Another shot of the cylinder wall Top of #5 valve Top of #6 intake valve Another shot of the top of #6 intake valve Different shot of#6 intake.
Took the heads off yesterday. #6 was very dirty and sooty. Definitely getting oil into the cylinder. It also looks like I had a small leak in the head gasket on the #6 cylinder and a small leak in the #6 exhaust seal. #5 is apparently also having some trouble that did not show up on the plug. The plug looked ok on #5, but the cylinder and head are a a dark brown instead of white like the rest. There was also a tiny bit of carbon on the exhaust of the #4, but it generally looked good. The bank 1 head looked as it was supposed to. I currently have the heads at a local shop for a cleaning, check, and replace the valve seals. I figured have them both done at the same time so they will hopefully wear evenly. I will post some pictures of the cylinder. Is there a good way to check the rings at this stage? I do not want to put it back together only to find it was a piston ring. Also, is it possible to replace the rings without pulling the block out of the frame? I do not have access to a hoist. I have seen people which say it is possible to remove the oil pan without removing the block, but they give no details.
The only "systematic" piston-related problem I've ever heard/read about regarding the Ford Cologne 4.0L OHV engine has to do with the "wrist pins" causing a marbling sound resulting from some engine teaks for the '98 MY. (FWIW, my '98 4.0L w/208K + miles has always made that sound). Conversely, I don't ever recall ever hearing/reading about any piston ring problems with the motor.
It does seem that that the 4.0L push rod ends are susceptible to wear and tear and so you might want to consider that when you put it back together. See generally: https://www.therangerstation.com/how...0l-pushrod-v6/
ON EDIT: For some reason, when I click the TRS link that I cited directly above this sentence, it brings up the WRONG website and link. For some reason it re-directs me to a "Babcox Engine Building Magazine" website and to a link that has nothing to do with the subject at hand. Mods, what is going on with that?
Also regarding reassembly, might also find some helpful information HERE.
Well, bad news. My supposedly new heads I put on right after I got the truck were not new. The shop just called and said one of the valve seats fell out during disassembly and they appear to have many more than the 40,000 I put on them on them. I guess it serves me right for trusting ebay last time. Anyway, he predicts $550 for repair, but figures I'm better off just buying a new set. I have see this company pop up a few times in searches. https://www.kingcylinderheads.com/pr...98tm-assembled
Does anyone know if they are any good (I don't want to go back to stock as they are known to crack). Also, I am almost thinking of outright replacing the motor at this point if I can find a better one cheap enough. Any thoughts/suggestions on this?
I would call this company and talk to some one on the other end just to get a feel of these heads before you buy them. Make sure you get a real person telling you exactly what country these heads were manufactured in before you make a decision. Keep us informed.
Tried posting yesterday and apparently it didn't work. Ordered a new set of heads from EngineQuest. They seemed to have the best reputation of anyone I could find, and I just assume that all the heads for this truck are cast in china (I can't find any evidence to the contrary). EQ claims they do the machining on CNC and then do a pressure test and inspection. They also have a 2 year parts and labor warranty that seems to have fewer exceptions that other sources, so it does seem to be more trustworthy than other sources. I hope that is is correct since I don't want to do this again in another 40K. I will let you all know how it goes when I get them installed. Does anyone have thoughts on having the new set checked before installation? This company seems more reputable, but once bitten, twice shy.
What happened to cause this engine, or block to begin to eat heads?
The only Factory Rep feedback I heard back in about 01, when the Factory & Dealer were trying to unravel why my replaced under warranty for "marble noise" 99 4.0L new/long block crate engine kept sipping coolant, was that the factory rep said back then that they were having some "porous head" problems. I assumed he meant with the machined heads, but the 4.0L was a German built engine. So who knows where they were getting the heads cast back then, I never heard any info I'd take to the bank.
In my case the recurring coolant sipping on the new long block crate engine, that they replaced the heads on because it developed a coolant sipping problem, then replaced the head gaskets on that engine once, then again & was fixed the second time when the Factory issued & had the Dealer use "revised" head gaskets on the second try in Aug of 02. That finally fixed the coolant sipping problem for me.
In my 3 year saga I never heard of nor had any Mechanical head problems, like with valves, or seats, it was a coolant sealing problem, that was finally put right & remains so with the "revised" head gaskets.
Now the 3.0L Vulcan is another story when it comes to heads & valves, they don't like to be over heated or they'll warp & valve recession on the 3.0L is a problem, but I've not heard of many Mechanical problems with the 4.0L push rod engine heads.
Its been a while, but new heads are on, new push rods and rockers. All new seals and I painted the valve covers while they were off. Started it for the first time yesterday. Was a bit concerned by the noises, but it settled down after about 5 minutes of idling. I still have a bit of a tap somewhere, but I think that is one of the new rocker arms wearing in and should quiet down over time. CEL came back on with code P0102, maf malfunction. I will believe it since it has a bad hesitation and will die at idle once its warmed up. Any ideas where to start looking? I guess it could be one of my seals, but I think I have everything on there tight. I don't really want to pull the top apart too far again.
P0102 is for MAF sensor low input. So check the reference voltage to the MAF sensor at its electrical connector & if ok, maybe remove so you can get to both sides & try cleaning the sensor with CRC MAF Sensor plastic safe non residual spray cleaner. If the engine has recently been run, let the sensor cool & don't touch the sensor electrode with the spray wand. Let it dry but keep it squeaky clean when reinstalling so as not to contaminate with under hood corruption. Then let us know how it goes.
So I got the air leaks fixed after I had to pull the top apart to fix a fuel leak at the fuel pressure damper. Didn't have the pressure rail studs tight and didn't have the upper intake tight, so the air leaks are fixed. However, today I was driving and the engine died at 45mph and wouldn't restart. When I got off the road, I found power steering fluid all over. Looks like I burst a high pressure line at the pump, probably from moving the pump around when I did the heads. I also read this morning that I should have used ATF instead of power steering fluid, and that mixing the two (which I did) will cause this problem. However, the engine will not start. I think I got fluid somewhere and killed power to the PCM. Any ideas where to start looking? There is fluid all over the fuse box, and cleaning it seemed to make the relays kick on and off.
Good grief, sounds like "Murphy's Law" has found a home here!!! Hang in there, stay calm, think your moves through Before making them & sooner, or later, the problems will yield & success for all your efforts will be yours.
If the ECM is still alive, scan for trouble code clues & post up All code Numbers, as they can help focus a trouble shoot.
