3FE Discouraging tale (valves, oil galley, and knocking)

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So I want to hash out the tail of the past year from the beginning to get feedback on where you all think I should go next. I have learned a lot about this truck and this engine but I'm lost as to what is happening in my engine that is causing the problem. Thanks for all the help thus far! Big shout out to @GLTHFJ60 for laying on the ground with me and teaching me the ropes!

Bought a 91 one year ago. Very little issues really ;) just a almost complete brake rebuild, replace a leaking gas tank and filler neck and seal up a leaking sunroof!

Has far as the engine....super black oil, changed it and turned super black again within a week. So I changed it again! But it ran fine, seemed to have some power and no knocking, but the exhaust system was completely busted and providing no back pressure. First repair therefore was the exhaust, complete rebuild from the headers back. Highflows were already in place, not clogged and worked back from there with lots of increased flow with dual pipes. Shortly after this repair, we determined there was a knock in the engine, and never really saw a power gain after the repair. Finally got around to a valve adjustment and it drove great, tons of horsepower gain, it was like a new truck! The very next day oil galley plug blows out but in the driveway so I was able to catch it. This was my first repair flying solo and with some help went very well. Set screws are holding nicely (see pictures). The next time I started it up, I went to the shop to change the oil and filled it back up with the usual 10-40 with some MARVEL mystery to start loosening up all the gunk we found when doing the valve adjustment, then went to fill it up with some 93 (which I had been using to eliminate the knock) and pulling out of the station (only about 20 miles since the oil change) all the power gains from the valve adjustment went bye bye. Within another 20 minutes the engine light starts coming on whenever I accelerate and stays on for a few moments then cuts off. That night I take the battery off to reset the system and codes. Restart in the morning, first acceleration and engine light comes back on! Light pretty much stays on. Dealer pulls codes and says O2 sensor (weren't sure which) and some weird code about speed. No one had a clue, so they accidentally replace the speedo cable which had broken at some point, and say lets go back and do another valve adjustment. So Bob who has been at Fred Anderson for 25 years gives me my second valve adjustment in some 55 miles. They return it back to me yesterday and it runs amazing. All the power gains I had achieved in the first adjustment I got back! Problem solved, Bob found 4 valves were too tight. But the next day (today) I start it back up and the power is gone again!!! Super sluggish, almost no throttle response, slowly put it to the floor and the rpm gauge doesn't even move. But this time no engine light. So I drive 20 miles and stop, pull the circuit breakers for the electronic fuel injection system, wait the 15 mins. SOME power comes back for about 10 miles but more or less back to the slow stubborn unresponsive goat syndrome. Then I put a tank of 87 in there to see if the valve adjustment fixed the knock, and nope, knock is still there but not quite as bad. AT THIS POINT IM
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LIKE WHERE IS THE FOR SALE SIGN!!

And in the garage she will sit again until I have a chance to go at it....

Thoughts?!?!
 
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One last thing, after the exhaust job, found it was running ultra rich. Replaced plugs immediately and none were fowled, just normal wear. Reset EFI systwsby pulling fuse and that solved the running rich issue. Shortly after that I heard the knock, might have been there all along just didn't notice it, only can hear it under heavy load. Okay now that is everything!
 

jrmudder92

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So I have a little experience on this long story.... But I can say that when I had my 3fe the black oil was normal. Put fresh oil in it driver around the block black oil again. I just lived with it! Also the knock you are describing sounds like a spark knock. Mine also I had that. As you have found out higher octane gas helps fix that. Have you checked the timing? I would start there! I had a hard time getting it just right
 

jynx

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I agree check the timing, but the fact that it comes and goes makes that an odd one. Check the bolt that retains the distributor and make sure it isn't moving and allowing the timing to vary.

Aside from that check air filter, box and inlet piping for restriction. Check the dizzy cap and rotor for bad contacts. Outside of that, I'd say you are going to have to start troubleshooting the AFM, fuel system, etc.

Being out of time will kill power like you describe, but the variation in the loss is what's messing with me.
 
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I agree check the timing, but the fact that it comes and goes makes that an odd one. Check the bolt that retains the distributor and make sure it isn't moving and allowing the timing to vary.

Aside from that check air filter, box and inlet piping for restriction. Check the dizzy cap and rotor for bad contacts. Outside of that, I'd say you are going to have to start troubleshooting the AFM, fuel system, etc.

Being out of time will kill power like you describe, but the variation in the loss is what's messing with me.
Excellent thoughts! Yeah after the valve adjustments (both) had constant power gains but also after each the next day the power loss seems to stay constant as well. I guess only variation was this last time when I reset the EFI system. But that was slight and short lived. Thanks again guys for reading the saga!
 

lt1fire

 
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I would say almost certainly you have issues in your valve train, how do your valve guides and seals looking? My guess is they are causing a gap by letting oil sit on top of the valve.

Talk to the mechanice at the dealer but in my experience most deal mechanics aren't used to working on older vehicles and also don't spend the time to try and find out why there might be a problem they just fix it. At the very least they should do the job again of check it since they did it a day ago.

Also learn to adjust the valves yourself. If you can change oil and fix the galley plug you can certainly do that also. That way if you adjust them get the power back and then it goes away again you will know which ones needed the most adjusting the last time and also if it is the same ones this time. Since it is over a night I would guess the guides and seals are leaking and letting oil sit on top of the valve causing a gap..... happening overnight is still extremely fast for that to happen though so the problem may lie elsewhere in the valvetrain and also once you get it running right again through the valve job check the timing on it.


The black oil was fairly common in my 3fe when I got it with fairly high miles but after some seafoam in the crank 500 miles before oil change and doing the full seafoam treatment it started to stay a lighter color between changes.

The 3fe is a great motor, under powered but will chug on forever. They are also dirt simple to work on. Every year I adjusted my valves (even though they didn't need it with the small amount of miles I put on it), I also did fuel pressure checks, coolant system checks, leak down tests and compression tests twice a year. Mine ran perfect and I never really complained about lack of power even with the huge meats I was chucking around.

So i'd suggest learning the valve adjustment, or have someone in the club show you how to do it the first time, and then go from there and keep an eye on everything else.
 

little_joe

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Did you ever baseline the thing? I don't know squat about the 3FE, but baselining can eliminate a lot of variables. For example, aside from the valves and plugs, as others have said check timing, distributor; how old are plug wires? pcv? fuel filter? air filter? The simple, inexpensive maintenance things need to be done anyway, if they fix a problem, great; if not, you're eliminating variables and will be set to roll once the root cause is identified.
 
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I would say almost certainly you have issues in your valve train, how do your valve guides and seals looking? My guess is they are causing a gap by letting oil sit on top of the valve.

Talk to the mechanice at the dealer but in my experience most deal mechanics aren't used to working on older vehicles and also don't spend the time to try and find out why there might be a problem they just fix it. At the very least they should do the job again of check it since they did it a day ago.

Also learn to adjust the valves yourself. If you can change oil and fix the galley plug you can certainly do that also. That way if you adjust them get the power back and then it goes away again you will know which ones needed the most adjusting the last time and also if it is the same ones this time. Since it is over a night I would guess the guides and seals are leaking and letting oil sit on top of the valve causing a gap..... happening overnight is still extremely fast for that to happen though so the problem may lie elsewhere in the valvetrain and also once you get it running right again through the valve job check the timing on it.


The black oil was fairly common in my 3fe when I got it with fairly high miles but after some seafoam in the crank 500 miles before oil change and doing the full seafoam treatment it started to stay a lighter color between changes.

The 3fe is a great motor, under powered but will chug on forever. They are also dirt simple to work on. Every year I adjusted my valves (even though they didn't need it with the small amount of miles I put on it), I also did fuel pressure checks, coolant system checks, leak down tests and compression tests twice a year. Mine ran perfect and I never really complained about lack of power even with the huge meats I was chucking around.

So i'd suggest learning the valve adjustment, or have someone in the club show you how to do it the first time, and then go from there and keep an eye on everything else.
@GLTHFJ60 was very kind to show me how to do the first one, probably need another one supervised before im confident that i can spread my wings. The gap makes the most sense with the short time window. Thank you!
 
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I wonder if there is burnt oil on the back of the valves, choking the exhaust flow. or clogged cats. someday Evan and I will be tearing into my 92 and all this voodoo will be exposed...
 
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I wonder if there is burnt oil on the back of the valves, choking the exhaust flow. or clogged cats. someday Evan and I will be tearing into my 92 and all this voodoo will be exposed...
The line for 1 thru 3 is good 4 thru 6 looked a little richer, they bith seemed the same age when I got the truck.
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those are not original. but look rather clean. does anyone near you have a bore scope? pull the plugs and look for gunk on the back of the open exhaust valve. leaky valve seals can allow the oil to burn on the back and grow into some nastiness. I remember blasting the valves with crushed walnut shells ( leaving the heads on the engine) on a tercel that only had 17,000 miles on it. it would not surprise me if the heads on my 80 were fairly coked up at 229,000. I know that the heads were caked with baked oil 3/8s inch thick when I adjusted my valves.
 

lumbee1

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@TheWhitefox lots of good suggestions here. I don't know much about 3FE's either but I would start with the baselining recommendation from @little_joe. How much oil are you using? Any smoke on startup? Any smoke after running for a while? If there is smoke, what color is it? Replace anything you haven't already replaced or know that someone replaced recently. Diff fluid, transfer case fluid, fuel filter, air filter, plugs, blinker fluid, etc. I wish I had some free time between now and Relic Run to help you out.
 

cruisermatt

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@TheWhitefox on the bright side, I didn’t know that you could fix a rich mixture issue simply by pulling the EFI fuse. So that’s for teaching me something! Off to try that now.
 
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@TheWhitefox on the bright side, I didn’t know that you could fix a rich mixture issue simply by pulling the EFI fuse. So that’s for teaching me something! Off to try that now.
Well the thought process was, with no back pressure, that could throw off the electronics so by fixing the exhaust thus adding backnin the original pressure plus reset the system definitely solved the problem. Also fixed a leaking gas tank so that might have contributed as well!
 
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those are not original. but look rather clean. does anyone near you have a bore scope? pull the plugs and look for gunk on the back of the open exhaust valve. leaky valve seals can allow the oil to burn on the back and grow into some nastiness. I remember blasting the valves with crushed walnut shells ( leaving the heads on the engine) on a tercel that only had 17,000 miles on it. it would not surprise me if the heads on my 80 were fairly coked up at 229,000. I know that the heads were caked with baked oil 3/8s inch thick when I adjusted my valves.
Pulled and replaced plugs after the exhaust job, normal wear on all and all had the same buildup on the, no one or two worse than the others. Seemed incredibly normal which surprised us.
 

cruisermatt

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What does exhaust backpressure have to do with anything? There isn’t any sensor that takes pressure readings anywhere on the exhaust or combustion chamber.
 

GLTHFJ60

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Excessive exhaust backpresure (clogged cat or otherwise) will cause a loss of power, because the engine cannot circulate air through the engine. Instead of the pressure differential forcing air out of the cylinder on the exhaust stroke, backpressure in the system will cause the engine to retain *some* cylinder pressure after the exhaust stroke, which means less fresh air (and fuel) comes in on the intake stroke.

Very high backpressure is a bad thing.
 

cruisermatt

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Excessive exhaust backpresure (clogged cat or otherwise) will cause a loss of power, because the engine cannot circulate air through the engine. Instead of the pressure differential forcing air out of the cylinder on the exhaust stroke, backpressure in the system will cause the engine to retain *some* cylinder pressure after the exhaust stroke, which means less fresh air (and fuel) comes in on the intake stroke.

Very high backpressure is a bad thing.
You are 100% correct, what I was implying was that there aren’t any components in the 3FE EFI system that take this into acount.

Short of completely clogged cats I don’t see that being relevant to his issues.
 

Trollhole

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First thing I would do is check the EFI temp sender. Make sure it specs out. Second is I would find another ecu and give it a try.

3rd you have sludge in your motor. It's going to cause the black oil until it's all gone. Seafoam can help over a long period of time.


On the cats. Get a shop vac or leaf blower and put the tube on one side of the cat and fee your hand at the exhaust tip. Do both cats flow the same? If so is the flow fairly close to what the leaf blower or vacuum is reading? Could mean a cat is clogged or you have a restriction in the muffler. Have you tested the EGR? Also look at wire harness going through top of motor. Does moving it cause any issues?


Lastly what are your compression numbers?
 
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