3FE runs rough, just rebuilt.

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9

91lcruiser

Joined
May 7, 2016
Threads
2
Messages
10
Location
colorado
I have a 1991 cruiser with the 3FE engine. It has just over 60k miles on it. The previous owner had over heated it badly. I took it all apart and found blown head gasket and a few of the pistons were starting to melt from over heat. I put all new pistons and rings in and all new gaskets of course. Also installed new 4 hole bosh injectors with the jumper harness. Now I start it and it runs rough, in neutral at low idle i can just barely hear a miss, but once I put it into gear(forward or reverse) it gets much worse. It'll drive, but not very well. I have readjusted the valves when the engine was hot and set them pretty tight which is possibly the problem? I just checked compression and it was way low, in the 50 psi range for most of the cylinders. I thought that since they were all that low that maybe I adjusted all the valves on the wrong TDC, but I have it turned to TDC #6 right now and the number 6 valves are loose and ready to be adjusted as they should be. I can unplug the #2 spark plug wire and the engine runs the same, so I figured it might be bad wires so I replaced those but still the same. Checked for spark with the plug out of the hole and I am getting plenty of it. Then I checked to make sure that my injector was plugged in and it was. I even switched the plugs for one and two injectors just to make sure that my wires werent bad, and it effected the engine each time I unplugged and plugged them back in, so my wires are fine.
Any thoughts or help would be awesome, I have the valve cover off right now going to check into my valves some more...
 
Sounds like you are chasing your tail on this one. Your problem is your compression, you need to tackle that problem first. Valves sounds like a good starting point. How long has this engine been running? did it run well at first and then start giving you problems?
 
When you had the head off, did you check the top of the block with a straight edge to make sure it wasn't warped? Did you have the head checked by a machine shop to make sure all the valves were sealing properly? You need to find the source of the low compression instead of spending your time messing with spark plugs and injectors.
 
Its only been running for a few days, and I haven't driven it more that a few blocks. Its been running like this ever since I rebuilt it and first started it.
I checked both the block and the head to make sure that they weren't warped. I just checked the compression tonight so that is the way that Im headed now. I did not send the head in to have it checked over, I just cleaned it up my self. I did not remove the valves to check them
 
Ok, i will try doing that in the morning then. Im just really hoping that I dont have any issues with my rings.
 
91lcruiser said:
Ok, i will try doing that in the morning then. Im just really hoping that I dont have any issues with my rings.
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Put a shot of motor oil in each spark plug hole. If the compression increases you know it's the rings. If it doesn't change you know it's in the head/valves.
 
So I made a mistake, I was running the engine while doing the compression tests on each cylinder, and my amazing compression gauge from harbor freight was not keeping up. I unplugged the main distributor wire and then tested compression and it is within specs. I also took off the intake and removed the injectors and tested them one by one with a 9 volt battery and made sure that they were firing and they were. Put everything back together and still #2 cylinder is not firing. It is getting spark. I have a new distributor cap on and a new rotor as well as new plugs and wires as mentioned before. Next I checked to make sure that all the valves were opening and closing while cranking the engine with the valve cover off. Everything looked good there. The distributor cap can only go on one way. I tried changing the timing while running, but still the miss would not go away. I am stumped, any more help would be greatly appreciated!!! Any bad sensors that could be making it miss like this and only in cylinder #2?? I know that the injector wires are good. Help please! I want to get this dang thing running good today!
 
Sorry, I did not explain it very well in my first post. I can unplug #2 spark plug wire while the engine is running and there is no change, but I do have spark. I can also unplug #2 injector wiring and there is no change in the engine. But I know that the injector wiring is fine because I can unplug #1 and 2 injector wiring while running and the engine runs terrible( missing on two cylinders now) and then I can plug #2 wire into #1 injector and the engine will pick back up again and run decent (only missing on one cylinder). I tried switching the wiring around for 1 and 2 injectors, but it still has a miss on #2 cylinder.
 
So if cyl #2 valves are opening and closing as they should, which you verified visually while cranking the engine over, then it can only be a bad spark plug or a bad injector. Testing the plug is easy, just reverse #1 and #2 spark plugs and see if cyl #2 is still the one misfiring. If so, then it sure seems like it must be the injector then, even though you tested them with a battery. Maybe some dirt or other crap got stuck in the injector and even though the solenoid valve is opening no fuel is getting by.

As Jon Held says, the 3FE fires 2 banks of 3 injectors. In other words the injectors for cylinders 1, 2, and 3 fire at the same time, and the injectors for cylinders 4, 5, and 6 fire at the same time.

If you're going to take the injector rail off again you might consider sending your injectors out for service. There's a couple of places that folks here have used with good results. One is WitchHunter Performance (www.witchhunter.com) and the other is a place in Texas whose name I don't recall just now but I'm sure would pop up if you did a little searching. They will rebuild the injectors and flow test them before and after so you'll know for sure they are working correctly.
 
The plugs are fine, they are brand new and I've also had the plug out of the cylinder with it running and I can see the spark. The injectors got swapped around when I took them out to check them out, and they are brand new so the shouldn't need cleaning, and when they were out I put a little fuel in the top and connected to a battery and the are sending fuel through them just fine. They are 4 hole injectors so you can easily see the fuel going through them. I don't think it's an air intake hose since the engine doesn't changet when I unplug number 2 cylinder, but I will definitely check that out when I get home! I will try switching plugs too just to make sure
 
What's the compression on #2 in comparison to the rest?
Is plug #2 fully seated in the head?
Does plug #2 have crush washers?

You either have no/poor compression on #2, no spark, or no fuel.
Recheck valve clearances. Swap plugs. Swap injectors.

Intake hose giveaway: if the engine smooths out above idle, but idles rough. A severe tear can cause it to stall.
 
Compression is about the same throughout, #2 is at 125. I swapped plugs and tightened them down and still no change. Rechecked my valives and they are good. Intake hose is good, no cracks at all. I have not swapped injectors again yet. I just read the codes on it and there is code 41 for the tps. Could this possibly be causing the issue?
 
Still running rough and missing on #2. I removed the intake and and the exhaust manifold for #1-3 cylinders. In #2 it was wet on both the exhaust and intake ports which would make you think that it is not firing or losing spark somewhere. So I put it all back together and ran it in the dark, and could not see anywhere where it was losing spark. I can unplug the #2 plug wire while its running and hear it sparking. I can also have it unplugged and have the spark plug plugged into the wire and see it making spark. I have switched plug and wires as well and still no change. The engine still does not change at all when I unplug the #2 wire when its running. I have ran out of things that I can think of that are wrong with it. I need help please!!!!!!!!!!!!! Could this be related to the TPS code? The check engine light is off when the engine is running, doesnt flash at all, only when I connect the two plugs in the diagnostic port.
 
I get over 125psi compression in #2, and im getting fuel, it was wet in there when I had the exhaust manifold off. The valves should be sealing good enough if im getting that much compression right? I looked in at the valves and rolled the engine over and when the valves were closed I could see small bubbles indicating that there was compression in the cylinder, and there was not a perfect seal on the valves, but should be enough to build compression and ignite I would think? Since I am getting 125 psi after just a few cranks of the engine. I just had the injectors out and tested them again with a 9 volt battery, and I can see the spray pattern, they arent clogged at all, working fine. I also cleaned out the fuel rail just to make sure. There is nothing electronic that could cause this right?? It pretty much has to be either spark fuel or compression? Could my coil be sending the spark at the wrong time for some reason? Could the engine be that far out of time?
 
91lcruiser said:
I get over 125psi compression in #2, and im getting fuel, it was wet in there when I had the exhaust manifold off. The valves should be sealing good enough if im getting that much compression right? I looked in at the valves and rolled the engine over and when the valves were closed I could see small bubbles indicating that there was compression in the cylinder, and there was not a perfect seal on the valves, but should be enough to build compression and ignite I would think? Since I am getting 125 psi after just a few cranks of the engine. I just had the injectors out and tested them again with a 9 volt battery, and I can see the spray pattern, they arent clogged at all, working fine. I also cleaned out the fuel rail just to make sure. There is nothing electronic that could cause this right?? It pretty much has to be either spark fuel or compression? Could my coil be sending the spark at the wrong time for some reason? Could the engine be that far out of time?
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Did you ever find out the issue? I'm having the same issues with my 92 but mine is on the 1 and 2 cylinders I've done new wires, spark plugs, and a new ignition coil as well. and other tasks and I cannot seem to get it fixed
 
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