The saga with this nightmare continues 🤬
So, after having my transmission rebuilt, which I thought would also solve this bucking misfire feeling mistaking the lack of power and bucking for the torque converter going bad since I wasn’t getting any codes . turns out there’s some type of random intermittent misfire at light throttle going uphill and while under load ! Truck starts and idle smoothly occasionally the idle will lope and then smooth out on its own, but for the most part it idles normally if I step on it it will pull . I’ve searched and searched To try to narrow down the culprit and what I come up with is possibly a dropped rocker, but my engine is quiet no ticking whatsoever , a blown head gasket, but my oil is clean and my coolant level is stable. I am getting a little bit of white smoke and a little bit of moisture from my exhaust. It’s not excessive, but it’s also the middle of the winter in New York. I i’ve seen the battery come under question the battery came with the vehicle. It holds a charge it charges normally my voltage level reads correctly when driving and I don’t want to just throw a $230 battery at it especially because I’m tight from having the transmission redone, I had attempted to do the spark plugs multiple coil hold down bolt snapped . All of the hardware under the hood is rusted and seized and I’m horrified to pull the valve covers and seeing as I’m not getting any excessive noise from the head area, I’m trying to refrain from snapping one of those bolts! I zip tied the 3 ignition coils in place to prevent them from moving. Any thoughts or direction since I’m at the point of this truck having a sever negative impact on my life ! Truck is cherry frame is clean and truck looks great putting aside the fact I can’t afford to replace it at the moment ! I had replaced the PCM because the original PCM was not putting out a pulse for the Evap solenoid just felt I should mention that

 

So did you actually replace any plugs? I would start by inspecting all the plugs, gap over .060" replace em under 60 you could try regapping, but honestly i just replace them if they have any age at all. While the plugs are out do a compression/leak down test. My 4.7 blew the gasket between cylinders, so no coolant loss, but also no compression on 2 cylinders. Of course I had a very definite misfire also, all the time. Lastly if the engine has quite a few miles on and has never been opened up timing set could be showing its age. Might be time for new timing chains, guides and tensioners.

Sucks having bolts break, but if you cant repair you not going to drive it soon anyway

 

so I did pull three plugs on the three ignition coil hold down that broke all three plugs were perfect the previous owner told me the truck had a tuneup done last year, but I wanted to make sure he wasn’t full of ****. He wasn’t the plugs were clean . I can’t afford to keep throwing money at it and without any definitive codes I feel like that’s what I’m doing. I was thinking about swapping my old PCM back in as for the compression test I do have a tester. My concern is if I snap the remaining coil holddown bolts will I be able to drive it without replacing them until the spring so I can recoup a little bit ? I’ve read the ignition coils ground via contact but when I researcher further I find the opposite some say yes others say no

 

What plugs are in there? How old are your O2 sensors? Might try unplugging the front O2 sensors, and see if the problem goes away.

 

I guess I'm not 100% on the coils, they have a wire in and out i assume this supplies the trigger and then the ground goes through the spark plug creating the spark. I would not think the mounting location needs to be grounded

 

then it’s safe to say if they’re loose as long as they can’t lose contact with the plug, I shouldn’t have a misfire so I guess I’m doing a compression test today in 15° of FK me 🙄 fantastic well let’s see what’s on the menu 😠

 

Low compression would give a consistent misfire. I think you have something else going on. If it only misfires under steady state cruise, or light acceleration, but, goes away if you step harder on the gas..... I would look real hard at the O2 sensors first.

 

[QUOTE=HeyYou;3601598]Low compression would give a consistent misfire. I think you have something else going on. If it only misfires under steady state cruise, or light acceleration, but, goes away if you step harder on the gas..... I would look real hard at the O2 sensors first.

Only 2 o2 sensors but the rear bank is different than the front bank and it appears that they spliced the connection as though they had the wrong O2 sensor and they rewired it to make it work. I’m just surprised that it wouldn’t throw a code if if it was an O2 sensor.

 

also you mentioned disconnecting the sensors ? So if i disconnected the sensor that won’t cause another issue if it is infact the sensor the problem will cease ?

 

Disconnecting the sensor WILL set a code, but, aside from that, no other issues. The PCM won't have feedback from the sensor to adjust mixture ratio, so, it will just run off of tables programmed into the PCM, which tend to be a tad rich.....

O2 sensors have a variety of failure modes that won't set a code. Mainly because the PCM doesn't know that it is getting bad data..... It has nothing to compare it to. A lazy O2, or one that isn't quite accurate, can give you an overly rich, or lean... mixture, which can lead to misfires. At larger throttle openings, the PCM ignores the O2 sensor anyway..... thus, the problem goes away if you step on the gas harder. (if the problem IS related to the O2 sensor.) The fact that the front sensor is spliced into the wiring harness, is NOT real confidence inspiring.