m002922
OBS Enthusiast
At my wits end on this . . . if anyone has any ideas let me know. Trying not to fire the parts cannon at this . . . most of whats been done below was just previous preventative maintenance that thereby rules out those possible issues.
I'm getting a misfire cylinder 4 check engine light that generally trips between 55-60 MPH as a I get on the highway and am accelerating (into the gas, but not to the floor). I get a blinking check engine light with pretty serious stuttering . . . then the check engine light goes on solid. I get the cylinder 4 misfire code.
I've read through this thread (though different symptoms): https://www.gmt400.com/threads/misfire-issue.35866/
And I'll use this as kind of a checklist of what I've looked at . . .
https://www.2carpros.com/articles/engine-misfires-or-runs-rough
The engine is totally stock.
The engine does have a knock which I believe is the a rod bearing (based off of oil sample tests and the sound) - the engine has good oil pressure though, and it gets quieter when the engine warms up. Admittedly, on a cold Florida morning (40s) it sounds pretty awful, but at this point I'm just seeing how long it will go. The odometer (though I'm a bit skeptical) has 96k miles on it.
The truck seems to idle fine, it doesn't seem like it's "perfect" - but it's not bad either. The idle doesn't set off the check engine light.
The CEL is consistently cylinder 4 (it's tripped and I've reset it 5-10 times as I've tried different things), though today it threw a cylinder 8, I double checked that plug wire after the work I had done, I reset it, and then I got the CEL back immediately (on highway acceleration) at cylinder 4.
The last three times its thrown the code was with premium gas in it.
After looking at the timing readings with a Torque OBDII Phone App (it did seem like timing was moving around a lot - but I'm not exactly sure what normal looks like) I tried pulling the knock sensor to see if the engine knock was triggering the engine to pull timing - if memory serves even with that pulled the engine did the same thing, so I put it back in.
Plug 4 looks fine - not oily or wet. I've swapped plug 2 with 4, same issue with cylinder 4. I've swapped plug wires (2 to 4), same issue with 4. I've checked all wire connections at the cap and rotor and the plugs. I've swapped cap and rotors.
Fuel pump and spider injection are new. Compression is good. MAF checks good - I cleaned it not too long ago and it responds appropriately with throttle. I've pulled the valve cover and both the intake and exhaust valves seeming to actuate fully on cylinder 4 (I checked by turning it by hand so I could get a good look), and I adjusted them to 1 full turn past tapping with the engine running. Good oil flow up all the pushrods on the even cylinder bank.
(Sidenote, on the odd side of the engine one of the pushrods shoots oil out of it - like hitting the firewall - I did some googling on it and while odd, it didn't seem problematic or dangerous, so I didn't worry about it).
The lower intake manifold gaskets were done about 2 years ago now (with the heavy fel pros) and I don't see any evidence of an issue there. Cat converters were replaced a few months ago (I was getting cat converter CELs that have not come back with the new cats - which I suspect were ruined either by age of by the fact that I drove around with bad lower intake gaskets for some time) with 3 of 4 new O2 sensors (the new are all Bosch, it appears the remaining old one is as well).
I haven't had the truck on a highway trip since this started happening consistently, but it seems to be intermittent on the highway once I'm up to 55-60 in 3rd (accelerating) or 4th. Under part throttle no load the miss either isn't there, or I just can't tell it's there.
The one thing I haven't done is check grounds . . . but given that it is focused on Cylinder 4, I'm not sure if it makes sense to do that or not.
The Coil and the little chip next to the coil (which name escapes me) are new. The Distributor is a new Cardone unit and seems fine.
If you have any ideas let me know.
Really appreciate this forum. I used all the threads on the different cams to put together my shopping list for when this engine goes . . . appreciate everyone's input.
I'm getting a misfire cylinder 4 check engine light that generally trips between 55-60 MPH as a I get on the highway and am accelerating (into the gas, but not to the floor). I get a blinking check engine light with pretty serious stuttering . . . then the check engine light goes on solid. I get the cylinder 4 misfire code.
I've read through this thread (though different symptoms): https://www.gmt400.com/threads/misfire-issue.35866/
And I'll use this as kind of a checklist of what I've looked at . . .
https://www.2carpros.com/articles/engine-misfires-or-runs-rough
The engine is totally stock.
The engine does have a knock which I believe is the a rod bearing (based off of oil sample tests and the sound) - the engine has good oil pressure though, and it gets quieter when the engine warms up. Admittedly, on a cold Florida morning (40s) it sounds pretty awful, but at this point I'm just seeing how long it will go. The odometer (though I'm a bit skeptical) has 96k miles on it.
The truck seems to idle fine, it doesn't seem like it's "perfect" - but it's not bad either. The idle doesn't set off the check engine light.
The CEL is consistently cylinder 4 (it's tripped and I've reset it 5-10 times as I've tried different things), though today it threw a cylinder 8, I double checked that plug wire after the work I had done, I reset it, and then I got the CEL back immediately (on highway acceleration) at cylinder 4.
The last three times its thrown the code was with premium gas in it.
After looking at the timing readings with a Torque OBDII Phone App (it did seem like timing was moving around a lot - but I'm not exactly sure what normal looks like) I tried pulling the knock sensor to see if the engine knock was triggering the engine to pull timing - if memory serves even with that pulled the engine did the same thing, so I put it back in.
Plug 4 looks fine - not oily or wet. I've swapped plug 2 with 4, same issue with cylinder 4. I've swapped plug wires (2 to 4), same issue with 4. I've checked all wire connections at the cap and rotor and the plugs. I've swapped cap and rotors.
Fuel pump and spider injection are new. Compression is good. MAF checks good - I cleaned it not too long ago and it responds appropriately with throttle. I've pulled the valve cover and both the intake and exhaust valves seeming to actuate fully on cylinder 4 (I checked by turning it by hand so I could get a good look), and I adjusted them to 1 full turn past tapping with the engine running. Good oil flow up all the pushrods on the even cylinder bank.
(Sidenote, on the odd side of the engine one of the pushrods shoots oil out of it - like hitting the firewall - I did some googling on it and while odd, it didn't seem problematic or dangerous, so I didn't worry about it).
The lower intake manifold gaskets were done about 2 years ago now (with the heavy fel pros) and I don't see any evidence of an issue there. Cat converters were replaced a few months ago (I was getting cat converter CELs that have not come back with the new cats - which I suspect were ruined either by age of by the fact that I drove around with bad lower intake gaskets for some time) with 3 of 4 new O2 sensors (the new are all Bosch, it appears the remaining old one is as well).
I haven't had the truck on a highway trip since this started happening consistently, but it seems to be intermittent on the highway once I'm up to 55-60 in 3rd (accelerating) or 4th. Under part throttle no load the miss either isn't there, or I just can't tell it's there.
The one thing I haven't done is check grounds . . . but given that it is focused on Cylinder 4, I'm not sure if it makes sense to do that or not.
The Coil and the little chip next to the coil (which name escapes me) are new. The Distributor is a new Cardone unit and seems fine.
If you have any ideas let me know.
Really appreciate this forum. I used all the threads on the different cams to put together my shopping list for when this engine goes . . . appreciate everyone's input.
