Missfire cyl 5 and 2

[Jackthewack]

Hey all. I have owned the truck almost a year now and have 253k. I changed the plugs and wires both ngk. I have a new fuel pump denso about 3k ago. The truck started to have a hard start issue where it would spin over for a while befor starting and then just recently it started to set missfire codes for cyl 5 and 2. The check light flashes sometimes but only a few times and then stays solid. I cleaned the maf and the throttle body i got the injectors redone by witchhunter performance. I swaped the coils but the miss stays on5 and 2. I was going to change my timing belt soon but dont want to spend money on that when the truck is running bad. The miss is almost unfelt bit seems to get slightly worse every week (week 3 right now). The issue seemed to be intermittent at the start but is mpre frequent now. What should i check?
The fuel pump was changed and the truck had the starting issue befor i changed it but no missfires. The pump actually failed and thats why i chanfed it and the hard start stoped happening for a month after the install. The hard start also stoped for a week after the injectors and the miss stoped for a few days.
Any advice is appreciated thank you. Also some times i drive 15 miles (work comute 1 way) and it has no issues at all runs great check light even turns off sometimes.

 

[thecole1098]

Is the hard start only when the engine was cold? Also have you been losing coolant lately? I don't know if it would help too much, but I would change out the fuel filter if you haven't already.

 

[Jackthewack]

i have a new filter and coolant doesnt appear to have gone down at all. it started out olnly doing it if i let it sit for a few hours but seems to improve if i let it sit longer. if i drive it shut it off and try and restart it starts right up no issue. i am thinking about doing a compression test tomorrow

 

[thecole1098]

that's a good idea. Doing a compression test can tell you a lot about the engine. Keep us updated.

 

[phattyduck]

2 and 5 share a coil, so I would keep investigating down that route. Maybe a wiring fault to the coil?

-Charlie

 

[LookAtThatDog]

Def the coil. Swap two of them to see if the problem changes. Or just get a replacement - used or new would be ok

 

[Jackthewack]

Compression test: cyl 1. 165 psi cyl 3. 165psi cyl 5. 150psi cyl 2. 140psi cyl 4. 140psi cyl 6. 145psi

 

[Jackthewack]

I swaped the coils alread and nothing changed. I am checking the ignitor next i have 2 runners so im gona swap with the other one

 

[thecole1098]

Your entire left bank of cylinders look to be a bit low when comparing to the others, which is pretty healthy. Was that the order you did the test?

It's a long shot, but make sure that where the ignitor attaches to the body has a clean surface and that the screws are clean as well. That's how that ignitor gets its ground.

 

[Jackthewack]

Yes i tested bank 1 first and then bank 2 bank 2 was lower than i would like. I will check that igniter ground out and maybe swap it at the same time. Thanks

 

[thecole1098]

It's possible that bank was lower just simply because the battery may have been starting to get weaker as you progressed through the test, unless you had it hooked up to a charger through it. Also I aim for about 5 cranks per cylinder.

 

[Jackthewack]

I thibk i was doing roughly 4 to 5 cranks and it was on a charger. I did notice that cylender 4 was a little wet inside i really didnt like that but no miss on that cylinder. I will try the igniter tomorrow maybe

 

[Jackthewack]

I couldnt help it and i swaped the ignitor from my 2000 to my 98 so tomorrow morning i should see if it changed or not.

 

[Jackthewack]

Well its still missing this morning so the ignitor was not the culprit. Im thinking either a wire or maybe a valvetrain. If a cam gear jumped or something wouldnt it make it miss on multiple cylinders? Or maybe just run bad all together? Its like it runs fine sometimes and others its bad. Maybe a valve is sticking on cylender 5 and 2. Idk i will pull back the timing cover and just make sure the belt is timed right then ill have to pull a valve cover and see if i see any issues

 

[thecole1098]

You’d have low compression across all cylinders if the timing was retarded and it would have no balls. It is possible only one can jumped though

 

[4Reak Show]

Only thing common between 2&5 is the ignition side. So if it's not the coil itself, it could be coil control wiring which in general isn't common besides not fully seating the connector. Next thing is a spark plug on EITHER 2 or 5 will cause a misfire on both. Reason being: path of least resistance, ALWAYS. So if 2 or 5 plug is cracked, the spark will always fire out the crack on both cylinder cycles.

Long way of saying to check the spark plugs or switch one at a time.

Also, lets confirm you're on the correct cylinders. My info says passenger side is 1-3-5, driver is 2-4-6 front to back. Hope this helps.

And yes, cam out of time would affect all one bank, not just one cylinder. Again, common ground is ignition system so exhaust that first.

 

[Jackthewack]

I swaped the plugs around to no avail. I also used a spark tester and it had pleanty of spark i think this could just be 2 different issues. And thats the order of cylenders that i am following as well.

 

[LookAtThatDog]

I had a spark plug boot that was grounding to the block and inhibiting spark, giving me a misfire.

I think spark has to be your issue. 5 and 2 are connected. Your compression check looked okay. You already addressed fuel delivery. I don't see how timing or oxygen could affect those cylinders only.

 

[Jackthewack]

Idk i have brand new pmug wires from ngk. Im almost at the point i think it could be burnt valves wtf. I ran some top engine cleaner this morning to clean caebon off the valves if they had any. Its still missing. And if i floor it (i know i shouldnt with it missing) it felt like it hit a rev limiter at 4500rpm

 

[thecole1098]

Your compression would be complete ass if you had burnt valves. Have you ruled out fuel injectors yet?