YakAttack

Never figured it out. I brought it to dealer and paid for a diagnostic test there. Compression, injectors, fuel pressure, plugs, wires, coil are all fine. All they could say was it seemed like more of in internal problem causing cylinder 5 to have that dead miss. I was told find a shop with a scope that can look at the internals was an option. Removing the valve cover and valley cover under the intake and check for stuck lifter which I already removed the valve cover before I didn’t see or feel as if anything was stuck. Never took off valley cover. I could bring to shop and pay $3000 to install new lifters or I could take the heads off myself and inspect it and try diagnosing what’s wrong. I want to trade it in but with how much I owe and how much I’d get with a vehicle missing like this I def think I’d be so far upside down. So i’m left with a decision to make

Now the ANS light kicked on and the stabilitrak lights are staying on with it.

For all of those who are following the post I didn’t get a chance to bring to dealer today before it was closing but was able to get a proper compression check. It got 180 psi at cylinder 1,3,5,& 7. Still when pulling just the plug in connector on coil #5 I am not getting any difference in engine sound as I do the others. Still I am getting spark from the plug on that cylinder. So we still at the confused point.

I will end up bringing it to the dealer on Friday and let them check it out. Tell them what I done so far and observed and see what they find. The compression check he done to it on cyclinder 5. Wish he would have at least checked out another one. I don’t have a compression gauge and he is 2 hours away.

I still don’t understand why when I pull connector on cylinder 5 coil it makes no noticeable change to the engine like the other 7 do. ??

I swapped injectors. Swapped coils. Still get the same miss. I took valve covers off on both sides this morning. I took videos. All of the rocker arms are operating properly. No ticking coming from any of them

I went got the noid light and looks like all injectors checked out just fine.

I will get noid light rental from O’Rielys and check each one. How do I use the mechanic stethoscope?

It’s more of a slight tick. Not really a squeak. We haven’t tore into anything more than taking off just one valve cover. It’s my every day driver to work so was scared to tear too far into it if I don’t have the parts ready to fix it before the week day. Any suggestions. I’ve still yet to bring it to the dealer and let them put on a diagnostic machine. Only used the hand helds.

Sorry man. For one I don’t understand how when I pull all connectors off they all seem to make a change in the engine except for the one on cylinder 5 but it has current going to it. Secondly. If Cylinder 5 is the one getting the misfire to it. Would a lifter cause a misfire? Third. When we did pull the valve cover off on the side of cylinder 1, 3, 5, & 7 and he checked the rocker arm position. Since 5 isn’t an AFM lifter would it be stuck in a position that would cause it to seem locked since is inoperable while idling?

The spark plug didn’t look bad at all. The code that keeps showing on all 3 test are p0305 & p0300. Meaning misfire cylinder 5 and random misfire as you said. We didn’t check the pushrods. He just checked that when turning the engine that they were operating normally and when we stopped it he said he had it to where the cam lobes were sitting flat then pushed on the rockers and none could be pushed in this is what he sent me when mentioning collapsed lifter. Well it can't be stuck because when we rolled the engine over both rockers are rocking meaning the lifters are not stuck. If a rocker would be stuck all the way up then your push rod would be loose and probably fall out of place.

When he hooked up the compression gauge we only took out cylinder 5 plug. I just turned the key without engine starting. Just sorta clicked the ignition. Was that correct? About the 300 code yes I did know it was random. Misfires sure throw the computer out of wack. I’m not sure what to do next. Had no visible play in the rockers when taking off valve cover. Could a collapsed lifter be possible with rockers operating as normal. Of course only pulled the valve cover on side of cylinder 5 where the code read.

“Well it can't be stuck because when we rolled the engine over both rockers are rocking meaning the lifters are not stuck. If a rocker would be stuck all the way up then your push rod would be loose and probably fall out of place.” Thats is what I got back from the person I had checking it.

No just a regular tester light. Don’t have means to a noid light. So I assume a trip to the dealer would be the next trip before a tear down.

I’m not sure which scanner was used. 3 different times with 3 different people. Got same codes each time. Did a reset and of course check engine light came back and the stabilitrak lights also. Hadn’t brought it to dealer but did bring it to shop and was told collapsed lifter. Wasn’t too confident from the symptoms so that’s why I brought it to someone I trusted who doesn’t think it’s a lifter because of the checks he and I did plus don’t have the ticking noises typically associated with a lifter issue.

Check compression: 110 at cyl 5 and held Regular Oil & Filter Change 127,000 miles Second Owner Never had an issue for the 5 years I’ve owned it. Was coming back from TN to Louisiana when about 4 hours into the drive the check engine light came on. Put on code reader. Threw code P0305 & P0300. Changed plug wires, plugs, injector & coil at Cyl 5. Put back on reader and got same codes. Took it to my father in law who has had mechanic shop in the past and we ran through all things I wrote up above and still has us puzzled. I assume only way to check for collapsed lifter would be to buy a $500 lifter kit and open it up. Not sure where else to turn. Reason I say electrical is that When I pull connector on injector I get no apparent sound difference but I’m getting current in the connector.

I done that and had someone with mechanic experience check it out and he said everything was moving as normal. Also while off he had me click the ignition whereas the cam was in the flat position. He checked all the rocker arms for any play and also pushed down on them to see if a lifter was collapsed and none of them had any play or issues. Cylinder 5 which is what the code pointed to has a new coil (getting current), new plug & wire(getting fire) and new injector (which we thought it could be) and still throwing the code for that particular cylinder. We unplugged every connector at each injector and clearly heard a difference in the engine except for 5 which made no diffference in sound. We checked for current at that connector and it’s getting voltage. So we are stumped. I mean if the lifter were to be collapsed at the cylinder wouldn’t there be a sign of it with the rocker arms. Also why would that be the only connector plug when pulled make no difference in engine sound. Could still get something even with a collapsed lifter right? Would pulling the head be the only soulution at checking it? That’s basically a $500 kit for nothing if it isn’t the lifter but I’m not sure what else to do or try or think at this point. Like I said we are stumped. Also the traction control light comes on when sitting in idle. Once it gets rolling it goes off. I put a pic of the valve cover off.

We checked the wire with a test light and everything seems to be getting voltage. Even used a jumper wire and have voltage.

This model truck has the AFM lifters. But anyways we pulled the valve cover and checked the rocker arms and all seems to be functioning fine. All of them are tight and when pushed down on do not go down with the cam flat. Is it still possible the lifter could be collapsed without any telling signs from the rocker arms? Would a collapsed lifter cause no change in sound when pulling the injector connector plug like the others do?

I have a 2012 GMC Sierra with 5.3L V8. I started to get a misfire while idling. I plugged in a code reader and got a p0305 code. Misfire on Cylinder 5. I changed plug wires, plugs, coil pack #5, injector #5. When I pulled the connector for each injector I got a difference except for #5. No change. I have swapped coils & injectors and still get the same reaction from only Cylinder 5. Checked for fire and it’s definitely getting fire. Checked the wire connectors with a light and it’s getting current. Just don’t understand why pulling that wire connector makes no difference and the others do. Also pulled valve cover and rocker arms operating just fine. Everything seems to be in great working order. What could it be? Is it grounding out somewhere before or after the ECM? I’m confused on this one. Any help would be greatly appreciated. TIA