AFM Issues / Misfire

[Peter Tremonti]

I finally got the the oxygen sensor holes plugged today. New front sensors, wrong rears arrived but still plugged the holes nicely (Only 1 sensor came with the vehicle when I bought it...) Now that the front sensors are reading properly, the P0300 fault is showing up along with the P0315 (P0315 was already there when I bought it too.) I tried letting it warm up and do the 4k rpm thing, but it won't set. I'm assuming it's because of the misfire fault that's now showing up with no CEL (because the last guy disabled it somehow (shady used car dealer?)

ANYWAYS... I was looking around with my Autel and looked around in the AFM area. It showed that the cylinder #1 solenoid was activated even though the computer showed the system is deactived. I manually activated the solenoid and at that point it showed that it turned off (it's doing the opposite of what it's being commanded to do). No idea what's going on with this thing. I repeated the process with the other solenoids via the scanner and they're all working fine and there was a noticeable difference in the engine running when they were activated.

Any ideas? I'm assuming a lifter has gone bad but that doesn't explain the solenoid issue. Any ideas?

 

[BG1988]

Any ideas? I'm assuming a lifter has gone bad but that doesn't explain the solenoid issue. Any ideas?

says for P0315 crankshaft position system variation Not learned .. the sensor might be dead/bad. P0300 is a random misfire


these can cause it
MAF sensor
ECT sensor
crank sensor failure
Low fuel PSI
Bad gas
Cam sesnor
bad battery the list goes on


most likely the Crankshaft sensor is bad
bad MAF can cause a random misfire

 

[swathdiver]

Well, I don't think it's cost effective to swap solenoids so if you are going to keep AFM, you'll want to replace the entire VLOM with the updated one or turn them all off permanently in the tune.

 

[OR VietVet]

Yet another reason I love my NBS. In the future you might want to post all this so a guy like me knows what the hell you own:


We recommend that you put all your rig(s) info in your signature so we all don’t have to guess at year, make, model, engine size, trans, rear axle locker…….etc. While you may have posted pertinent info in your first post, you may forget to do it again and the info is needed by us anyway. Makes it way easier on all members that attempt to help, to have that info right up front. It is also recommended that you take a pic of your RPO codes, on the inside cover of the glove box, and post that image in your signature. All this info will greatly help those that will try to help with a problem.


If there is any other info, like upgrades, mods or recent mechanical/maintenance work done, that would be helpful in any post as well. Too many times a question is asked by the poster and after about 10 responses we find out that the poster has done recent work to attempt to fix the problem or work that was done that SEEMS not related to the problem.

Notice the signatures of the other two posters to your problem?

 

[Peter Tremonti]

Yet another reason I love my NBS. In the future you might want to post all this so a guy like me knows what the hell you own:


We recommend that you put all your rig(s) info in your signature so we all don’t have to guess at year, make, model, engine size, trans, rear axle locker…….etc. While you may have posted pertinent info in your first post, you may forget to do it again and the info is needed by us anyway. Makes it way easier on all members that attempt to help, to have that info right up front. It is also recommended that you take a pic of your RPO codes, on the inside cover of the glove box, and post that image in your signature. All this info will greatly help those that will try to help with a problem.


If there is any other info, like upgrades, mods or recent mechanical/maintenance work done, that would be helpful in any post as well. Too many times a question is asked by the poster and after about 10 responses we find out that the poster has done recent work to attempt to fix the problem or work that was done that SEEMS not related to the problem.

Notice the signatures of the other two posters to your problem?

Sorry about that. Just posted this topic right after the introduction page for new members. I added some info but can't figure out how to add a picture in the signature yet. I added my RPO sticker as my profile pic in the meantime.

I wonder if unplugging the MAF would make a difference with the misfire.

I did find out why the CEL isn't on. It looks like somebody disassembled the dash and put some tape over the back of the plastic. Half of the oil pressure idiot light is covered up too. I'll get to that soon.

I changed the oil today just to see what would happen. It looked fine. Not an abnormal amount of metal based on some other vehicles I've driven. It was clear but tan colored like it was changed in the past 1000 miles or so. No difference afterwards in the running or oil pressure areas.

 

[Peter Tremonti]

says for P0315 crankshaft position system variation Not learned .. the sensor might be dead/bad. P0300 is a random misfire


these can cause it
MAF sensor
ECT sensor
crank sensor failure
Low fuel PSI
Bad gas
Cam sesnor
bad battery the list goes on


most likely the Crankshaft sensor is bad
bad MAF can cause a random misfire

The only faults I'm getting right now are for the rear O2 sensors which I know are wrong for it and I have those ordered. Other than the P0300 code that showed up after I replaced the front sensors anyways... We'll see what happens after the rear sensors show up and work on the next fault.

It's not letting me clear the P0315 code for now when I run the test on the Autel. It gets to the point where the test is running and waiting for me to rev it up to fuel cut and let off. I do that and it just keeps saying test in progress.

I'll check the live data and see what the other sensors are doing next week. I have to swap out a transfer case in a dodge tomorrow.

 

[Peter Tremonti]

Well, I don't think it's cost effective to swap solenoids so if you are going to keep AFM, you'll want to replace the entire VLOM with the updated one or turn them all off permanently in the tune.

I'd like to keep the AFM unlike most people it seems. I always liked the idea of it. I'm going to work on the other faults and fix the CEL before moving on with the diagnosis.

 

[OklabyGodhoma]

says for P0315 crankshaft position system variation Not learned .. the sensor might be dead/bad. P0300 is a random misfire


these can cause it
MAF sensor
ECT sensor
crank sensor failure
Low fuel PSI
Bad gas
Cam sesnor
bad battery the list goes on


most likely the Crankshaft sensor is bad
bad MAF can cause a random misfire

After reading very closely I have brought it down to two possibilities. It could be he Ei-ei-o or the QRS-T. Acronyms have different meanings to different people. If you want help from everyone write it all out the first time then use the acronym to represent it. Any yes I speak fluent Bureau-crat-eese.

 

[Doubeleive]

looks to me like you need to do a crank position relearn

 

[Peter Tremonti]

looks to me like you need to do a crank position relearn

I tried that a few times. I don't think it likes that it's misfiring right now. I swapped the ignition parts around from #7 to each other odd cylinder with no difference. Didn't swap injectors yet. Misfire is on cylinder 7 still.

I think I should do a compression check but the random alarm going off and dimming lights is what i'm working on at the moment. Thinking the BCM is dying on me (if that controls the central locking, alarm, door locks, and all the lights). It has random communication loss with a bunch of modules. I just found out where it is today so hopefully tomorrow I get some time to poke around under the dash and take a look at it.

 

[Peter Tremonti]

looks to me like you need to do a crank position relearn

This is what happens currently when I try to relearn the crank position. It says test is running but then it just sits there thinking until I restart the scan tool.

 

[Doubeleive]

does your scanner tell you to set the parking brake and turn off the ac?

 

[Peter Tremonti]

does your scanner tell you to set the parking brake and turn off the ac?

I know the AC was off but I'm sure the parking brake was not applied. I will try again when I get to work this morning and hook up the scanner.

09:50am - So I tried again after driving to work with the parking brake on and it finally cleared out after 3 tries. Seems like an unnecessary thing to have on, but I guess not. Thanks for the help!

 

[Peter Tremonti]

Found my issue with cylinder 7. The front rocker isn't rocking. I started it up just to see what it looked like. There is some pressure pushing up on the pushrod when the engine is running but not enough to move the rocker. After shutting off the engine, it took about 15 seconds before the pushrod fell back down out of the rocker pocket.

Aside from deleting the whole AFM system like most people do. Would you recommend replacing just the bad lifter and see what happens or swap the whole bank of lifters while it is apart? And at that point would it be worth replacing just the AFM lifters or all i on the one bank?

Lots of questions. Going to order parts tomorrow so I'm looking for recommendations before then.

 

[swathdiver]

View attachment 249547Found my issue with cylinder 7. The front rocker isn't rocking. I started it up just to see what it looked like. There is some pressure pushing up on the pushrod when the engine is running but not enough to move the rocker. After shutting off the engine, it took about 15 seconds before the pushrod fell back down out of the rocker pocket.

Aside from deleting the whole AFM system like most people do. Would you recommend replacing just the bad lifter and see what happens or swap the whole bank of lifters while it is apart? And at that point would it be worth replacing just the AFM lifters or all i on the one bank?

Lots of questions. Going to order parts tomorrow so I'm looking for recommendations before then.

You'll have to decide how much money to spend and how long you want it apart. If you just pull the head on that side, replace all the lifters and lifter trays. You can also get the new valve cover to reduce oil consumption and it is SOP to replace the VLOM as that is what usually causes the lifters to fail. The latest parts are far more reliable than the originals.

 

[Peter Tremonti]

Time apart doesn't matter at this point because I bought it to flip it once it runs well enough, and decide if I like the body style enough to get a hybrid. This one was less than half the price of the one I was interested in and I'd rather get familiar with one that's going to be sold before I trade in my 2005 Suburban.

I'm fixing things as I find them to be a problem. So far, there have been some switches bad, weather stripping for the doors, tail lights and harnesses (one of which I think has a bad ground pin again), completely filthy inside, missing quarter glass, and a few other issues to name a few. If I can make a couple dollars on it and get familiar with the new body style, I'm all good.

 

[Peter Tremonti]

Decided to take the head off and throw a set of AFM lifters from ebay into it and see what happens. I'll take out the oil pressure sender and check the screen while I'm there. If everything works out fine after that then I'll be happy. Otherwise, the intake and VLOM are easier to take back off and do afterwards compared to taking off a head. Should have all the parts here by next week.

 

[Peter Tremonti]

Finally got around to swapping in a new set of AFM lifters. The misfire is gone but it's clattering like crazy still. I took off a valve cover and let it run and only saw oil flowing freely out of the front and rear lifters (only 2 of the 8). The oil pressure is around 40psi at a cold start and drops slightly down to around 30 when it warms up. It does stay at or over 40 while driving 30mph depending on load.

I've already taken off the pan and replaced the pickup tube. The pan had the least amount of sludge I've seen in one of these engines so far at maybe 1/4" in the corners only. I seem to be finding differing opinions about which oil pump goes into an AFM motor. Advance auto says it takes a melling M295 or M296. Melling's website said a 10355 would be needed for an AFM engine and the original oil pump is already a high volume pump based on the additional flow required by the AFM parts.

I have not bypassed or plugged the relief valve in the oil pan even though I had it off to do the o-ring on the pickup tube. I am wondering if it would be worth it to port and shim the oil pump and see what happens before swapping in a new one. I haven't seen any videos of before and after porting or shimming a pump on an LS. I've only seen videos of how it SHOULD help after doing so but no direct comparisons of before and after.

It is going into V4 mode with no issues at the moment and it doesn't seem to drop oil pressure like I've read it could when that happens. There are no more misfires at this time just ticking and lower than I'd like oil flow from the lifters.

Thoughts?

 

[George Owens]

I’m just starting to get the tick as well, did you replace all the lifters or just the AFM ones?

Finally got around to swapping in a new set of AFM lifters. The misfire is gone but it's clattering like crazy still. I took off a valve cover and let it run and only saw oil flowing freely out of the front and rear lifters (only 2 of the 8). The oil pressure is around 40psi at a cold start and drops slightly down to around 30 when it warms up. It does stay at or over 40 while driving 30mph depending on load.

I've already taken off the pan and replaced the pickup tube. The pan had the least amount of sludge I've seen in one of these engines so far at maybe 1/4" in the corners only. I seem to be finding differing opinions about which oil pump goes into an AFM motor. Advance auto says it takes a melling M295 or M296. Melling's website said a 10355 would be needed for an AFM engine and the original oil pump is already a high volume pump based on the additional flow required by the AFM parts.

I have not bypassed or plugged the relief valve in the oil pan even though I had it off to do the o-ring on the pickup tube. I am wondering if it would be worth it to port and shim the oil pump and see what happens before swapping in a new one. I haven't seen any videos of before and after porting or shimming a pump on an LS. I've only seen videos of how it SHOULD help after doing so but no direct comparisons of before and after.

It is going into V4 mode with no issues at the moment and it doesn't seem to drop oil pressure like I've read it could when that happens. There are no more misfires at this time just ticking and lower than I'd like oil flow from the lifters.

Thoughts?

View attachment 262252 View attachment 262253 View attachment 262254 View attachment 262255

 

[Peter Tremonti]

I’m just starting to get the tick as well, did you replace all the lifters or just the AFM ones?

I only did the AFM lifters on the odd bank. It fixed the misfire but not the ticking.

I have since bought an OE higher flow oil pump and cleaned up the casting while I was waiting for an opportunity to install it. Hopefully I'll get it installed before the end of the year.

Something I've found out according to Melling and Advance Auto Parts is that my engine takes an M295 pump. Everything I've read elsewhere says that the AFM and VVT gen 4 engines use a higher volume pump so that's what I bought.