My GM AFM engine makes a knocking sound, could I have a stuck AFM lifter?

​

Yes, there is a good chance you have a stuck lifter. Don't just assume that is the case though. It is worth diagnosing properly first. Be sure to check the basics. If you have a misfire check for misfire history and codes to identify the suspect cylinder. If you don't have that Use a mechanics stethoscope to pinpoint the noises location. If it is in the rocker area the loudest pull the valve cover for the suspected side. Check for loose rockers. If you don't find an turn the engine over and check again. If you do find a loose rocker pa attention to what cylinder its on If it's on 1, 4, 6, or 7 you could have a failed (collapsed) AFM side of a lifter. Pull of the rocker and check the pushrod. Also be sure to check valve spring and valve height just in case. It's not uncommon to find a bent pushrod in LT Based engines newer than 2014. See m solution below for this. If all looks good but the rocker was loose you most likely have a stuck Collapsed AFM portion of a lifter. This is where m specialized Lifter release tool comes in. It is designed to unstick AFM lifters. However, using this technique requires Disabling AFM in the tune and I recommend m VLOM plug with this trick. Especially in LT based engines where the VLOM is the main source of failure. M Lifter release kit can be found HERE.

​

My engine has fuel and spark and doesn't have a knocking sound. Why does it misfire? 

​

You might have a spun lifter from a bad plastic guide. Using the starter relay with the key off, spin the engine over. Make sure not to jump the wrong terminals as it could damage the ECM. It is terminals 87 and 30 if ou look at bottom of the relay. The newer LT based engines with DFM may require jumping 2 relays. Vlom Must be on for this test. While it is spinning watch the suspected rocker move. Make sure that it rocks at least 7 to 12 times before you let up on the starter. If the rocker moves good the entire time, do it a second time within 2 minutes of the first. If the one rocker stops moving before then, it is getting fed oil pressure and is likely spun. However, if two rockers stop moving then you likely have a leaking VLOM. You can determine a spun lifter by looking at the side of the lifter. To see the side of the lifter you need to pull the VLOM and clean out the oil tower of the suspected lifter with cleaner and shop air. Once cleaned you can look down the oil tower and if you see a hole in the lifter it is not spun. If however you see only shiny metal or a flat surface then the lifter has spun due to a bad plastic lifter guide. When this happens you will need to replace the camshaft and all lifters. This would be a good time to do a full AFM/DOD delete where you remove all AFM components and replace them with non AFM components. 

​

 I do now offer Full AFM and DFM delete kits. DFM listing Coming Soon!

 

 

Why do AFM lifters fail in the first place?

Also: Why is my oil pressure low?

​

Minimum oil pressure for AFM

 

Minimum oil pressure spec is too low and should be alarming you at 25psi. The magic number is 26psi per gm. This means if the system ever drops below 27psi at the lifter during activation it will cause damage to the lifter because it doesn't disengage the locks fast enough for the valvetrain events.

 

LS based 2005-2014

The main source of failure for the LS based (2005-2014) systems comes down to low oil pressure. If the pressure ever drops down below 27psi @ the lifter while the system is activating, the locking paws will not disengage the locks fast enough causing damage. This is why it tends to happen on higher mileage engines. As engines age the tolerances will loosen up and the oil pressure will drop. That is why I consider it a bad idea to leave the system active once it has failed. The most common loss of oil pressure is from the following:

 

(Consider a bunch of loose bolts on the VLOM and/or leaking gasket could also cause lifter lock bind/failure.)

 

(Most to least common from what I have seen)​

---1: Plugged screen under pressure sensor (not applicable After VLOM Mod)

---2: Second camshaft bearing (especially in 2009-2014 due to VVT option built into camshaft combined with poor quality bearings)

---3: Plugged oil filter and/or oil sump (Engine flushing with changing filters during can help with these if done right)

---4: Oil sump o-ring failure (can be tested by overfilling oil by 1-2qt then placing vehicle nose down on steep incline. If pressure goes up expect o-ring failure.)

---5: Lifter bleed off (typically comes with oil consumption when on the driver's side. Can be tested by running the vehicle with valve cover off. If any rockers are spraying oil then those lifters have severe bleed off)

---6: Weak or bad secondary pressure relief valve. (located in the oil pan, can get debris lodged, lose spring pressure, or have spring fail.)

---7: Overall worn out engine or bad rod bearing. (The bottom end of these typically won't wear out until well over 400k miles if reasonably maintained.)

​​

LT based AFM 2014-2020ish direct injection

The main source of failure for the LT based (2014-2020ish) systems comes down to oil pressure at a lifter when the system isn't active. This is typically an issue with the VLOM unit. It's not uncommon for them to leak and pressurize the oil towers with a low amount of pressure. This low pressure if it gets to be enough will partially activate the lifters causing them to bind and get locked up. This is common even in brand new VLOM assemblies. So I recommend Turning off AFM in the tune and installing my VLOM plug. I recommend LT1swap for the tune service.

​

What about California vehicle emissions?

​

Buy a 2500 or bigger Chevy. That's the only true legal non AFM option in California. 

 

However, there are tons of vehicles running around California that have been deleted with no issues. The big thing now is the new law passed that claims any tune change done within a certain time of the test voids smog testing??? I have no idea how they could actually enforce this. Especially considering the dealership can come out with tune revisions periodically. I still have customers in California doing the lifter release trick and disabling AFM in the tune and no complaints of not being able to pass smog. Considering that law came out over 3 years ago I would think it's safe to assume that it was a bunk law they can't/don't actually enforce. So in theory the products I sell should work just fine. Worst case scenario, sell the vehicle to someone out of state or better yet move out of that expensive dumpster fire state. Perhaps you like California but I can't stand the way it's run myself. 

​

Does the lifter release apply to a 2019 GM?

 

If it is AFM equipped and actually has a Collapsed/stuck AFM lifter, then yes.

 

That is a direct injection engine though so it has a lot of extra things to consider beyond just the lifter. The Direct injection engines after 2014 are prone to other issues such as:

 

-Bent pushrod from factory interference with hole in head and/or spring on AFM lifter, or internal lifter failure/blowout that caused it to bind/wedge. (This has the same symptom as a collapsed lifter in many cases)

 

-Chewed up cam lobe and lifter roller. This is caused by the soft metal the newer cam is made of and I recommend a full AFM delete at this point. The symptom from this is a light ticking in most cases.

 

-Collapsed AFM lifter. This happens on the direct injection engines usually because the VLOM is leaking pressure into the oil towers when it shouldn't. The VLOM mod I do it pretty much needed on these models. I have a video exclusive just for this VLOM unit https://youtu.be/vwdINEsyYL4

 

-Broken timing chain tensioner. Not that common but worth a mention

 

One last thing to note is on DFM. In 2019-2021 they started to implement a system called DFM. The DFM or Direct Fuel Management controls all 8 cylinders instead of only 4 like AFM does. This system wont allow my products to work with it. It has 8 separate solenoids bolted into the block instead of 4 solenoids in a VLOM assembly. It still functions the same but with twice the AFM lifters. It's still unclear as to the reliability of these but I do know they still bend pushrods occasionally.

​​

My LT based engine keeps bending pushrods, what can I do?

​

The Pushrod upgrade are my base factory length pushrods for the bending issue. However I have recently noticed that gm may have used a slightly too long pushrod from the factory. I do have a shorter version on hand though it's not listed yet as I want to confirm my theory first. If you don't mind doing a simple task I would love to hear your input. Click the contact us link. If you take a rocker loose from cylinder that is TDC compression stroke with a straight pushrod a simple task can tell me if its length is correct. All you have to do is using your fingers and a socket, tighten the loose rocker until you just feel it come in contact with both the pushrod and valve stem. Turning the socket will suddenly stiffen up. Then mark the socket in relation to the rocker so you can count the turns. Use a ratchet and tighten the bolt until it just bottoms out. Again it will suddenly stiffen up. Don't tq it down before noting how much it turned. Let me know how much you had to turn it. Over a complete turn means the OEM pushrod length is too much. Less than a complete turn and the pushrod length is fine. If you find it's over a complete turn, when you order I will get you the shorter ones. I already started to build inventory of those so I have a couple sets on hand. Once I have collected enough data from myself and others like you (if willing) I will decide what to do as far as listing on my website goes. 

​

Why did my Tool get stuck in the Block?

​

Tool damage

You likely bounced the tool while hitting it. Sometimes when this happens the pointed end will plunge into the hole of lifter because the tool rotates. This causes damage to the tool. You need to make sure to hang on to the tool while hitting it all the while pushing down on it. This prevents the bounce. As for what to do now.  If its stuck force it out with a Vice Grip and working it while pulling. Once out, take and clean up the damage to the tool taking care not to change the contour portion they actually contacts the lifter. Once cleaned up you can give it another try if needed. Clean out the oil tower hole with brake cleaner and air and you are now good. Any damage to the oil tower doesn't effect the engines ability to function. Remember, the tool is soft to protect the lifter from damage. So if you need to clean it up it's no big deal. Good luck and I'm confident you will get it. If the pushrod is bouncing it's a good sign indicating the lifter is close to releasing.

​​

Why cant I find the premium lifter release tool?

​

We no longer offer the Premium release tool. This is because I upgraded the steel on the standard product and it seems to perform just as well for releasing lifters. So I am able to sell a similar quality part with less cost. The only way I could offer that one again is if I invest in a special heat treating oven so I can heat treat the new steel. The only downside to the untreated one is how it is easier to bend if you hit it sideways. Just like a nail in a board if you hit it at an angle it can bend. The treated one had a harder center section so that was less likely. Otherwise the transfer of energy on the new one is very similar so it does comparable to release the lifter. Someday perhaps I will invest in a heat treat oven and start offering that tool again. Until then, feel free to order the lifter release kit with the standard tool.

​