I have a 2004 DII with a swapped AB engine with about 40k on it and 198k on everything else. Occasionally, I get a loud, scary knocking noise coming from deep inside the engine at idle. I have tried everything to diagnose, but really think it is linked to some sort of ignition timing issue. It goes away when I rev the engine. It doesn’t seem to be tied to being hot or cold. When I replaced the battery, it went away completely. Some days it is there. Other days it is as if it a brand new truck. This has me thinking it is a sensor or computer issue that is not worth troubleshoot, but rather just replacing the sensors or computers in that loop to be certain.

What sensor systems are involved in actually adjusting the timing on these engines? When it goes awry, I get the loud knocking, engine misfire codes on cylinders 1, 2, and 5 as well as the old “random misfires detected” code. I replaced the coils about 10k ago, new plug wires, new plugs.

is this a symptom of that crankshaft sensor I have read about?

thanks!

Ryan

 

I can’t see how a crankshaft sensor could cause this.

 

Hmm. This is a new one. Does not seem like any failure mode of crank sensor I've ever seen on these...

All the usual suspects seem a little incorrect based on your description ie
Rod knock
Slipped liner
Etc etc

Can you post a video w/ good audio?

 

Good to know. Thanks.

I’ll see if I can get it to happen again. It has to be electrical because it isn’t anything that happens regularly. So, unless the previous owner wasn’t being honest, it should have the fixed liner features from AB. Not sure how to confirm.

I’ll see what I can do to get a good video.

not that I want to hear that noise again… but it’s for research purposes.

thanks.

 

What type / viscosity of oil are you running in this btw?

 

UPDATE:

I am pretty certain this is an electrical issue. Here is my diagnosis again:

1. The knocking only happens when the engine is cold and idling. It happens in the morning and I am fairly sure it is just misfiring. When the engine is warmed up after the 2 mile drive to drop my kids at camp, it does not do it for the rest of the time the engine is driving, idling, etc. It runs beautifully when warm, even at idle.
2. The knocking goes away when I rev the engine.
3. I have new coils, new wires, new plugs, oil change with 15W-40, new O2 sensors, new exhaust, and 40k on an Atlantic British long block in there.
4. I have the following codes triggering a blinking CEL:
   1. P0300: Random/multiple misfires detected
   2. P0301: Cylinder 1 misfire detected
   3. P0305: Cylinder 5 misfire detected
   4. P0302: Cylinder 2 misfire detected
   5. P1300: Misfire detected sufficient to cause catalyst damage
   6. P1171: Oxygen sensor system too lean fault banks A&B
   7. P1174: ???
   8. P1319 Misfire at low fuel level (full tank)

Is there a system that is kicking in when cold that seems to have an air leak or some other stupid sensor-related input to control the timing? I am really struggling with this one.

Thanks!

Ryan

 

Have you experienced this with the hood up? SAI truck? Does it happen every morning, or only sometimes? Always the same codes? Although there are smalll changes in timing when cold it is not enough to cause the symptoms you are seeing. I would recommend a methodical troubleshooting method, change one variable at a time. start by swapping plug wires 5 and 6. Look for a change. Swap coils left and right, look for a change.

 

Hood up, yes. Every morning, yes. Just now after sitting for the day, yes. Cold engine = banging until it is hot and then no problem at all.

Great idea about switching plug wires, but wouldn’t that recreate the same problem? I get the concept, but don’t know the timing sequence well enough to know if there is any magic combination that should work, but would allow me to rule out the specific cylinders or wire.

It does seem like the SAI could be a culprit. How the heck do you check that?

Thanks so much!

Ryan

 

I would try a new set of spark plugs. And examine the old plugs for clues, like color, gap, oil. I had an ordeal with counterfeit plugs from ebay a while ago. At 40 k miles, it is probably time for new plugs, depending on type of plug of course.

 

Two possibiities, one is what you are hearing is an SAI leak and not a banging at all. Try disconnecting the SAI solenoid (you can trace the SAI vacuum lines out till one ends in a solenoid) or just disconnect the vacuum line (engine will idle a little lean and throw a code but otherwise run fine) from the manifold or vacuum accumulator. Swapping the plug wires will rule out the plug wire in question and you could swap coils left and right, but I would try the SAI test first.