4.6 stroker in 00' xj need help with pcm tuning and misfire

[bandofthHawk]

Alrighty man. Ill start with the NGK plugs you recommended. Then clean and reinstall injectors. I dont see any black smoke. Ill keep running the 93 octane to be safe. Kickdown cable is good. What do you use to clean the injectors? Sea foam? To verify AFR can i take it somewhere to have them test it using that special tool? Also another noob question : what is the numbering for the injectors? Which way do i count them ? Should i just clean all of them or just the numer four?

[SilverXJ]

Don't clean the injectors yet. Just swap the #4 one with another one. We are trying to diagnose the problem before improving. I guess you could clean them, back flush them with injector cleaner and compressed air. Apply 12 volt to the injector in shorts bursts, not longer that 2 seconds or so at a time. But keep an eye on #4 injector and keep an eye where you put.

[bandofthHawk]

Right. Pinpoint the problem then identify possible solution. Ill keep you updated. Thx again

[Retlaw01XJ]

Yea i hear it (rattling) while I'm on the skinny pedal at all rpm ranges. Easy or hard acceleration its audible.

Guys, have we determined this is detonation and not something else? Detonation is often referred to as 'pinging' since that is what is sounds like.....'tinging' would also describe the sound. It'll occur when the engine is under load, such as mild or hard acceleration. Do you hear anything similar at idle? Noise at idle would suggest a different problem, not detonation.
Detonation is bad. Try to avoid it whenever possible. Ease up on the gas pedal if necessary.
Premium gas should make a noticeable difference when the sound occurs.

[bandofthHawk]

Its been making that ticking / rattling for almost a year. Windows rolled down i dont hear it. Latest change is this odd clacking sound when i turn off the engine. Like a tapping sound that is audible for a second or two after i shut her off. I hope damage hasn't already been done..

[JPrubo]

Sounding like detonation. That noise after you shut it down could be the last of the fuel igniting from the heat of the motor. I have seen older cars do this, because of the mechanical fuel pump and the carb they will actually run after the ignition is turned off, anywhere from a few seconds to a couple minutes. It's called dieseling and can burn valves and pistons.

[SilverXJ]

Guys, have we determined this is detonation and not something else?

Not yet. Could be other problems as well. Broken flexplate, broken/weak valve spring, lifter losing preload. Its hard to determine what something sounds like over the internet.

Here are a few half decent videos of pinging. Most of youtube seems to think any rattle, knock, back fire or sneeze is pinging.

https://www.youtube.com/watch?v=Jpdbvhe7x3k 4:49
https://www.youtube.com/watch?v=6xTWHJADFe8
https://www.youtube.com/watch?v=GGJZ6kKzLus
https://www.youtube.com/watch?v=VhJSEoTNGgo
https://www.youtube.com/watch?v=XEXctZAHdIA

[bandofthHawk]

i might see if I can record a video and post it here. wow that f150 sounded god awful. yea mines not that bad...

[bandofthHawk]

ok guys got 2 videos uploaded of the engine running. let me know what you think.
http://www.youtube.com/watch?v=0LgTBcZe8M0

http://www.youtube.com/watch?v=quTS1KAUf9g

[gdl]

It's hard to be certain from the video but I'm thinking I hear an exhaust leak. Cracked header pipe or loose bolts maybe?

[bandofthHawk]

Exhaust manifold gasket was replaced last summer. The shop told me it wasnt cracked. All bolts are tight. The previous owner said the bolts like to back themselves out. But at least i know it properly fits the cylinder head.

[bandofthHawk]

You can tell when you take a listen its a consistent ticking sound. Is detonation usually more erratic / spontaneous?

[SilverXJ]

I couldn't tell anything from the videos.

[bandofthHawk]

How do i inspect the flexplate and bolts?

[SilverXJ]

Remove the inspection cover from the bell housing. IIRC two large bolts and nuts and two small bolts