How To Stop Pre-Detination Rattle?

[LFD2037]

'97 w/165K miles. Timing was @ factory 3* & I changed it to 6.5* but had pre-detonation w/factory timing. New plugs, wires, cap, rotor, yada yada yada. Besides using 93 octane fuel (which I did & it got rid of 90% of it) what can I do to get rid of pre-detonation rattling? Thanks.

 

[Mixelplix]

If you're getting ping at 6.5* something is really strange. Have you looked in your cylinders to see the tops of the pistons? Use a LED light and the spark plug hole. Are they literally caked with carbon or crud?

I suspect you're hearing something else. I have a 3fe so I'm a little different, but are your valves adjusted? Do you have an exhaust leak? (exhaust leaks are often misdiagnosed as ping)

 

[LFD2037]

I got it @ factory 3*! I have not looked down in a cylinder. It is w/out a doubt pre-detonation (pre-ignition I think some call it).

Here's a video of the sound:

 

[Overland Tailor]

Sometimes hard to distinguish, BUT if you used 93 and it "almost" went away I'd be confident that its detonation and not some random rattle.

Confirm you have timing set correctly as per the FSM or MUD procedure - Also confirm you had pre-detonation at 3*, but advanced it to 6.5*???

Parts changed were OEM or aftermarket?
Fuel Filter Changed when?

Piston tops will have carbon and some crud... Boogers on there can cause pre-detonation, but usually only when running advanced timing so I'd focus elsewhere initially..

I'd Set your timng back to factory and get it resolved there. Advancing another 3.5* is going the wrong direction and hope it was a mistype in your post.

Any codes set?

Thanks,.

J

 

[LFD2037]

Sometimes hard to distinguish, BUT if you used 93 and it "almost" went away I'd be confident that its detonation and not some random rattle.

Confirm you have timing set correctly as per the FSM or MUD procedure - Also confirm you had pre-detonation at 3*, but advanced it to 6.5*???

Parts changed were OEM or aftermarket?
Fuel Filter Changed when?

Piston tops will have carbon and some crud... Boogers on there can cause pre-detonation, but usually only when running advanced timing so I'd focus elsewhere initially..

I'd Set your timng back to factory and get it resolved there. Advancing another 3.5* is going the wrong direction and hope it was a mistype in your post.

Any codes set?

Thanks,.

J

Timing is set correctly @ 6.5-7* advanced. I figured if it did it @ 3* may as well do it @ 6.5-7*! I know lowering, or retarding, the timing is how you make it lessen or go away but if it does it @ the factory setting then the timing is NOT the problem.
ALL parts are OEM.
I don't know if fuel filter has ever been changed. What difference would it make?
Why change timing back if it did it there as well? The timing isn't the issue.
No CEL but UltraGauge does keep saying there's a 'pending' code of 0130 (front O2) but it doesn't actually throw a code, only 'pending'.

 

[scottryana]

Fuel filter could be clogged causing a lean condition causing the detonation. I would check AFR's and see where you're at.

 

[Overland Tailor]

Why change timing back if it did it there as well? The timing isn't the issue.

We will agree to disagree - The timing might not be the entire causative factor, but could contribute to it.

Also because their are different levels / amounts of detonation at different load points when you are driving and you can't determine how much you are getting.One thing I will promise you is that you are getting more detonation running more advance. I you have detonation at 3 or you will have more at 6 degrees as you shorten the knock threshold.

You also start diagnosing and making changes from stock configurations. Trying to find your cause running an extra 3.5* of advance is throwing money, time and effort away.

Just trying to help.

 

[Overland Tailor]

Also on the O2 sensors you are getting somewhere now! Air / fuel and timing - That's your focus point.

I would look to test or replace if they are originals.. I like to change 02's around 90-100K on all vehicles working or not as it keeps other problems from sneaking up..

Good luck -

J

 

[LFD2037]

Fuel filter could be clogged causing a lean condition causing the detonation. I would check AFR's and see where you're at.

Do you know if I can check AFR w/my Ultragauge? 14.1:1 is what my HD is set to @ factory. Is it the same for these rigs?

 

[bsmart82]

You need to put the timing back to stock until you eliminate the detonation. More timing will only make it worse and is not doing you any good. I'd look at the O2s since there is a code and maybe try some top engine cleaner.

 

[Alleycats]

Engine temp. when pinging?

 

[scottryana]

No you can't pull AFR's off the scan gauge, the stock O2's are narrow band and basically just keep the engine in a very narrow operating area but don't give an exact reading. Would need to get a wideband in the system somewhere, preferably before the cat, but you can clip one on the tailpipe and get fairly close.

 

[etarasoff]

I'd agree with the advice above to retard the timing back if you're experiencing pre-detonation. You don't want to cause any sort of damage while this is going on.

I've looked into this a lot before. Pre-detonation, in the absence of some definitive other cause, is commonly (if not usually) caused by a caking of carbon on top of the pistons. There are various hacks people use to try and take care of it. Some people SeaFoam their engine to try to deal with this and other ailments, but the verdict is out as to whether it is effective or not. Old timers will also spritz water (in super limited amounts) in the intake to clean this off (guaranteed results...but dangerous if you use too much! There are videos of people on YouTube showing how this is done).

 

[LFD2037]

bsmart, it's not throwing any codes. It's 'pending' codes on the UG, which isn't really a code @ all.
alleycats, temp is usually between 194-212. Fully warmed up & heat-soaked.
scotty, no way for me to get wideband on it.
etarasoff, I think it's probably carbon. I recently changed the PCV valve & looking inside what little bit of the valve cover I could, I could see a fair amount of soot. I've never used Seafoam but have read it works for some & really messes up others. Since I'm fairly sure it's carbon fouling on top of the pistons I guess I need to figure out the best, safest way to clean them.

 

[tirewater]

When did the pinging start? After doing the cap & rotor?

Does it occur at idle? Pinging at idle with no load is pretty rare, so I'd guess a timing issue over a carbon build up one.

Set the timing back to stock by using a timing light, jumping the connector at the firewall then adjusting your distributor. Stock is 3 degrees.

Your ultragauge will show the timing advance. Whether it's retarded or increased. Look at this value when the pinging occurs. Your knock sensor will retard the timing if it detects pre-detonation. The knock sensor detects this before it's audible to the human ear, so timing should be full retarded by the time you start hearing pinging.

 

[LFD2037]

@tirewater
I've watched the UG when it starts to ping. If I remember correctly it was about 25* when it started but didn't drop from the pinging, only dropped when I left off throttle. I'll watch again tomorrow & make sure. It pings every day when I'm taking off from a start w/a light throttle below about 2K RPM or when I'm WOT above about 3,800 RPM (which I only did to see if it did it on the high side too).

 

[Overland Tailor]

Below 2k taking off is what I would expect as that is high load on the motor.

Set timing back to stock and I would suggest a methodical approach starting with things that are already telling you something is wrong.

A pending code is just that. It's telling you something is not correct and just about outside the parameters. Something like an o2 sensor can go bad over time. These trucks tell you long before they will leave you stuck.

Take the o2 out and test it. I bet you it won't meet spec. If it does not, replace them all.

Next make sure your intake tract from MAF to intake is good and sealed and I would also take this time to clean the MAF. Let's make sure you don't have unmetered air leaning you out or a dirty sensor.

Next take a good look at your fuel system. Not likely the pump, but you said you have not replaced the filter. Do you have documentation it was done by PO's? If not assume original and replace it.

Good luck on this and keep us posted. Hope some of this helps..

J


...half a turn before it breaks

 

[ppc]

Two things not mentioned above are to make sure the spark plugs are in good shape with electrodes that are not worn (you said they were new), properly gaped and the correct heat range. Going to a colder plug would help but should not be necessary on a properly running normally aspirated engine. Setting to the timing to 6.5 degrees of advance should not be a problem. Make sure you're not running cheap gas with proper octane. It should not require premium. You say the timing has been set properly but was it set when in service mode or base mode (paperclip shorting terminals in the diagnostic connector)? The knock sensor should detect the knock and very quickly reduce the timing advance but it can't lower below what is set for base timing. Is it very possible the knock sensors or associated wiring could be bad but I would think that would generate a check engine light. Do you have a code reader to check for codes? Is the pinging constant during light or medium acceleration or only briefly?

 

[LFD2037]

@ppc
Timing was set correctly using the paperclip in diagnostics port at 6-7* (Ultragauge says 6.5* at idle most of the time). Plugs are Toyota plugs spec'd for my rig. I've checked for codes and there are none. It is constant if throttle held at a specific RPM range. It's from about 1,600-2K slowly accelerating or about 3,800+ when floored. I've tried gas from every station in my neck of the woods. I've added 2 bottled of Techron to 15 gal. of fuel. This started right as, I would think, they switched to summer blend fuel. 2 days ago I put a half tank of 92 octane and its the only thing, so far, to improve it but I can still make it ping. Thanks.

 

[tirewater]

@ppc
Timing was set correctly using the paperclip in diagnostics port at 6-7* (Ultragauge says 6.5* at idle most of the time). Plugs are Toyota plugs spec'd for my rig. I've checked for codes and there are none. It is constant if throttle held at a specific RPM range. It's from about 1,600-2K slowly accelerating or about 3,800+ when floored. I've tried gas from every station in my neck of the woods. I've added 2 bottled of Techron to 15 gal. of fuel. This started right as, I would think, they switched to summer blend fuel. 2 days ago I put a half tank of 92 octane and its the only thing, so far, to improve it but I can still make it ping. Thanks.

Oh good, this is better information.

May as well set timing back to 3 degrees while you fix this problem. If you fix the pinging at 3 degrees, it may not be fixed at 6.

It sounds like a fueling or dirty intake/combustion issue. Do you have the supercharger?

What this comes down to is testing & cleaning. Test your fuel pump, injectors, o2 sensor, etc... Clean your throttle body, intake manifold, combustion cylinders.

I suppose the simplest test to start out with is to unplug your front O2 sensor & let the truck run in open loop mode. I don't know the fzj80's FI that well, but in general the ECU will revert to a predetermined FI map for fueling. It will prevent the FI from using the O2 sensor to lean the fueling. Although bad O2 sensors generally cause a rich running system (IME).