How To Stop Pre-Detination Rattle?

[LFD2037]

I cannot believe this has gone on for 10 pages! You can lead a horse to water but if he TELLS you its not water than walk away. They have given you the correct ways of ruling things out and continue to help, yet you do not actually try to do these things because of various reasons. Why ask the same questions if you do not like the answers. If you tried half as hard to fix the thing as you do telling people "thats not it" it would be fixed already. Sorry but you have some awesome guys giving you great advice, it may take a bit more actual physical work on your part to get it diagnosed.

I REALLY don't think everyone is grasping this fact:
It ONLY does it when engine is heat soaked and AMBIENT temperature is above ~85*.
1) If it was a lean issue would AMBIENT temp be THE factor that makes/doesn't make it happen?
2) If it was a valve issue, would AMBIENT temp be THE factor that makes/doesn't make it happen?
These are the 2 questions I've been asking but, unless I missed it, haven't been answered anywhere in this thread. I've been told 20 different things to check, replace or change. I've thrown a significant amount of money at this already as you will see if you read thru the whole theead( which is quite long). This situation ONLY happens in June, July, August and September. The other 8 months out of the year it does NOT make this rattle/clatter/pinging/detonation/pre-ignition/marbles in a tin can sound. I truly appreciate everybody's help. I really do. I'm not disregarding anyone's opinion, seriously. If I could get an experienced answer to the 2 simple questions above then I'll know which direction to go without just throwing more good money at bad. If I can't get the answer to the 2 questions then I'll just move on. Thanks again, everybody, for your help.

 

[scottryana]

Yes, ever hear of intercooling . It cools the air to ....... Prevent knock

 

[Alleycats]

Seems like a no-brainer that heat soak could send it over the edge (detonation), but still the underlying issue is temp unrelated.

 

[scottryana]

And I don't want you to feel like you are getting ganged up on! I just seemed like you were completely mystified by this problem but were blowing off a lot of suggestions as to how you might be able to fix it. I just wanted to give my ideas and you can do with them what you want. You might just want to run it as is, since it doesn't seem to bother you too terribly. But I think it is a problem and not just a nuisance and in the long run continuing to run it is probably going to end poorly. just my opinion.

 

[Reelitchy]

Would like to see you get this fixed,seems like a problem that occurs regularly with these engines.
as far as your ambient air question, I believe it has to do with air temp- warm air is less dense and cold air is more dense. You get more air in a given space when it is cooler. You are getting more air in during the colder months of the year.
Saying this I don't have a diagram for your truck but I believe it has a air temp sensor that could also be bad, maybe not. Does your scan gauge monitor it?
Also I believe you only took one plus out last year, did you look at them all? Maybe it's just one or two injectors. Lots of variables and lots of good info on this thread.

 

[Wayne]

I know I'm getting in on the tail end of this thread, but I've experienced pre-ignition on my '96 and it was caused by two things, too much advanced timing, and low octane fuel. It is much worse on hot days or when the engine is under load, i.e. going up a hill. Good quality 93 octane fuel, 3 degrees BTDC timing and life is good.

 

[LFD2037]

About to be 3 years since I started this thread & it's still the same! I haven't attempted any fixes on it in the last 2 years. I'm going to try to take it to the local LC shop & see what they term the noise as & possible fixes. I'll post back w/their findings. It's been a long trip so thanks for tagging along!

 

[Sambosuda]

Lol let us know. Mine is driving me crazy.

I recently went back to regular 87 gas and it's definitely happening more often than with 93.

 

[Haspin FJ]

Take this for what it's worth. Sorry if the back story it's too long.

I bought a 97 a couple years ago and drove it back to Ohio from Gorgia where I purchased it. When ingot back it was the coldest day we had had in years (like 17 below) and I drove it to the BMV for my out of state inspection. On my way he we have a big hill out of a river valley that while climbing I clearly remember thinking to myself how this was the best rig I ever bought it was running so good, probably helped bt the oxygen levels in the super cold air. Anyway, I got home only a mile or two later and as I turned in the dive way felt a hesitation. Looked in the mirror and saw the billowing white smoke.. yes blown head gasket. I felt lucky since I would always be worried about its condition and it made it all the way home and back to my driveway before it failed.

To the point. Me and a good mechanic friend fixed the HG and upon completion had a strange rattle and detonation occurring. It reminded me of when I installed a timing belt a tooth off on an old 91 v6 toy pickup I had previously. It was noticeable and concerning enough that my mechanic I could tell definitely had concerns we had an issue. After driving for a couple days I figured out the engine hoist hook on the rear passenger side of the engine must of got put back on wrong and was hitting the hard AC line on the fire wall when the engine torqued. Bending the bracket to emininate the interfere totally eliminated the noise and power issue. It almost seemed like the rattle was causing an issue with the knock sensor and timing. I cant explain this and expect some skepticism, however it's been perfect for over 15,000 miles and multiple trips on and off road since this was resolved and again runs so good that I feel again it was a great purchase. Make sure nothing is hitting or rattling that could cause a false reading by the knock sensor.

 

[IronCladLou]

Just thought I'd add an update to this thread as I had this same issue. It suddenly occurred to me the other day that my "detonation right at throttle tip-in" had gone away. Completely silent in the situations where I used to hear it all the time (pulling away from stop signs, etc.).

Here's what I did....nothing. It just went away. Back when this started a year or two ago (right after I replaced my distributor o-ring so I suspected I screwed something up) I started running higher octane gas, but even 93 didn't fully eliminate the rattle. Obviously I had checked timing, etc. and it was right on 3 degrees. A gas station on my way home from work sells 91 octane 100% gas, so I started running that. No change in the pinging, but I figured it was better than running 87 and it's not much more that 93 octane, 10% ethanol. I figured I'd just live with it.

Fast forward to this summer and...no pinging. I realize this post has no value at all, but thought I'd update since things never get better for no reason.

 

[landtank]

@ppc
Timing was set correctly using the paperclip in diagnostics port at 6-7* (Ultragauge says 6.5* at idle most of the time).

I haven't read the whole thread so my apologies if this has been said.

I'm sure that the UG or similar device should show @3* at idle with the timing set at factory specs.

What is the distributor's hold down bolt's position in relation to the slotted hole in the casting when timed to factory specs?

You might be a tooth off.

 

[LFD2037]

I haven't read the whole thread so my apologies if this has been said.

I'm sure that the UG or similar device should show @3* at idle with the timing set at factory specs.

What is the distributor's hold down bolt's position in relation to the slotted hole in the casting when timed to factory specs?

You might be a tooth off.

That was replying to it being set properly at 6-7*. It's now set at 3*. Still does it. I haven't spent the time to go by a mechanic as I've lost interest in this problem. Maybe I'll re-address it one day and update this thread.

 

[landtank]

If the dizzy is set to 3* I beleive you should see the timing during idle mimic that.

I'll double check when I get home.

 

[baldilocks]

That was replying to it being set properly at 6-7*. It's now set at 3*. Still does it. I haven't spent the time to go by a mechanic as I've lost interest in this problem. Maybe I'll re-address it one day and update this thread.

I hate pinging and detonation so I understand your concern and I don't think I would just let it go. I have had three 80's over nearly 4 years and have never experienced pre-ignition. My last rig was an old Dodge and one year it suddenly began knocking and pinging. I ran Lucas fuel system cleaner for several tanks and switched to Chevron gas. I blame the problem on carbon deposits built up on the pistons and possibly caused by lower quality gas.

My question is: what are those expensive "knock" sensors for anyway?

 

[elripster]

Are you absolutely sure your EGR is working properly? It's job is to cool the burn to reduce NOx production. Spark and fuel curves assume that is present. The knock sensor should retard the timing if it detects knock but if the EGR is not working at all it might not be able to retard it enough.

My heat shield rattles and used to sound like a ping. Now it is just sounds like rattling sheet metal.

Frank

 

[LFD2037]

If the dizzy is set to 3* I beleive you should see the timing during idle mimic that.

I'll double check when I get home.

Timing light shows 3* and Ultragauge, at idle with AC off in park, shows 3*.

 

[LFD2037]

Are you absolutely sure your EGR is working properly? It's job is to cool the burn to reduce NOx production. Spark and fuel curves assume that is present. The knock sensor should retard the timing if it detects knock but if the EGR is not working at all it might not be able to retard it enough.

My heat shield rattles and used to sound like a ping. Now it is just sounds like rattling sheet metal.

Frank

I have no CEL and have tested the components. They tested with proper working results.

 

[LFD2037]

I hate pinging and detonation so I understand your concern and I don't think I would just let it go. I have had three 80's over nearly 4 years and have never experienced pre-ignition. My last rig was an old Dodge and one year it suddenly began knocking and pinging. I ran Lucas fuel system cleaner for several tanks and switched to Chevron gas. I blame the problem on carbon deposits built up on the pistons and possibly caused by lower quality gas.

My question is: what are those expensive "knock" sensors for anyway?

It's been doing this going on 3 years! If I use 92-93 octane it's almost non existent near the end of that full tank. That's the confusing part and I feel like I chased my tail trying to figure it out.

 

[elripster]

Well if you are sure the EGR is opening and flowing exhaust that nixes that.

Knock sensors detect spark knock long before you can hear it and retards the timing to compensate. If you can hear spark knock, it is very bad and can damage the engine. The sensor could also enrich the mixture as well.

Ok so lets assume all of that is working. Here are some out-loud thoughts.

A bad injector that is not squirting enough could cause this issue in just one cylinder such that the other sensors compensate accordingly but not enough for that one cylinder. Could there be an air leak at the intake/head interface such that one cylinder is running lean? I think you are using typical plugs so that is likely not it but once a long time ago I had issues using those Bosch +4's though on a different make of vehicle where it caused excessive spark knocking. Otherwise, I am thinking you might have excessive carbon buildup.

So what new thing can you do? Well, to get rid of carbon you can flush the cylinders. This made a world of difference on my 3FE. You pull the plugs, pour Marvel mystery oil into the cylinders, turn the engine over by hand a few times, let it sit over night, put a towel over the plug holes, crank the engine to clear the oil, reinstall the plugs, and go test it.

Cats, are the original? I have had issues like this with severely plugged cats. They are expensive but if they are plugged they can cause a variety of issues depending on the vehicle intake style (carb'd vs. injected, OBD1 vs. 2...) It's rather hard to

Frank

 

[LandLocked93]

Bump for posterity

IME a tooth off on the dizzy is a nogo sitch. No amount of adjustment could make an OBD1 1FZ run right on the wrong tooth. Tho I've seen 2 two different dizzys on the correct tooth yield a different landing in the bolt slot @ the same degree setting.

@LFD2037 isn't the only one to go to the lengths he has to resolve. And yet the efforts fall short.

I courageously submit, in the interest of expediency for those who read a book beginning with the last page, that the cause of what I would call "pinging" MUST be one of three things:
1) carbon build up on the piston tops - on the basis that no one has the pinging issue with new pistons
2) head gasket thickness & spark plug heat range* - for those who had the prob after a HG job - on the basis that some suggest wrist pin clearance is also a factor. This could also suggest that just a change in oil viscosity can lead to pinging.
3) fuel quality - on the basis that the OPs issue only happens certain months of the year.
*Full disclosure - I'm running 90919-01191 and still have pinging.

Fuel flow is ruled out by those who replaced all that and still have the issue. Filters, socks, injectors, resistors, relays, etc.

One thing I've not seen mentioned...what does the multi-sprocketed cam do? I've had a "wranc wranc" noise coming from the top of the head since I've owned it (2017/276kmi). RPM-dependant, it quieted at idle but got louder to 1krpm then went away above that.
Over time, its vocal rpm has lowered to idle speed, sounding less adamant but still there. Over the same time, the pinging slowly appeared. Do those sprockets affect timing, combustion, exhaust? And would clearance in that area cause pinging?