Try the timing. Its easy. There are many variables in timing-even slightly mis-machined keyways for the crank and balancer/ mis stamped timing marks/ machining of cam/ gear at cam attachment/Timing chain stretch/advance curve/etc/etc.
How To Stop Pre-Detination Rattle?
- Thread starter LFD2037
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1973Guppie
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agree with this, you should be diagnosing at the fsm set levels on everything, otherwise you are imparting other variables into the equation.
Absolutely agree. What's the term so widely used around here, "baseline"? It applies to troubleshooting too.
LFD2037
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- #186
1) Yes
2) I have no way, or even know of a way, to do that
3) heads never been off so no
4) have not done that
2) and 4):
If the AFR is off, or if there was damage to piston, changing octane would not have an effect, correct?
Just so it's clear, timing is set to factory 3*. It has been at 3* since last summer. When it was at 6-7* the rattle was no better and no worse.
Thanks.
No that is not correct. Octane rating is directly related to antiknock properties. If you're on the edge because of lean condition, build up on the piston/combustion chamber (raising compression) or a sharp edge because of piston damage higher octane will help prevent it.
You say you have done everything but these are certainly things I would want to check right away if I had the same issue.
You say you have done everything but these are certainly things I would want to check right away if I had the same issue.
No that is not correct. Octane rating is directly related to antiknock properties. If you're on the edge because of lean condition, build up on the piston/combustion chamber (raising compression) or a sharp edge because of piston damage higher octane will help prevent it.
You say you have done everything but these are certainly things I would want to check right away if I had the issues.
Get an AFR gauge and have a bung welded in before the Cat or get one that clips into the end of the tailpipe just know that it will probably read a little leaner than true because of the cat.
You say you have done everything but these are certainly things I would want to check right away if I had the issues.
Get an AFR gauge and have a bung welded in before the Cat or get one that clips into the end of the tailpipe just know that it will probably read a little leaner than true because of the cat.
Correct.
Running lean would make it pass state inspection with flying colors. The narrow band O2 should catch a lean condition but they are very marginal. I have seen many people have problems with their O2 sensor and no CEL's.
Creates a venturi effect...so air can be sucked in.
What scottrani says, monitor the o2 on your scangauge. Good luck
LFD2037
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- #193
Like reelitchy said, I've monitored it on my Scangauge and the voltage values are always where they should be. But, I think you said somewhere that it needs to be checked in wideband??? I could be wrong about that, though. I understand wideband is more detailed but if wideband detail is what the ECM needed then wouldn't it have wideband O2's (I don't think they were even available in 1997, though). I just can't wrap my head around, and neither can the 2 mechanic-ish friends I talked to about this today, that it can be running lean with no CEL and the O2 values reading properly on the Scangauge.
I just spoke with a guy that owns a head shop in the town I work. He says its not valves so that's 100% out.
"I just spoke with a guy that owns a head shop in the town I work. He says its not valves so that's 100% out."
I'm sorry, aside from the initial reaction I had about the guy who owns a head shop (Gas Pipe?) I don't understand why you can throw out something because a guy told you so when you haven't verified the correct valve clearance. After all you've been through in chasing this issue down, it seems to me that it might be something you would want to either rule out through hard evidence (correct valve clearance at operating temperature) or possibly find a cause for the problem. Heck, a valve clearance check and adjustment if necessary is part of a 60k service. Tight valves (insufficient clearance) will cause detonation, and if severe enough, burned valves, especially on the exhaust side, because they're not in contact with the seats long enough to properly cool, and a localized hot spot in a combustion chamber will cause detonation.
I realize your contact owns a head shop, but I'm trying to offer suggestions based on close to 30 years of being a professional service tech with certifications from two manufacturers and at least one independent professional organization to the tune of Acura Master Tech & NSX Tech, Lexus Master Tech, and ASE Master Tech (L1). Granted I've been out of the field for a while and didn't do much in the way of run problems while I had my shop since it was mostly gear work and fabrication, but some things about the internal combustion process and the machinery involved are universal.
Obviously it's your truck and your problem, and yours to troubleshoot as you please, but with absolutely no hard feelings and with all due respect, I must bow out. I sincerely wish you the best of luck in finding your problem.
I'm sorry, aside from the initial reaction I had about the guy who owns a head shop (Gas Pipe?) I don't understand why you can throw out something because a guy told you so when you haven't verified the correct valve clearance. After all you've been through in chasing this issue down, it seems to me that it might be something you would want to either rule out through hard evidence (correct valve clearance at operating temperature) or possibly find a cause for the problem. Heck, a valve clearance check and adjustment if necessary is part of a 60k service. Tight valves (insufficient clearance) will cause detonation, and if severe enough, burned valves, especially on the exhaust side, because they're not in contact with the seats long enough to properly cool, and a localized hot spot in a combustion chamber will cause detonation.
I realize your contact owns a head shop, but I'm trying to offer suggestions based on close to 30 years of being a professional service tech with certifications from two manufacturers and at least one independent professional organization to the tune of Acura Master Tech & NSX Tech, Lexus Master Tech, and ASE Master Tech (L1). Granted I've been out of the field for a while and didn't do much in the way of run problems while I had my shop since it was mostly gear work and fabrication, but some things about the internal combustion process and the machinery involved are universal.
Obviously it's your truck and your problem, and yours to troubleshoot as you please, but with absolutely no hard feelings and with all due respect, I must bow out. I sincerely wish you the best of luck in finding your problem.
Even if it did add air ahead of the O2s it would give a false lean reading (too much oxygen/not enough burned fuel) -then richen the fuel mix-creating an artificially RICH fuel/air in the chamber. That would cool the chamber temps and resist pinging.
^ Maybe guy meant that the noise is NOT valves rattling- IS pinging/detonation
Well with no other indications if that sensor is reading correctly you have no way of knowing if it is. You have a possible knock. You are convinced that it is not timing and you are convinced that it is not valves. So the only next step is fueling.
You have a narrow band that is not great even when it is brand new. It does not give you any concrete data just that it thinks that the stream of all 6 exhaust runners are within it's parameters.
Could you have 1 cylinder with a bad injector so that it is running lean and the other 5 cylinders are running slightly rich and still have the combination of all 6 be within the range of the narrow band? Yes you could. Could you have a bad narrow band that is giving you false readings and everything is lean? Yes you could.
These are the kinds of things you need to start ruling out. You can get a wideband and check it, you could pull all the plugs and check them, you could pull and test the injectors, you could get the borescope like I mentioned and check the pistons.
Lots of things to do, I feel like you haven't tried everything yet, and you are kind of giving up on it without really looking into it. Rusco is absolutely right you can not rule out a Head Shops word that it isn't a valve. You have no idea how many times I have had people tell me it couldn't be something only to find out much later and after much more work that it was.
You have a narrow band that is not great even when it is brand new. It does not give you any concrete data just that it thinks that the stream of all 6 exhaust runners are within it's parameters.
Could you have 1 cylinder with a bad injector so that it is running lean and the other 5 cylinders are running slightly rich and still have the combination of all 6 be within the range of the narrow band? Yes you could. Could you have a bad narrow band that is giving you false readings and everything is lean? Yes you could.
These are the kinds of things you need to start ruling out. You can get a wideband and check it, you could pull all the plugs and check them, you could pull and test the injectors, you could get the borescope like I mentioned and check the pistons.
Lots of things to do, I feel like you haven't tried everything yet, and you are kind of giving up on it without really looking into it. Rusco is absolutely right you can not rule out a Head Shops word that it isn't a valve. You have no idea how many times I have had people tell me it couldn't be something only to find out much later and after much more work that it was.
, I always get that backwards.
LFD2037
TEXAS LEXUS!
- Thread starter
- #199
IF it was valves then ambient temp would change if it rattled or not? The guy who owns the head shop (bad name. It's actually a mechanic/machine shop that specializes in head work) said ambient temps would have no effect on it if it rattled or not. Said one problem at idle and cool or another problem when warm. The ambient temp wouldn't be a factor, much less THE factor, in wether it did it or not. Hope that makes sense. You're saying ambient temp can 100% effect it happening or not if its valves? Thanks.
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.
