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Just wondering if anyone has ever seen or heard of a lifter that bled down and caused an engine miss for say, the first quarter mile....before clearing up for the rest of the day....yet no clacking or any other noises were heard from under the hood?
Understand. Just curious because in this case I have an engine (Chevy 350) that when you fire it up cold, it'll idle and drive fine but has a noticeable miss both when you accelerate and at idle. It's not until you drive for a quarter mile does the miss go away, and doesn't come back until the engine has sat overnight w/o being ran. Also if the engine idles for more than 5 minutes the miss mysteriously goes away.
Only two things I can think of is either there's an ignition issue or a lifter is bleeding down. However I started the engine while cold and did the water trick on both exhaust manifolds where the exhaust ports are, and all 8 cylinders are firing.....yet when you start the engine while cold, there's no clacking that you typically hear with a leaked lifter.
FWIW the engine only has maybe less than 20k miles on it, it was rebuilt back about 1982 but was used as a DD until about 1988, then it was reverted to a weekend car status.
An easy way to determine if there's a miss in this engine would be to get it on a automotive scope with inductive pick-ups ...
you'll be able to identify the misfiring cylinder on a first start of the day within seconds, especially if it is an ignition problem. you could then verify a given cylinder as the problem when it's misfiring by shorting out that ignition; ie, remove the spark plug connector from the plug and ground the wire.
you might be able to pinpont a collapsed lifter by removing the valve covers and cranking the engine over. you'd be looking for the rocker arm which noticeably didn't move as much as the rest of them.
in theory it is possible, however i think you have a lean miss when cold. once the combustion chambers warm up it goes away. i have had that happen in the past with other engines.
It's a long-shot, but every once in a blue moon you'll have a spark plug that doesn't fire properly until it's in the proper heat range.
That said, yeah a lifter can bleed down. It's rare, and it's even more rare that you wouldn't hear the signature tapping sound that would accompany it.
When in doubt, I always look for the cheapest fix first...
Assuming a multi point injection system, my money is on an injector going bad. It's bleeding down a lot over night and it takes it a while to finally clear itself. Might consider a healthy dose of Techron in the gas. Techron is a PEA and a Stoddard solvent based cleaner. Those are the absolute best injection system cleaners there are. But even Techron has limits to what it can fix. I'd run the tank down to a half and throw in 2 bottles and drive it until near empty. That's a cheap fix.
If you think it's a lifter, drain one qt of oil out of the engine. Replace with one qt of G Oil 5w-30 found at most Walmarts. It has tons of solvency in it and has the highest detergent package available. That package FWIW is higher in cleaning than most engine flushes but it doesn't strip lubrication like a flush will. It CAN even fix seals that are weak. It's a polyol ester based oil, the only 100% polyol on the market. Polyols are used by a lot of the synthetic formulators for seal swell agents. Another cheap fix.
aren't there any shops around you with old timers still working there who know what to do with that old sun scope (or equivalent) that's been gathering dust in the back room storage area for the last 25 years?
the type of running problem you describe was what these diagnostic tools were made to analyze.
even a manifold vacuum gauge would be a helpful item for diagnostics at this point rather than guessing a hard mechanical intermittent failure.
you might even want to try checking for a cold intake manifold vacuum leak, which might be located with a propane torch as the source of fuel .... used to even use these on early emission carb'ed engines to enrich the mixture to meet the emissions test standards.
as I've mentioned on other threads, even Snap On Counselor II's are sitting around, available for cheap on places like eBay ... I bought my last one a few years ago for the roll-around cabinet it was sitting on for $25. All complete, all the accessories in the drawer, all the cabling ... even the manual was in the drawer.
as mentioned above, a collapsed lifter without the usual clatter would be possible, but very rare.
aren't there any shops around you with old timers still working there who know what to do with that old sun scope (or equivalent) that's been gathering dust in the back room storage area for the last 25 years?
the type of running problem you describe was what these diagnostic tools were made to analyze.
Nope....all the old timers can't remember anything, and the newcomers only know how to read what a machine tells them. The vacuum was good when I checked a few months ago, but good call I'll check again.
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