To: jeffzepp@earthlink.net
Date: Monday, February 25, 2002 9:17 AM
Subject: Re: misses & cats
I didn't say anything about malfunctioning carb. I said a lack of fuel to some or all cylinders. Fuel gets to the cylinder through a manifold, w/many potential leaks, through a gasket, which leaks, through a port, that may be carboned up, past a valve, that may be carboned up, and over a valve seat, which may be burned or misadjusted.
From my email to which he is responding: Of course that's true, but he checked for vacuum leaks, and the fact that it runs great at WOT and it idles okay would tend to discount those other potential problems, wouldn't it?
Jeff, I am writing to you directly, because my misanthropic diatribes are not easily digested by the rest of the list members. I have also gone direct to Reid, as he has expressed an interest in contracting my commercial services.
Again, Reid said he checked for vacuum leaks, but I had the feeling from his post that he was fairly inexperienced in the wrenching arts. I will assume that his testing/checking was not exhaustive. The engine is going lean in the midrange. There are only two things that can cause this: either the carb is malfunctioning (or being malfunctioned), or else a mechanical defect downstream of the carb is causing the mixture to go lean.
In my analysis, I choose to disregard carb malfunction for now (because this carb was tested on another engine & ran fine, and because Reid indicated that the symptom existed before changing carbs).
Some poor paraphrasing of Sherlock Holmes: "Once all other possibilities have been eliminated, whatever is left, no matter how improbable, must be the truth."
The idle fuel circuit is *always* flowing fuel. It is figured in to the overall mixture at all throttle positions. IOW, the correct fuel for the primary barrel at ~50% throttle is all the fuel that can go through the idle circuit, plus as much fuel as demand pulls through the main jet. Take away idle circuit fuel, and the carb dies at idle, and is lean everywhere above idle.
From my email to which he is responding: Ah, new factoid to stash away. I know you told me on the phone that the idle circuit is "separate" from the mains, but I didn't get it through my head that the trickle of fuel through the idle circuit is also applied under open
throttle positions. At this point, a reading of Reid's plug(s) immediately after the problem occured would probably be helpful, no?
Good point. An old fashioned reading of the entrails, *When the symptom occurs*, can give clues to what is actually happening in the engine.
"If he is trully desmogged"... Not seeing the truck, I have no idea what horrific surgery has been done to it. IMHO, a truck is only properly desmogged if I have done it. Anybody else's work is suspect, until I have checked it. I say this as a person who spends hours on the phone every day talking people through correcting the messes they have created themselves, with good intentions and bad information.
From my email to which he is responding: Good point, I have seen a lot of hack jobs also. Mark's follow up was gave me a good grin :-)
Yes, and my comment and Mark's example is just the tip of the iceberg of ignorance. {8^0
Again, many owners tell me their trucks are desmogged, but run badly. I ask how they dealt w/ removing the evap and still allowing a source of filtered air back into the fuel tank. Silence. "You mean the canister thingy does something?"
And so you can see that I must always *assume* that the desmog is a hatchet job, until the facts prove otherwise. Guilty until proven innocent.
From my email to which he is responding: Now would be a good time for Reid to elaborate in greater detail as to exactly how his 60 is desmogged, what is hooked to what, what isn't hooked up, what's present and what isn't. And hopefully by now the PCV has been verified for proper connections/operation.
Reid and I have gone private w/ his particular issue, so he has the benefit of direct communication w/ me, and I might get paid for my services. It sounds like he has most of the desmog done correctly by my standards w/ the help of he Rich Adams smog diagram.
Maybe a chunk of something floating around inside the carb. That explains the fact that symptoms are not always present. If the computer is still doing something, that could also explain intermittent symptoms.
From my email to which he is responding: Time to pull the air horn and take a peek inside the bowl? Where else would he look for debris that might cause these symptoms?
Yep, that's generally where it's gonna show up. Or at the bottom of the slow jet well. It looks like Reid is gonna send me his original tired carb for treatment, so he can give back Rich's borrowed carb.
Thanks,
Jim Chenoweth
TLC Performance
Lancaster, Ohio, USA
Ph. 740.862.2604
TLCA #1914
From: FJ40Jim@aol.com From my email to which he is responding: Since he had never checked static timing, let alone smooth centrifugal advance or proper vacuum advance, and having experienced first hand how each of these timing issues can cause crappy running, missing and so forth I thought that this would be the best avenue to explore first. I stand corrected! One other thing that you don't know and I do: The 81-87 distributor is a work of art. The shaft spins on sealed ball bearings, the breaker plate advances on a proprietary large ball bearing ring, the weights pivot on teflon inserts, the distributor is sealed against dirt & water contamination, provided with a source of fresh, clean air.... These late model ditributors don't fail. By contrast, the early (E-74) points distributors are a Toyota improved copy of a Delco distributor, and as such, they are crap. Subject to leaky retards, sticking braker plates, eroded weights, worn shafts & bushings.... What does fail on the late model trucks is emission system parts & function and the old bugaboos of various vacuum leaks. That's why I was approaching his problem from the angle I was. Thanks, From: FJ40Jim@aol.com From my email to which he is responding: Which brings me to a question I do not know the answer to and you probably do. The question is regarding the dual vacuum actuators on 78-up electronic distributors. I know that the 78 vintage is smaller than 60 series in diameter, has only one port in the cap for fresh air instead of 2, but I do not know for sure what vintage does what. *I have heard that 78-79 or so is dual advance/retard. *I have heard that all dual USA spec is dual retard (I don't believe this) *I have heard that all later dists are dual advance, with one being a little (like 4° or so) and the other is more (like 7-9° or so). Here is the real deal on 49 state US distributors from the beginning of time. Post this on a webpage somewhere so I don't have to repeat it. All E-87 have mechanical advance. Curves vary from year to year. E-'68: Xtra small distributor, vacuum advance (correctly called "non-smog", also sold as "non-USA"). 69-74: XS distributor, but w/ vac retard. 75 & early 76: small distributor, completely redesigned, very good quality points distributor. Vacuum retard. Late '76 &77: Same, but w/ vac advance '78: redesigned w/ Med. size screwdown, waterproof cap, electronic ignition. Vacuum advance & retard. '79-80: dual diaphragm advance. One big advance stage for normal operation, small second stage for extra advance at hi-altitude 81-87distributor body redesigned to use large cap. Same dual diapragm advance introduced in '79. 88-92 distributor redesigned w/ out advance. Distributor pickup is a crank angle sensor, advance curve is controlled by computer. That's all I know (or all I'm admitting to) for now. Thanks,
To: jeffzepp@earthlink.net
Date: Tuesday, February 26, 2002 10:07 AM
Subject: Re: misses & cats
Jim Chenoweth
TLC Performance
Lancaster, Ohio, USA
Ph. 740.862.2604
TLCA #1914
To: jeffzepp@earthlink.net
Date: Wednesday, February 27, 2002 7:42 AM
Subject: Re: was misses & cats, now dists
Jim Chenoweth
TLC Performance
Lancaster, Ohio, USA
Ph. 740.862.2604
TLCA #1914
