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1980 El Camino 4.4 ltr.... falter developed...
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akbolt
Novice
Sep 26, 2011, 2:14 PM
Post #1 of 12
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1980 El Camino 4.4 ltr.... falter developed...
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Thanks guys, here we go......... 1980 El Camino, 4.4 ltr...267 V-8..... 190,000 miles....... always runs great...new timing gears and chain 10,000 miles ago...... regular maintenence..... daily driver...... vehicle developed a "falter" a few weeks ago...... found bad gas in the tank, emptied as far as possible with a siphon attached to the supply pipe at the engine compartment, removed the carb and dumped out and cleaned....then rebuilt carb, very little carb wear, evidence of it being a replacement carb prior to my owenrship, (Rochester Dual-Jet)... no change....... new plugs, plug wires, rotor, cap, condensor harness, new fuel pump, new battery, new fuel filter, new choke pull off/ found old one leaking-replaced..... switched the ICM with an old one to see if there would be a change -negative........ lot's of time spent going over all of the vacuum lines, this "falter " doesn't occur till the engine warms up, then it's not a "full" falter.......rather like two or three plugs are switched off and turned back on again....... same on flats and hills.... we have hills around here at Hood Canal, Wash. state.............. distributor flyweight springs intact, vacuum advance diaphram works, could this be intermittent? This "falter" came on very slightly over 20 miles and stays at the current level now during testing and observation...... almost reminds me of a ignition switch going bad the way the car feels when running,,,,, "falter" occurs when warm just above idling when changing rpms and listening to engine with hood up....... thought cleaning the carb would clear out any passageway issues that affect the idle mixtures....... timing set at spec, idle air mixture jet seeming set properly........ got me and a paid mechanic scratching our heads....... next ideas....... fuel treatment if there's just a bit of crud left in the tank, ignition control module...... I always thought the gms usually just die completely unlike some others that act up before becoming unoperable....... hummmm???? thanks--- akbolt
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chickenhouse
Enthusiast
Sep 26, 2011, 3:09 PM
Post #2 of 12
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Re: 1980 El Camino 4.4 ltr.... falter developed...
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All I can think of off hand is the throttle shaft that goes through the bottom of the carb. A replacement carb may not have had the throttle shaft re bushed, causing a slight leak in vacuum. Tried bumping the timing a couple of degrees?
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akbolt
Novice
Sep 26, 2011, 3:33 PM
Post #3 of 12
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Re: 1980 El Camino 4.4 ltr.... falter developed...
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Thanks chickenhouse, looking at and considering the throttleshaft wear just before installing the carb kit.... I didn't think it was worn "enough" to affect anything..... did not look rebushed, now that I think about it nor did any bushing/color difference stand out..... the shaft had such a slight amount of play, I didn't think it a factor.... guessing just a couple of thousands, if that, ...maybe that's enough ?....... I have advanced the timing from 4 btc, in the past to compensate for the old engine, to about 8 btc..... runs better but doesn't get rid of the "falter"....... have tried altering this multiple times during this process....to see and feel for any differences........ thanks.... now what?
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chickenhouse
Enthusiast
Sep 26, 2011, 3:42 PM
Post #4 of 12
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Re: 1980 El Camino 4.4 ltr.... falter developed...
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Well, you say the vacuum advance diaphram is not leaking. Is it moving ok? Did you put a vacuum pump on it and verify the advance plate is moving? After that, all I got is in the carb.
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akbolt
Novice
Sep 26, 2011, 3:56 PM
Post #5 of 12
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Re: 1980 El Camino 4.4 ltr.... falter developed...
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That's my concern too...... I had pulled the hose and sucked on it to watch it move back and forth, but don't know how it works under pressure....steady or not......the flyweights are free and working. guess I need to get a tester...... The mechanic that I took it to said it(the vacuum advance) was ok and that he tested it with a vacuum tester....... probably a cheap and fragile part that needs to be replaced more often than a hundred thousand miles no matter what.......
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chickenhouse
Enthusiast
Sep 26, 2011, 4:05 PM
Post #6 of 12
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Re: 1980 El Camino 4.4 ltr.... falter developed...
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Is it connected to ported or manifold vacuum?
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akbolt
Novice
Sep 26, 2011, 4:27 PM
Post #7 of 12
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Re: 1980 El Camino 4.4 ltr.... falter developed...
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I don't know my "ported" from "manifold" vacuum.......... the vacuum hose "Y's" about two inches from the diaphram. The larger hose/tube goes to and is attached to the carb base on the drivers side.... the other hose is attached to the "temperature sensor" located in the bottom of the air cleaner body/assembly to which also is another hose attached to the hot air valve "vacuum diaphram motor" located in the air cleaner "snorkel" which opens and closes with heat and warming up.....
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chickenhouse
Enthusiast
Sep 26, 2011, 8:03 PM
Post #8 of 12
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Re: 1980 El Camino 4.4 ltr.... falter developed...
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Engine running at idle, if you take the hose off the advance, does it have vacuum? If so, that would be manifold vacuum. If none present, accelerate slightly and feel for vacuum. If it comes in then, that should be ported. Ported vacuum is above throttle plate, manifold comes off the intake.
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akbolt
Novice
Sep 26, 2011, 9:07 PM
Post #9 of 12
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Re: 1980 El Camino 4.4 ltr.... falter developed...
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Thanks, from the "looks' I'd say ported, but will test it first thing in the morn.......
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DanD
Veteran
/ Moderator
Sep 27, 2011, 8:57 AM
Post #10 of 12
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Re: 1980 El Camino 4.4 ltr.... falter developed...
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Just too jump in here with a suggestion; this running issue might have something to do with the EGR valve opening to early and or too much?
Back then they used either a ported EGR or a back pressure EGR; then there were two different styles of back pressure EGR valves; positive & negative.
A ported EGR valve will begin to open anytime there is more then 2” of ported vacuum applied to the valve and open fully after vacuum reaches approx 8” of vacuum.
A Back pressure valve also works within the same vacuum parameters but it also needs to feel exhaust back pressure on an internal valve with-in the EGR before it will begin to open.
The idea of the back pressure EGR is that a combination of engine vacuum and exhaust back pressure will regulate how much EGR should be applied. In other words slow down how fast it would open and how far it would open regardless of engine vacuum.
A ported EGR’s valve return spring would become weak or broken allowing the valve to open way too quickly and too far with a very small amount of vacuum applied.
The same with the back pressure valves; but they also had a problem with the small diameter tube inside the EGR would become plugged. This tube supplied exhaust back pressure to the EGR’s internal regulating valve. With it plugged the valve may not open at all or pop open at the slightest amount of vacuum applied.
When an EGR valve opens this way it causes the engine to go extremely lean during acceleration; which in turn could cause a hesitation/”falter”
Try un-plugging the EGR vacuum line and plug off the hose; now take it for a road test.
You can tell what type of valve that’s on your engine by the part number (if its not been changed with an after market) stamped on the valve.
If it’s a ported valve there will only be a part # something like 1704-----. If it’s a back pressure valve it’ll have a part number followed by a capital P for positive or an N for negative back pressure.
Sorry for the novel; but I wanted to explain so that if it was the problem you’d know why. This is if the intake is not plugged with carbon if so then none of the above would matter.
One last thought that I won’t go into (well not to far LOL); the camshafts were famous for wiping off individual lift lobes. I can’t remember the number of cams we replaced back then on the 4.4 and the 5lt engines; but it has to be in the hundreds and I’m just a small shop.
A quick test for that would be to remove the air cleaner, bring the engine up to temperature and then quickly crack the throttle wide open and closed. As the rpm begins to peak, you’ll hear a slight but rapid backfire coming from what sounds like deep inside the carb. Sounding something like a kids bike with a baseball card stuck in the spokes. If you hear that, pull the valve covers and confirm that all valves have somewhat the same amount of opening movement; if the cam’s gone it’ll be obvious.
Dan.
Canadian "EH"
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akbolt
Novice
Sep 27, 2011, 9:24 AM
Post #11 of 12
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Re: 1980 El Camino 4.4 ltr.... falter developed...
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Oh Wow, thanks for all of the info....now, there's more to do of course. I'll get back to you on these issues...... I did take off the egr valve to inspect it and the passageways were clean and not loaded up like I've heard about happening..... the egr itself was not particularly working freely, but didn't seem too gummed up and I just put a few drops of liquid wrench on the shaft to dissolve some of the carbon and it free it up a little bit....... hope the cam isn't the culprit..... but if it is it is...... thanks for your input....back a little later---
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akbolt
Novice
Sep 28, 2011, 10:21 AM
Post #12 of 12
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Re: 1980 El Camino 4.4 ltr.... falter developed...
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El Camino Update---------- Wed. morning ....... plugged off the egr valve on both ends..... made a 5 mile test drive..... no faltering occurred. The egr valve is marked ---- AAY 1706 2416 ...so it looks like from your description that it is a "ported" valve...which when I just took it off again this morning to reinspect the crud amount in the manifold.... there's no other "small" diameter tube inside the egr.......... now that I think of it, it seems in the past that I've seen the exact same hoses plugged off on other persons egr valves...... guess they already knew the trick and what to do....... .......... is there any preference on purchasing egr valves other than the local NAPA store or auto parts suppliers, car junky ......... as to quality ?? Thanks DanD and chickenhouse...... will update should any change occur....... hope the cam lobes are good ones.......... fingers crossed..... this is a nice driving old El Camino......
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