Ive read through lots of fourms and finally decieded to post, as Im at a loss... I have a 1983 Toyota Landcruiser with a 283 in it. Not sure of the exact year or donor vehicle, but it was confirmed off the back of the block. I have had the car for about 2 years. I purchased it already swapped and it ran fine at the time. Recently it has had some issues with surging under load, and particularly up gradients and some hills. Or sometimes with a hard acceleration and then any moderate or hard throttle imput would just make the engine die out and stumble hard. I could pull over and let it idle and go to 4-5k no problem after though. I thought it could be secondary air valve out of adjustment, but it would do it most often just with primaires engaged. Sometimes at 30mph, sometimes at 50. Simple adjustments (float levels) did not make a marked difference and it wasnt consistent, so i started throwing parts at it. New hydraulic lifters as it had a light tick and just wanted to clean that up. Next was a new Edlebrock AVS2 500 on it (had an AVS2500 and local mechanic sad put new one on and try again Then a new hei cap, coil and rotor. Newest part was a carter fuel pump (M6624). Nothing fixed the miss. After the pump i started questioning the fuel line routings and tank vent lines. Turns out they had a 3 nipple filter plumbed in and the return was plumbed to the vent line. And the actual return line was capped with a bolt and left out in the breeze. I remedied it to be properly hooked up and now the car wont run. Itll turn on, and idle for a few seconds and then randomly die. Didnt do this at all before i swapped lines so i clamped the return shut. Still acting up and dying. Im lost, so im open to any thoughts, concerns, critisism, etc. Just wanted some help hopefully. Thanks!
^^^^^^ This happened to me once. I threw ALL KINDS of parts at it before 'just changing the fuel filter" (it was one of those glass cased ones and the filter medium looked GREAT!) Another bone-head move I made was to 'sling parts at it' until I put a new battery in and PROBLEM SOLVED! I guess the old battery didn't have a full charge and although it cranked the engine....when it was 'all-wrung-out' in second gear it would miss and stutter until I let off the gas. Then it ran flawlessly under 4-5000 RPM. Check the cheap stuff first. Like 427 sleep sez....hook it back up the way it was...and start over.
First a really quick story on my personal experience, I once had a low mileage 1973 Lincoln I bought it for pennies because the guy could not figure out what was wrong with it. It would rev just fine in park as soon as you put it in gear and gave it just a little gas The car would sputter and cough and stall. After rebuilding a carburetor replacing every piece of the ignition system my buddy came over while I was cranking on the car and he saw a little itty bitty arc on the coil power wire right where Ford had those 90° push-on terminals that slide right over the threads... Anyways long story short I cut that off put a ringlet on it and The car ran like a champ and it was all because the ignition coil power wire was not making a real good connection but it did have a connection nonetheless. Now onto your 'yota That was opted with the small block Chevy (It's a joke It seems like they all have small blocks). You said you went through the fuel system so we can rule that out as the problem. I will almost guarantee you it is an ignition problem. First thing I would do because it's free just make sure all you're wearing connections are good and when I say good I mean tight like there's no loose connections. If you believe all your connections are good I would guess it is probably the ignition control module that is down in the distributor, very rarely is it going to be the magnetic pickup but those too can go bad You did not state which HEI you had but I'm going to assume it's the big cap from the '70s. Anyways here is the link on how to test the GM HEI as usual the hamb comes through https://www.jalopyjournal.com/forum/threads/is-there-a-way-to-test-an-hei-module.706237/
Atomic Reverend Alexander might have nailed it with the magnetic pickup, wires on the pickup are flexed every time the vacuum advance plate moves, sometimes the copper in the wires break from use and lose contact when the advance plate moves, causing the same as you described. Try disconnecting the vacuum advance so the plate remains stationary, if drivability improves replacing the wires or the whole magnetic pickup should solve the problem
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