Sabino56, although I can't remember the numbers, fuel pressure was better after the new pump. Honestly I think it was a waste of time, pressure was right around 10 with the old pump, I think it was 13 with the new (although now it whines every time I start the car) new pump was not my first choice in manufacturer... Yes new fuel
filter.

I've just straight disconnected the knock sensor to see if it was the culprit, but the answer is no, it doesn't change anything.

At this point we've pretty much ruled out Fuel or Air in the equation after a intensive rebuild of the TBI w/ new quality injectors, regulator, new pump and filter no other issues noted.

All the parts on the spark end of the equation are new, and spark has been confirmed at each cylinder.

I guess I'm not enthusiastic about an OBD1 reader as I'm fairly skeptical that it will really gather useful information. Also, I don't own a laptop. I might be more interested if I get around to doing any tuning, but right now I'm just trying to get the damn thing to run. Maybe the route to go would be to see if anyone had a setup in town. Definitely cheaper than buying a setup for a one-time use.

The reason I think the compression test is important is that A the compression is low in general and B two cylinders are on the verge or on the outside of %10. My understanding is that If the compression is low enough or the differential is high enough compression can either not occur or occur at the wrong time.

Analyzing Ignition Misfires

Hopefully tonight I'll be able to do a recheck with some squirts of oil and come back with that info.

 

Even though that's outside of 10%? My understanding is that 130psi is low to begin with. But I would think a damaged ring or a burnt valve could cause a vibration?

 

its only 10.7% off but as long as theyre uniform it just a worn engine due to normal ring wear.
did you test like this?

Warm the engine up
Remove all spark plugs
Disable the coil
Install a battery charger to maintain consistent cranking speeds.
Install your compression gauge and crank the engine 4 compression strokes on the cylinder you are testing.
Make sure you have the throttle wide open and the chokeis open.
Record your results for each cylinder.
If there is a difference of more than 10% between cylinders, perform a wet compression test.
Shoot a squirt of oil in the spark plug hole and repeat the test. Record your results.

imo if the rings were bad you either would have a blue smoke or if theyre that bad youll have a dead cylinder,

 

thanks for update - when I had problems @ idle the fuel pressure was around 10psi and replacing with pump that provided 13psi solid even under load resolved my problems, returned performance. So, even though it didn’t unfortunately help you current problem, I wouldn’t feel it was a waste of time. It definitely needed to be replaced.

sorry I don’t have other ideas to help - I have hard time seeing how low compression would intermittently cause problems @ idle but no experience on that so I can’t advise there. Good luck

 

Everything but the battery charger, and honestly, it's a massive battery stuck in there...

I ran out of time last night to re do the whole engine, but I rechecked the lowest cylinder which had been at 116 but started at 125 last night... Maybe the ring is moving around or maybe temperature was just different enough. But shot some oil in to it and it went up to 200psi..... 60% increase.

I guess ideally I'd do this on all 8 cylinders and see what % change is. Really I just want to make sure I don't have a totally borked valve at this point.

I don't recall if I asked specifically, is there a reasonable way to check the wiring harness between the ECM and the distributor? If the issue isn't Mechanical, that's kind of the last thing I can think to check

 

Did you ever clean and inspect the grounds? Just doing a visual won't do anything. Gotta clean them up since you have to take them off anyway. Even the battery connection.

 

Sorry for the slow reply, yes Irish, I cleaned all but the one next to the fuel tank thus far. Haven't had time. My theory is if it comes apart, it gets cleaned repaired or replaced, I'd never run a successful shop lol.

Still haven't had any revalations, except further confirmation that when the engine is hot, i intermittently lose a cylinder

*Update, that ground turned out to be the static line for the fuel tank and a ground for the trailer wiring harness, so no miracle there.

 

Update;

Thanks everyone who provided input, this has been a frustrating adventure so I figured I'd share just incase anyone else is having the same issues.

I ended up going back to the same shop as before (round two) and this time they identified that one maybe two of the spark plug wires were bad after making several other small fixes for problems they claimed to have found that made no change.

did the plug wires asap after I got it back and lo and behold it was fixed.

Kinda beating myself up on this one, because I had considered trying a new set of wires just for giggles a few months ago, but because I had put a timing light on each wire and "saw" spark and they were a reputable brand that was brand new I dismissed this flight of fancy... lesson learned. After you do all the obvious, checking it all again is sometimes better if you dont have a mechanic you trust.

Frustrated with the shop and the parts supplier. At least I got a refund from RockAuto for the part, dont think its reasonable for me to have to pay for shipping for a part they supplied that was faulty... but such is life I guess.

Also, if you were ever thinking about it, dont accidentally strip the nut on the fuel return line where it goes in to the tbi when you go to tighten it when the "real" mechanics leave it loose along with your feed line and cause drain back and leaking... that part is discontinued and you'll have to go to a breaker or your local rubber shop and have one made.

Sounding like every bitter home mechanic ever but o well. Running good now!!