I’ve searched through all the forums and nothing has helped so far, which is why I’m making this new thread.

engine: f22a1 w/automatic trans, 283k miles

The symptoms: engine starts okay, slight tapping from valvetrain chatter and possible early detonation. As engine heats up idle drops below 1k and starts vibrating. Once operating temp is reached, engine shakes a lot. Barely tapping on throttle causes it to smooth out and seem fine. Anything outside of idle the engine runs fine, with the exception of occasionally feeling like its engine braking an excessive amount (intermittent, rare and random, no noticeable pattern).

What I’ve done: IACV replaced
EGR cleaned
headgasket replaced and cylinder head machined(pistons remained stationary when pushed in an attempt to test for bad piston rings)
O2 sensor replaced
coolant temp sensor replaced
fuel injectors replaced
fuel filter replaced
cleaned carbon out of intake manifold and throttle body
Replaced fuel pressure regulator
replaced multiple vacuum lines
replaced distributor (slight effect, engine starts better, but seems to run in an almost rotational vibration rather than constant)
adjusted valve lash
checked compression (145,155,162,150, left to right 4-1)

car was heavily abused before I got it, first few oil changes came with a sludge of carbon buildup, only recently got the last of it out. Intake manifold and throttle body coated in carbon. Timing was between 2-4 teeth off when I first got the car. Headgasket job had been butchered before I got it, hand loose bolts on intake manifold, exceptionally loose cylinder head bolts, torn vac lines, etc. genuinely surprised it ran at all. Extreme carbon buildup on anything intake/exhaust related seems to have been cleared with the exception of maybe the egr lines through the intake manifold.

ive been struggling with this car for over a year, literally anything you guys can add I would appreciate.

 

Did you check sparkplug condition and gap correctly?
What condition are the spark plugs wires in?
Are the spark plugs wells clean and dry?

I've had a new set of wires with a bad wire out of the box.
Also certain aftermarket wire sets do not have the boot molded correctly and do not provide a solid 'snap' connection.
Honda, Sumitomo, NGK, Denso, UMP(Packard) sets are quality.

 

Just checked spark plugs and wires. All function well. However the timing is apparently one tooth off on the camshaft. Is there some trick for getting the timing to be spot on? It took me four tries before I thought I had it last time, but evidently I was off.

 

Set timing correctly. Runs smoother with fewer noises than before, but still runs rich and has very rough idle under 1k rpm. Going to try to burp coolant and do an idle relearn for the running rich. Noticed cracks in harmonic balancer while I had it off, so going to replace that too I guess.

 

Which coolant sensor did you replace?

If the sensor is reading incorrectly the ECU may think the car is still cold.
Backprobe and verify the voltage output to temp reading is correct.

 

I replaced the larger sensor, with the 2 prong plug on it. Have verified resistance through the sensor is good, and voltage to the sensor is also good.

 

Update: checked resistance on the fuel injector resistor pack and it isn’t adding any resistance to the fuel injector circuits. There are no check engine lights though, which is a touch confusing

 

For certain items the self diagnostics may not set off the cel.

Are the injectors themselves the correct resistance or different?

 

The injectors are the correct resistance. Injector resistor box is doing its job. However there are 30 or so ohms resistance on the signal wires for the fuel injectors running on the back of the engine, and 60 or so ohms on the run going through the firewall to the ecu.

 

The multimeter I had been using was faulty, there is continuity on all wiring harnesses to the fuel injectors, the resistor box and injectors add up to ~13 ohms.

however the car sputters and almost starts but ultimately fails unless the ground wire on the main relay is interrupted. When in that state, it barely runs, and dies if I give it throttle.