Fuel injectors or damper?

Do this: start the engine cold. Then, unplug the IAC pigtail. If it instantly stalls, the IAC works when cold. Now, plug it back in, restart it, let the engine get to temperature with the hood down (to hold the heat in). When it's good and hot, lift the hood, unplug the IAC. If the engine stalls, the IAC is good, and you have another problem. If it doesn't stall cold or hot, replace the IAC.

 

Um I set base idle at the point of engine would run on its own without IAC, read that on one of the many ways to set/relearn idle. So then by what you’re saying, I’ve set up idle wrong………

 

Yup. I do not ever listen to anyone else on idle, as I've learned the hard way, their directions don't always work. Whether a carburetor, throttle body injection or port injection, the throttle plates are supposed to be set so that the plates are just about at the point of hanging against the bores (or, "plate is just...against the bore" for port injection with one plate), then the TPS voltage needs to be read at KOEO....should be .9V (spec calls for .65 to .95, but the higher the reading at closed throttle, the better), and if you can't adjust the TPS, do what I did--use a needle file to allow adjustment on the TPS. Then make sure the TPS works correctly by doing a full sweep of the throttle, slowly, to verify the signal voltage isn't lost at anytime between .9 and >4.5V.

 

So per your explanation. Idle no load 500-520. In gear 500. Ac 450-460. Both 470. Engine isn’t bouncing, running smooth. Sounds very slow tho…….

After this test, it tried stalling. Unplugged IAC, set idle at 550ish via screw. Set tps .94-.95. Turned off ignition. Plugged IAC in and cranked. Tis holding a lot better. The fully loaded idle is still a bit low in my opinion, but it’s holding between cranks and driving around block

 

Good. We're making progress. I had an '87 CV sedan, the IAC quit, stuck in the high idle position, it took a couple weeks of driving to get used to the new IAC fully. So just drive yours, let the PCM do its job, and in mid-month, you can report back. If anything goes wrong or you have any questions, don't hesitate to PM me here.

 

Cranked up beautifully this morning. Idle under load much better. Drove around the block to get ‘er hot. Yes PROGRESS! Def give a mid-month update

 

Huzzah!

 

Tis mid-month enough. Computer has learned ok. Fully loaded it runs at 500. It sometimes jumps from 520-470. But doesn’t stumble like it wants to stall. Had some cruise control issues that the computer was causing. Doing a MAS conversation requires a MAS speed amplifier. The computer needs to see vehicle speed to prevent too low of rpm whilst slowing, down shifting and all that jazz. My 85 controller would surge like 10mph with cruise plugged in to computer. But now I’m back to fuel issues. Fuel pump has been checked. Fuel filter changed. Every joint/connection checked and new seals. Inspected and changed FPR. looked as best as I could at the rail, nothing. Removed all spark plugs, none wet. Cycled fuel pump many times with plugs out, stuck pipe cleaners in each cylinder, no gas smell. Installed an external check valve on supply after filter. No change. Pressure still drops. I have to cycle the pump 1-4 times after sitting over night to crank. Gonna remove the upper intake to get unobstructed view of the rail. And if need be, remove injectors to see if one is leaking. But pulling hair over this one

 

Okay, this one's a bit simpler to tackle: have you installed a FP gauge on the rail, to observe post-shutdown pressure? The factory spec is, upon shutdown, rail pressure is 30-45 PSI, and must hold steady with no drop for two minutes, then no more than a 20% loss over eight hours. The regulator closes upon loss of vacuum, and the pump has a built-in check valve. Both are supposed to trap the supply line fuel, as well as zero leakouts from the injectors. I'm guessing you don't smell fuel after shutdown, and you should not; otherwise, you must not run the engine till the leak is fixed, as high-pressure fuel spray ignites so darned quickly. Ask me how I know. Anyway, having the gauge installed also would allow you to see just how long the pressure rises during cranking. Remember, upon KOEO, the pump cycles two seconds; then on CRANK, the pump turns on, and stays on when the ignition switch goes to the RUN position when the engine catches. Take a look at all that, and let me know what you find.

 

The gauge will go up to 35-40 after a couple of primes. It goes to zero in about 30 mins. Do not smell raw fuel. Do not see any leaks. Currently. The damper was leaking a few weeks back, but I deleted it

 

Hmmmm. Thirty minutes to go to zero is definitely a problem. Because the non-steel fuel line segments are nylon, they can't be crimped. The way you normally tell if the pump or FPR on EFI is leaking down is to block the return line. Most cars, you can crimp the return line, but not here. If there's a spare segment of steel return line that can be sacrificed to make a blocking plug to fit the return line connector at the tank, you would install and lock the plug in place, then cycle the key to get the pressure above 30 PSI. Remember, since the return line's blocked, the pressure becomes a "deadhead" pressure, so make sure you only cycle the key enough to get it to operating pressure. Otherwise, you can split a line or blow out an o-ring. Then watch the gauge. If the pressure still drops, the pump may be bad. I need to look in the manual to see if the pump or damper is the "check valve" in the tank. The only suck to this is you have to drop the tank to access the pump connections. But it may solve this problem, and if the pump end is bad, you're already ready to pull the pump.

 

I’ve dropped the tank about 10 times already trying to solve this. But I can block the return line at the rear wheel tomorrow. The pump does have a check valve, and then I put one just after filter, and yes it’s in the right direction haha

 

The pump's check valve does no good, if the top of the pump, the output line connections, or the steel line it connects to, don't hold pressure. It can leak while running and you wouldn't know because it's in-tank. It, however, would be the first car in 20+ years that had an in-tank leak that I've "dealt with," meaning that I'm attempting to help you with. And I forgot there are line connections for the tank at the frame rails, so hopefully it'll help narrow this all down.

 

That was one of the first things I checked and replaced. The new pump had a cheap clear plastic pipe coming off the pump to the pump flange. I put on a strong injection hose on and tightened the crap out of the clamps. But, for all we know, yes it could of come loose. I do appreciate all your advice and help. Post an update shortly with return line plugged shortly

 

Good to hear; you're quite welcome as I'm always happy to help, if I can. I'll shut my trap now, and be standing by.