s4 na starts idles but dies when you hit the gas
 

As the title says I picked up an 87 na that was doomed for crushing that's complete it just had some running issues, its ugly but its got a racing beat header, but the exhaust is open after that lol. After some tinkering ( deflood, dried plugs, cleaned grounds, fresh gas, oil change, charged battery I got it to start lol, dam this thing is loud. Its kinda wanting to die at first but you can give it gas to rev it up to like 2 k and then it'll hold an idle after like 10 seconds no problem, the car however does not like any throttle it backfires and wants to die if you give it any light gas or won't go over 2500 lol . Any insight? Im thinking maybe fuel pump but I dunno thanks

Bump for any insight, I have an 88 that was running great but grenaded an apex seal so before I swap everything from one motor to the next im trying to get an idea of what to try first, im also wondering if no exhaust on it is making a difference or not

It shouldnt be the exhaust,ive ran my car with just headers and its crazy loud lol ,it could be the primary injectors?
Secondary injectors kick in after 3800 rpms if i remember right.

this is weird, i was messing with the car replaced the fuel pump and fuel filter, did some tweaks and i hear a strange buzzing coming from the engine with the key on...i can't locate it it sound like its dead center of the engine bay lol , also the tach is stuck at 3k and now won't crank over at all, did my battery just blow up or what? i feel like this car has some wiring gremlins, how hard would it be just to swap the good keg and trans into the better looking car i have that has a blown apex seal but ran great before it died, so i'd be keeping all the same sensors/wiring etc

What... Wierd, ive never encountered something like this, try using a bigger battery, did you check again if your spark plugs are clogged or anything?
It could be the wiring, it could be anything.
You could do the swap and keep the other wiring harness from your blown motor, and while your at it replace all the vaccum hoses,if they have leaks,which could also cause the idle to rev up and down

yeah im thinking if i can just swap the upper intake manifolds with everything else attached to them including the wiring and get it running ok that would be ideal, save me the trouble of ripping the motor out of both cars right? its so frustrating because the one car ran great, just blew a seal, this one runs but not great lol im just trying to make it all work great again

Buzzing in de engine bay is your BAC-valve, thats the only thing that buzzes when its not running.

Check that the timing correct is.

If you have a vac leak the car will die under 2k, been there done that, had a mayor hole in the intake didn't see it when I rebuilded it. How yes and no exhaust at all, only a standard manifold is connected to the engine.

It's sounds like multiple Issues. How long has the car sat before you got it started? It may have some bad gas and needs to run for a bit. If it dies when you try to floor it,its ur ignition coils are going bad,also a reason for ur tach to.jump or stick. If car does start and run don't give up.on it. Hate to hear that a good rotary get scrapped cuz no one knows how to work on one. Happens all the time. Floods and goes to the bone yard

It seems as if you do have a huge vacuum leak. Follow from the maf to the intake. Also don't touch ur timing plz. It's rare for a rotary to JUST go out of timing

Don't think its a vacuum leak, like a said I had a vac leak in the manifold and over 2k it runned, under it died.

Check if the ecu give error codes.
You don't know what the previous owner has done to it so if necessary check it.
Could be a bad tps.

and compression test.

Did you change the sock on the base of the fuel pump? This is really a big cause of frustration, put a new one on, they are only 12 bucks each, if I remember right.
Not mentioned in my Haynes manual

Here's an update, electrical thing was my battery being shot lol, unplugged the tps and it seemed to start easier, still same problem, tried to just rotate the crank angle sensor at that point too to see any difference and no. So I started dismantling both engines, took off the uim from the problem motor, in which it seemed like has been removed before and the gasket was not too great, also the ecu groundlooked kinda corroded, cleaned a spot off for it, also the ecu harness near the plug I noticed a few wires cut lol jesus, so I swapped wiring harnesses from the cars and the 88 had different injectors without a resistor box so I swapped those too. Ordered a gasket from Mazdatrix so im just waiting on that to reassemble everything and see what happens, anything else I should make sure of while im waiting? I have not replaced the fuel sock that shouldn't be too hard, is there anyway I can confirm the timing on the cas? Po sprayed the engine bay red and got the pulleys too so I can't see the mark, will it be visible if I strip the paint?

Also on the passenger side of the 87 intake, there's some thing that had a vacuum hose connected to it, the 88 isn't even cast for it, upon further inspection im pretty sure the hose that was connected to it lead to the rear washer fluid container...wtf maybe that's why it was running like shit, who knows

Omg what did they do to the car :o

Normally if you remove the paint it can be visible.

I know seriously lol ok ill remove the paint tonight and see what I find

Normally where the marks are is a cut in the pulleys where the marks are.

If it dies under 2k couldn't it be the ecu?

it dies over 2.5k, itll idle all day below 2k, i think once i get this thing its gonna be money, im excited to drive it lol, hopefully this is it, pretty sure it needs a thermostat too when it was running i never felt the top hose get warm, waiting on the gasket, block off plates and ill pick up a thermostat too and go to work hopefully itll get here this week