4age hitting gas too quick means engine stalls - what is the issue?

[Ryo]

Hello
I am unable to figure out what can be the issue on my ae92 with early tvis red top 4age engine with AFM. I know i got fuel i got spark and when i start the engine it revs with about 1500rpm cold. But this all not matter as i am not able to get the engine to higher rpm quickly hitting the gas i can do it only very slowly. Hitting the gas too quick means engine stalls and mostly dies. Am i looking for a vacuum leak or air intake clogged? I don't know which things actually affect this. I asked on boards elswhere and studied manual measured things around checked hoses but no luck. This is one tricky issue. Anyone has some idea where to look. AFM looks operating normally and throttle body was cleaned as well last time.
Thanks for any hints. Ryo.

[jondee86]

Probably the ignition timing is too far advanced. Check the
ignition timing (should be 15-17 degrees BTDC if you DON'T
bridge the diagnostic plug, 10 degrees BTDC if you DO bridge the
diagnostic plug).

Cheers... jondee86

[Ryo]

I don't think the issue is there we already tried this. And we already know that disconnecting any vacuum hose have not affect on the issue either. So i am lost what to check now. How should i proceed further? Also i forgot to mention that if i start the engine it happens that it get to 1500rpm and than it slowly stalls to zero unless i move on AFM the flap. Not sure what this means. But once i get it to stable rpm and hit the gas quick it just hesitates. Slowly going to higher rpm is ok. I don't have any special measuring things so i have no clue if i got right fuel pressure or if the engine got good compressions fact is it sucks air really strong so the flap on AFM should get open automatically without my help. I was not dismantling air inteke manifold to look for butterfly valves condition but if you will say the issue might be there i will try to clean it. Just have no idea how much this affects the existing issue.

[jondee86]

When you start the engine from cold it should go to around 2200rpm and then
slowly drop down to around 900rpm when it reaches operating temperature. You
could try raising the warm idle speed by opening up the idle air bypass screw (down
the tube on the side of the throttle body). See if that stops the stalling.

The next thing to check is to make sure that the IDL switch in the TPS is changing
state when the throttle goes fully closed. The adjustment procedure is in the FSM
and you will need a set of feeler gauges and a basic multimeter. You can also use
the multimeter to check that the TPS is sending the correct signals to the ECU.

The AFM is the primary load sensor for the ECU, but the TPS is important for idle
and the "accelerator pump" function when the throttle is opened quickly.

Cheers... jondee86

[Ryo]

Any other hints if i found nothing that this is affecting it? I bet my findings will be nearly zero success anyway. The car was working perfectly until was moved on long stand to garage. After some long time they decided to start without luck. Than i was taking the car.
Removed the fuel tank discovered it was rusted out possibly because of that fuel pump died.
Replaced the tank for a brand new replaced pump for used one from ae86 new hoses new fuel filter. Replaced rubber seals on injectors because of fuel leakage. Moved engine wire harness to correct place (was on top of the fuel rail for some reason). And yes all is connected as it was before when i moved it i verified twice.
One thing i was doing in addition was cleaning of rust charcoal canister so disconnecting cleaning and putting it all together. No rust dust possible all what i dismantled was cleaned with compressed air or other way. After this i was first time starting the engine and this issues appear. So i was not touching afm or tps or anything before just now i cleaned throttle body because i was looking where the issue can be. There is really lot of hoses and swith sensor stuff that i really don't understand it looks little bit different than on my ae86. I wish there was less electronic and vacuum stuff as it is really confusing for looking at it what can cause such large issues. I will have time to look on the car again next week possibly so i must have some plan how to proceed further. I am starting to ask myself if this was all worth the trouble to be a hero and saving the car from being dismantled on parts.

[ZDoman]

You should check the big rubber pipe between the throttle body and the AFM. This is used to tear/crack. You should have enaugh vacuum at the AFM to move the flap by the engine itself.

[jondee86]

Have you driven the car ??
Have you changed the fuel filter ??
Have you checked the fuel pressure/flow ??
Was there rust in the fuel rail ??

When fault finding, you can only deal in facts. Not guesses or something the
previous owner told you. As Sherlock Holmes said... "Once you eliminate the
impossible, whatever remains, no matter how improbable, must be the truth...
elementary my dear Ryo".

[Ryo]

My apology i released too much of my feelings. I am glad that you are helping me guy's. Yes you are absolutely right jondee86 i will be more precise with my investigation from now on to find the issue.
To answer your questions:
- No i was not driving the car i was taking it from my friend with non drivable condition.
- Fuel filter changed for a new one (Filtron brand) for exact type for AE92
- I was not able to check the fuel pressure as i have not measuring tool for that. I checked for prices on those and they cost too much to buy. Is there some workaround possible or should i try to borrow some (perhaps someone will have some but not quite sure).
- There was no rust in the fuel rail (in fuel) as i remeber when i was replacing the rubber seals on the injectors. Can be that i exchanged on some position but they look all the same.
First time when i started the engine i remeber that some pipe was leaking near the fuel tank but i managed to seal the leak. Of course i can't tell if the fuel pump from AE86 i installed is giving enough pressure as it is a bit old (but was working in my AE86 properly after i put it out and in box on shelf... was sitting there for longer time). I would like to properly investigate the issue from now on but i would like to create some plan how to proceed step by step to troubleshoot this.

[allencr]

When the throttle is increased slowly, it can go to 5-6000rpm, right? Then I think that the fuel pressure is OK.

Wiring loom injector grounds bolted under the intake manifold?

[jondee86]

If you cannot drive the car then it is not possible to put the engine
under load. If there is a restriction to flow in the fuel line (kinked hose,
flattened hard line or partial blockage) it is possible to have good pressure
at idle but low pressure and fuel starvation under load. A fuel pressure
gauge can be used to check while the engine is running, as opening the
throttle quickly puts load on the engine for a second, and the gauge will
drop if there is a problem. But we can leave this until later

First you should check the engine timing in this order...
1. Take off the top timing belt cover and check the dimples on the cam
pulleys line up with the marks on the backing plate. When the marks are
lined up, make sure that the engine is at TDC (timing mark on crank
pulley at zero degrees on the timing scale marked on the bottom timing
belt cover). If the marks do not line up you will need to adjust the belt.
2. Check and/or adjust the tensioner for the timing belt if the timing belt
is loose. You will need to be able to turn the engine by hand using a
socket on the crank pulley bolt. I don't know if this is easy on an AE92 ?
3. Check the ignition timing with a timing light. You need to be able to
keep the engine speed steady at around 850-900rpm. DO NOT bridge the
diagnostic plug/box). The timing mark on the crank pulley should hover
around 16-17 degrees at idle, and increase with engine speed.

Once the engine timing is confirmed to be correct, if the problem still
remains we can look at other possible causes.

Cheers... jondee86