2G Ignition Timing or something else?

[Spinner]

Hi everyone, I have a strange problem that i am running out of ideas and have tried everything i can think of.
I'll try to give as much info as possible.

Car: '98 gsx, stock basically some bolt ons.

Problem: it's odd I'll try my best to explain. it's running very rough and seemingly not firing in the correct order. it will fire and run on any one cylinder but not all at once. I can get a video later if needed. the engine fires up and runs when started, be it poorly, no check engine light. all of my friends also DSM/evo owners tell me it's the timing (see below).

What has been done: I have redone the timing and it is spot on. verified spark on all 4. listened for injectors, they seem to be functioning fine. I have a spare ECU and PTU i tried swapping those since it's easy, no luck there. cam and crank sensors are new. unplugged the TPS, no change to idle. the only other thing I can think to try is the MPI relay?

How the problem happened: This may be irrelevant but I'm trying to provide as much info as possible. i was accelerating at WOT and hit a fuel cut at 5k rpm (I understand what this is now and it is not of concern just the problem at hand is what I'm focusing on) while hitting the fuel cut, which lasted less than a second i would say, there was a distinct and sudden change in tone. lost power in 3 or 4 cylinders and this is where I'm at now hasn't changed from that state. i limped it home barely making it sometimes another cylinder would come back in fire a few times and go back out.

If anyone can get me in the right direction or suggest something to look into it would be greatly appreciated.

 

[DogWhistle]

When you verified spark, did you pull the plugs?

 

[motomattx]

Compression check first, you could have valve damage from detonation, it might not have been fuel cut at all, then boost leak test.

 

[spyve4]

Check compression, install new plugs. If you pull the injector plugs one at a time is there any that don’t change the rpm?

 

[Spinner]

Thank you all for the replies!

When you verified spark, did you pull the plugs?

I pulled the wire off the plug and checked spark there.

Compression check first, you could have valve damage from detonation, it might not have been fuel cut at all, then boost leak test.

I haven't yet compression tested unfortunately i don't have the tool for it. I thought the same thing about valve damage though there isn't any metal on metal noise I would think you would definitely hear if there was that kind of damage or am I wrong?

Check compression, install new plugs. If you pull the injector plugs one at a time is there any that don’t change the rpm?

i didn't think to unplug injectors what is your thought behind that? i listed to make sure they were opening and closing and they sound ok but the idle rps varies.

 

[BoostedBeaver]

Pull the plugs and see what they look like.... thats an easy task that takes just a little time.

You can rent a compression tester from any parts store to perform the test.

I would suggest pulling spark one at a time. Pulling fuel will have the same effect but the plug wires are more easily accessible. Pulling spark or fuel to any given cylinder should cause a noticeable change in operation. If you pull one or the other and there is no change, that cylinder is not working properly.

 

[AWD-Tony]

Try unplugging MAF and see if it changes. Or swap it with one of your buddies.