reoccurring hesitation?

[purrfektrs]

So I have an 87 325es. '885' head, but other than that, it's completely stock with a msd box.
I've had a reoccurring issue with the car since I bought it last year . The issue is that the car is what I call "temperamental " . What I mean by that is it runs fine then decides to hesitate and die off. There's no particular time it does it , it just has a mind of its own and does it when it wants. To be more specific , it'll run amazing then the car turns into a slug and no matter how you use the throttle , it doesn't make a difference. It literally just falls flat on its face . Complete loss of power . I've already replaced the afm, icv, throttle body, intake boot (and whatever sensors have to do with air/idle/etc) . I have no vaccum leaks. The valves have been adjusted , timing belt has been done and checked several times for accuracy ,compression is 100% consistent across the board.
I put the msd box in hoping it was an ignition issue. . which helped a lot of the issue, but the problem at hand (which I though was fixed ) is still present .. just presents itself in a not so severe form. This is literally my only major driveability issue , and it's frustrating being stuck with one major component that no one can seem to figure out.

Does anyone have any ideas on what this could be ? Or has anyone experienced something similar (if not the same ) issue ?
I'm open to any ideas. The only thing I haven't touched is the computer / control module . I'm not 100% on how the motronic works , but I've checked to make sure the computer was the right one for the car .

Anyone wanna help me save my alpine weiss/cardinal red e30 from a ls/ small block swap?

Thanks.

[jlevie]

Tee a gauge into the rail supply line and see what the pressure is during an event.

[NoM54me]

Save it from a small block? I think the M20 is a small block, of sorts. When you say it "dies off", does the engine completely shut off, or just continue hesitating? How does it idle when this happens? When does it go back to normal operation? Have you checked the fuel pump and main relays? If not fuel pressure related, perhaps you're losing spark. When this issue happens, remove the fuel pump fuse, and pull the coil wire from the distributor cap and hold it close to the intake manifold while someone cranks the engine over to check for spark. If you have no spark at the coil, the problem exists somewhere between the ignition switch and the coil. If you do have spark at the coil, put the wire back on the dist cap, and pull plug #1, repeat the test but with the spark plug held onto the manifold. No spark there means the problem is between coil and plugs. I had the same problem with my ES recently, twice. First time was faulty OBC relay. Bypassed it, fixed. Then it was an ignition rotor that somehow blew apart.

[purrfektrs]

Save it from a small block? I think the M20 is a small block, of sorts. When you say it "dies off", does the engine completely shut off, or just continue hesitating? How does it idle when this happens? When does it go back to normal operation? Have you checked the fuel pump and main relays? If not fuel pressure related, perhaps you're losing spark. When this issue happens, remove the fuel pump fuse, and pull the coil wire from the distributor cap and hold it close to the intake manifold while someone cranks the engine over to check for spark. If you have no spark at the coil, the problem exists somewhere between the ignition switch and the coil. If you do have spark at the coil, put the wire back on the dist cap, and pull plug #1, repeat the test but with the spark plug held onto the manifold. No spark there means the problem is between coil and plugs. I had the same problem with my ES recently, twice. First time was faulty OBC relay. Bypassed it, fixed. Then it was an ignition rotor that somehow blew apart.

Small block meaning gm motor. engine doesnt turn off.. just loss of power, then goes back to normal operation when it want. It could hesitate for two seconds, or thirty. Or anything less or more . Completely inconsistent with when it decides to act up. Fuel pressure is on point. No issues. Fuel pump is new , fuel filter is new, connections are where they should be. I have spark. Rotor is fine,cap is fine (they are both new ) . Ill try that test just for the hell of it since there isnt much else i can try.
Could a faulty computer cause any of the issue ?
Ive basically ruled out any fuel problem. I fixed the wiring/short i had but that had nnothing to do withthe driveability.

[jlevie]

If fuel pressure is okay, the next likely cause would be a loss of timing data. Which could be bad timing sensors, engine harness, or DME.