Help me figure out what part is failing.

[Keyan]

So I've always had this issue but it's been getting worse recently so I thought I would get our hive minds to take a look at it.

Important mods:
MAFT gen 1
Ls1 maf in oem location
Chrome ecu
Walbro 400
Hotwired pump
Fuellab fpr
Stock injectors


The problem is as follows.
When driving, at least once every drive cycle, I will be cruising down the road at normal AFRs, when suddenly the car will loose all power and my wideband will display full lean. Gas input barely does anything. After about almost a second of it, suddenly the car will slam back into power and AFRs will drop to like 11.5, then do the cycle again 2 or 3 more times. After the car's "event" it will clean right back up and I'll be cruising at normal AFRs again.

Also it has this issue, where right after I change gears and get back into the pedal (lightly) the car will exhibit a similar no-power where the AFRs will chill or hang around 17 before my car goes "Oh yeah it needs more fuel". This does not happen all the time, but is most noticeable going into 2nd and 3rd.

The vehicle also makes no power until about 3000 rpm at which point a switch will feel like it got flipped and my car will lurch forward with power. Dropping below 3 grand and accelerating replicates the issue consistently.


What I've done to attempt to figure this out:

It originally started when I had it with a 3.5" blow through maf. I converted back to stock draw through with a 3.75 maf. No change.
I tried cranking the fuel up on the MAFT. No change.
I tried swapping my evo injectors for my stock ones (that are known to be good). No change.
I tried swapping out an old used Walbro 255 for a new Walbro 400. No change.

I tried turning off short term fuel trims and long term fuel trims in Chrome - - that made a change. Both issues completely disappeared. The car will run leaner than stoich at warmed up idle and cruise, but if I run through the process to replicate the lean-no-power, it's completely gone and instead AFRs react as they should for a problem-free car.

I can't figure out how to determine if the issue is my chrome ecu, my MAFT, or my air fuel sensors.

Not sure what my next step in diagnosis would be.

[OhioSpyderman]

Put your original ECU back in?

Sounds like bad Chrome thing....

I know nothing about Chrome....

Bob.

[Keyan]

unfortunately I sold my rare '93 ecu a long while ago


i am considering whoring myself out to swap in a OEM MAF sensor to atleast cross that off the list of potential issues but even that is difficult without paying money for something that will just sit in my tool box after i swap it in for 30 seconds.

[Ange]

maybe it's the same issue I had. fuel pump o-ring. but if you changed pump you should have noticed the o-ring. but maybe not.

bad one can have this effect in the tank

[OhioSpyderman]

What part number ECU are you wanting?

Bob.

[DocWalt]

That's a VERY popular failure point on old VWs like I drive, so I'd certainly look into that.

[Keyan]

its not the pump, i changed it from the o-ring system to e85 compatible fuel hose when i was in there.

it happens too rarely to be fuel pressure. plus when i disable air fuel trim feedback, the problem goes away.

[Keyan]

What part number ECU are you wanting?

Bob.

i forget what the part # is for a 93.

[Jimvr4]

Closed loop fuel trims are not working. When you hit 3000 you are open loop and power returns. You either have a wiring issue or bad narrowband (s)

[Keyan]

What part number ECU are you wanting?

Bob.

0663 is the number I am looking for.