1993 wrx missing on full boost
 

Evening all.

this may be a lengthy post so please try to bear with me!

my 1993 wrx seems to stutter/misfire when it hits peak boost.
it's mildly tuned to about 280bhp using standard intercooler, a plug in chip in the ecu, (so still the non mappable ecu!), forged bottom end, blitz nur spec r, wide throat downpipe, no cats, zero sports caik and resonator delete, and a bunch of other modifications that have no bearing on the issue.

when I had it checked out a few years ago by Simon jgm at Surrey rolling road he said it was safe as far as the afr goes.


since then I've had to replace the up pipe because it was cracked, the turbo too but this was a like for like swap, usual fuel and oil filters as they are consumables, clutch, and a bunch of suspension related bits.

Intercooler doesn't look in the best shape.. lots of bent fins etc, so I'm wondering if that could be the cause of the misfire... any thoughts?

Otherwise I can only think that the turbo isn't quite the same as the original, or the up pipe was always leaking, or it needs new plugs/coilpack.

completely open to advice as all things being equal , it looks like I need a new ecu or at least an esl daughter board a to sort things out at this point!!!

Intercooler shouldn't/wouldn't cause a misfire.

93 car has individual coil packs, pull and check them, replace the plugs whilst you're on. If the coil packs are goosed, they usually crack under the rubber boot, replace them with Newage ones. PFR7-B's for a decatted classic.

How old is the fuel pump?

As above, coil packs are first port of call... very very common to find cracks under the rubber boots and that'll cause the exact issue you're having

thanks gents.
fuel pump age is unknown, so i'm gonna guess old!
don't think it was ever replaced with a walbro or uprated version as in its current state, it is running on the limit of the fuelling. (unless that's just the fact that it has some off the shelf chip in it!)

Replace the fuel pump whilst you're on since you don't know how old it is. Also, even if it has had a replacement at some point, they don't last forever. Easy job, although you might also need to get a replacement tank gasket.

As said on a 93 id replace


coils for newage
fuel pump
plugs
intercooler for a straight one, newage onwards

I didn't think newage intercoolers fit version 1 or 2 inlet manifolds? I'm a bit out of touch though.

I once imported a 94 wrx. When accelerating it would cut out. Turns out that the ECU was not screwed down tight in the pasenger footwell.

They can be made to fit, Paul. Part of it involves a sizeable hammer though. :D

It's easier on a Ph 1.5 car though.