sorting the m45 on my 91
 

hey cats. i need a little help with this one. sorry for being long winded - some back story for the bigger picture. so I picked up a gen 1 JR M45 kit a few years ago on the cheap, installed it, the fpr and bipes timing box it came with and drove the crap out of it. it would bog down, lose power around 3.5-4K rpms then it would kick in all the way to RL. not awesome but fun-er. i had the intention of upping the boost but with CARB (being lame) and learning here that the $ needed to eek out a few more psi was dumb, so i didn't. figured i'd go turbo if i could find a CARB friendly setup that wasn't stupid cash but never did. then recently i stumbled across a newer m45 kit that had just been rebuilt, new coating, new bearings, smaller pulley (68mm) off a wrecked NB - for 1/3 what i'd sell it for - so i picked it up. i installed a wideband, boost gauge and TD fuel card - remember CARB - fired it up and idle was completely jacked, over 2200rpm and surging up and down - and the CEL came on. Code 34. I didn't drive it at this point.

I couldn't budge the idle screw so i pulled the SC off and had it on the bench next to the old one when i realized it has an NB TB on it. I thought this could be part of my issue but couldn't swap the TBs cause the 1.6 one won't bolt up to the new blower. I sorted the idle screw (it was all the way in after all) and got it installed again. The throttle cable felt a little tight so i loosened it up a bit too. It was a little better, car now idles at 1900, surging up to 2K and back but still throws the same 34 code after being cleared. when i test drive it has no power down low, bogs down significantly with anything but very slow increase in throttle, until it gets up to 4K or so then runs better close to like it should (open loop).

the idle rpms change when turning on/off the AC and idle stabilizes a bit when the car warms up (albeit stupid high).
no change in idle with TEN/GRD jumped.
afrs swinging back and forth between 13.5 and 15.5 at idle.
car has 20lbs of vacuum at idle
i've seen it get up to 7psi boost on the one or two runs up the street i've done.
afrs under load range from 10-16, from what i could see

anybody got an idea of a process to work thru this?

Oh, also, I did swap the TPS over from my original 1.6 TB to the NB TB so I could use the same TPS extension cable. Is alignment of these critical? It's only "sensing" WOT and closed, right?

Any ideas are much appreciated.

How is your idle air control plumbed?

^ correct question. It needs to be drawing air from before the throttle body if you're using stock ECU.

bone stock, haven't touched it. good stuff - I'll more closely

iac is on the dummy tb, so downstream of the nb tb on the back of the blower.
filter -> maf -> tb -> blower > dummy tb / iac -> man
this is how all these sc kits are setup and just a different blower with an NB TB on it for me.

i'm going to tweak the card to add more fuel in the mid rpms and take a couple runs to see if i can address the hesitation as it comes out of closed loop now while i got some light left but i have to get a grip on this idle issue.

i'll rig up a feed line from the other side to test drawing air from before the throttle body tomorrow. i can't believe i went this long with FI w/o being able to see afrs in real time. not overrated.

i didn't have to rig anything. the iac was plumbed as recommended - hose from the elbow behind the sc around the front to the iac with a check valve (cv works and is in the proper direction). i swapped the other SC back in, the one with the NA TB and boom 900rpm idle and the 34 is gone. soon there will be 2 M45 kits on the classified, both work - albeit with bandaids and sacrificing many many meows, but i'm done. mods please delete.

We don't delete threads here. This is a searchable record.

Just to confirm what I've already done... that check valve is supposed to be setup to allow flow in the direction of the dummy throttle body correct (so away from the supercharger only)?

Yes, the check valve should allow air in from a tap after the MAF/AFM, before the SC - flowing towards the dummy throttle body on the inlet manifold for idle stability, it should stop air from escaping from the dummy throttle body back to the intake under boost.