Ashton89iroc

Alrighty guys, I got a weird one for you. I've done about 3 days of searching and haven't come up with anything for my individual problem. For staters I have an '87 that originally had a 305 TPI, I pulled the 305 and dropped in a brand new Vortec 350 crate. I made sure to swap all the proper parts for a 350 swap. The brand new parts (relevant to the problem) list is as follows

NEW:
pick up coil
ignition module
cap & rotor
plug wires
spark plugs
temp switch
fuel pump & filter
IAC sensor
throttle body gasket set
O2 sensor
oil pressure sensor
Sent my '89 ECM to TunedPerformance to get VATs eliminated.
Injectors sent to TPIS to get flow tested and checked.
….pretty sure thats it.

Ok, here's the issue. I could NOT get it to run for a few days. It would crank and fire up instantly then literally would die immediately after, consecutively. The thing absolutely refused to Idle unless I kept feathering the throttle. Now, I after smashing my head on a wall for two days, I got smart and unplugged the TPS and MAF and it fired right up and idled like hell, but idled none the less at 2500 RPM flat. I plugged the TPS in and left the MAF unplugged and it threw code 22, so i replaced the TPS. Now, with ONLY the TPS plugged in it fires up and jumps up to 3500 RPMs then slowly goes down to about 1000 or so and bounces between 1100 and 900 and throws code 33. If i plug the MAF in and set it aside NOT mounted on the throttle body, it idles flat at 1200 RPMs but throws code 34. If i mount the MAF on the throttle body while plugged in, it's back to square one, it fires up then dies IMMEDIATELY with no codes at all.

So depending on if the MAF is plugged in or not I'm getting either code 33 or 34. Funny thing is, I have 3 MAFs. One of them doesn't work either way, so its junk. the other two (which came off perfectly working engines) work only when plugged in and set aside, but will kill the engine if mounted on the throttle body. You're all probably thinking its just a bad MAF, but if it was bad it should still fire up and at least idle somewhat when on the throttle body, yea? Even if the burn off or power relays were bad it shouldn't die IMMEDIATELY after firing….right? I find it hard to believe that all three of my MAFs are bad.

Basically, everything seems to work fine EXCEPT when the MAF is on the throttle body. when the MAF is plugged in but set aside I get code 34 and when its not plugged in at all I get code 33.

Do I just need a new MAF? I REALLY don't want to drop $130 dollars on one….

Ashton89iroc

UPDATE:

I was able to get it running for a bit with the MAF on the throttle body like it's supposed to. It idled fantastic for a little bit then the engine popped a little and ran like hell. I noticed I didn't have a MAT sensor plugged in and can't seem to find where one should even be.

lakeport

MAF probs suck, working through one myself, with help from here of course

the MAT is under the plenum

lakeport

MAF probs suck, working through one myself, with help from here of course

the MAT is under the plenum

and if you do go with a new MAF stay away from the japo junk, go with the AC Delco

Ashton89iroc

turns out I had a MAT sensor issue, my MAF wasn't bad at all. MAT sensor was mounted in the head for some reason, i had it moved up to the bottom of the plenum and it ran like a dream. stupid how little things like that make huge differences