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For the last 3 weeks I've been battling a cluster eff of symptoms most here would think are related to failing sensors, injection or other. And there were no CEL or codes stored(!!!) Things replaced or checked in order Replaced efi fuel pump & filter. Pump had died in mid July. Blew air thru suction line to clear any junk on fuel tank strainer - nothing Checked evap cannister & fuel tank purge lines - good. Checked evap sol valve - good. Replaced plugs, cap & rotor, spark plug wires, coil. Replaced optical sensor in distrib & upper 6200 sealed ball brg. Needed optical sensor as there was corrosion inside distrib. Brg was 'crunchy' Replaced MAF sensor - twice. Once with unknown used one & once with "reman" Cardone MAF. Waiting for known good genuine Hitachi MAF to arrive. Then will put "Car-do-nay" on shelf as spare Checked CTS - good. Pulled apart air cleaner & snorkel under fender to check for obstruction - good Rebuilt SPFI throttle body & checked TPS for dead spots - good Checked front cat, rear cat & muffler for obstructions. Replaced rear cat for general principle as it was a 8 yr old aftermarket Magnaflow CA legal cat. Added an O2 sensor bung ahead of new cat for 96 EJ efi conversion. My 87 4wd GL was bucking-cutting out randomly. Stalling after starting. Losing power at top end in any gear. Got to point of being undriveable. I have no room in driveway right now(of course) to Ej it otherwise I would have. Will have to wait until I have space to work. Car is registered in MT so it is exempt. Yay! After replacing the rear cat & getting no where I stopped for the night to test drive again in morning. Glad I did. Started with difficulty. stalling a few times until it ran with coaxing from me using throttle pedal - a lot of coaxing. As I was getting in driver's seat, I hit the lower dash panel. Then it died. AHA!!!!! Pulled down panels. Started digging into the wiring to look for loose connections but found none. Pulled down ECM & swapped in my backup ECM. Replaced ignition & fuel pump relays above ECM mount while I was there(had ordered them a week before just in case). Started engine with no problem & no stalling. IAC behaved normally raising idle to warm up. As I was lifting ECM back in place the engine died again. Hmmm. Started checking further into wiring. Found that there was corrosion in sensor connector - the translucent white connector with all the shielded sensor wiring. All sensor wires go thru there. Cleaned the contacts.Then repeatedly put conn together & pulled it apart a few times to 'wipe away' the corrosion. Put ECM back in mount bracket. Went for test drive. Runs better than it has in months. I can recall some hesitation, loss of power & etc when I came back from MT. This must've been it all along. Anyone else mystified by a long long list of things checked or replaced with no positive result ought to look under the dash at sensor connector(its next to rectangular gray diode to left of ECM) & ECM connector corrosion. Look to the engine bay harness for corrosion too. Any intermittent connection in harness would replicate the symptoms we associate with clogged cats, failing ignition, failing injector, failing MAF, etc. Enough to drive you nuts............. Happy hunting!