what is this?

[KarenL2888]

It was unplugged....causing the check engine light. But it ran great. Now the oil change guy plugged it in....and she stalls when at red lights.

[KarenL2888]

[GP1138]

A vacuum junction block?? Those are various and sundry vacuum lines..

 

Also, moving this to Powertrain as this is not CSC specific...

[RobertISaar]

yeah, that's the main vacuum point for a LH0... engine should run horribly with it unplugged, it's a huge vacuum leak. after a few(usually failed) starts, the ECM quits looking at the MAP sensor signal and goes into a weird fueling mode that pretty much throws gas in, hoping that the O2 sensor can correct for it.

 

if it's stalling now with it plugged in, i'd considering doing an ECM reset to have it relearn the necessary IAC values, since it is probably still used to the gigantic vacuum leak that was there before. it will be commanding an abnormally low amount of airflow, causing a stall. if it still runs bad after an IAC relearn, i'd look at the MAP sensor or it's hardline as being bad. possibly the CCP solenoid stuck wide open too.

[KarenL2888]

My mechanic says the computer in 1991 could not "learn". He says likely when they replaced the engine, they bypassed this vacuum point to get it running. He says since its emission exempt it probably doesnt matter that its bypassed.

[RobertISaar]

the thing is, it's not an emissions item.... it's the basis for all fueling and spark control.

 

the ECM certainly learns(and retains) a lot of values.... the 1227727 ECM traces it's roots to the 1227730, which was originally used in 1987 model year cars, and those most certainly "learn" values as well. the 7727 came out for the 88 model year in W-bodies.

[intern8tion9l]

How the hell did it run at all with that unplugged? It's quite important

[White93z34]

If you live in Pittsburgh and put more then 3000 miles on it a year and have standard plates its not emission exempt.

 

And yes, its rather important. Drive the car some the stalling should work itself out. I'm rather impressed it ran worth a damn at all with that unplugged.

[KarenL2888]

It has a classic plate so emissions is not an issue. Thanks for all the help guys! I appreciate it!

[Go4DaMo]

Those'll pop out if you don't crank the engine long enough to start it. Have seen them ziptied on before.

[GnatGoSplat]

I've seen some 3.1Ls have a plastic cover over them to keep them plugged in. Idle relearn as Saar mentioned is probably what it needs to run right. IAC could also be sticking, I've had that happen before and was able to fix a sticking IAC by cleaning the threads and lubing with motor oil. Unplugging it was probably somebody's idea of a fudge-fix.

[intern8tion9l]

That clip is one of the rarest w body parts in existence

[GnatGoSplat]

That clip is one of the rarest w body parts in existence

 

Ah, nevermind. Only TGPs got the clip. GM # 12397881.

[intern8tion9l]

I never realized that! No wonder it's so rare

[Night Fury]

Yeah you need that. Mine popped off a couple weeks ago and it ran so bad it nearly left me stranded. Popped hood, slipped those bad boys back in, Voila!

 

I'm sure it just needs a relearn. If you just keep driving it, it should 'learn' that way also and stop stalling after a few days. As others have said

[MonzaRacer]

That sends vacuum to all sorts of things including some versions fuel pressure regulator, accessories, EGR, pcv.

Try disconnecting negative from battery for few minutes then restart and drive for bit so it can relearn.

Basically it was a huge vacuum leak and defaulted some other stuff thats vacuum operated