jdhh74

iTrader: (2)

Hi all,

I'm hoping someone may have insight into this. I have a 1984 L69 Trans Am with California Emissions. It has the MAP sensor on the driver's side of the firewall but lacks the Barometric sensor that is usually found on the passenger's side. The pigtail to connect a bar sensor is there - but tucked up behind the engine.

Does anyone know why the CA cars didn't have this? Would there be any benefit to adding one now? The car runs fine without it and has never thrown any check engine codes so I'm assuming that it's not missed. Would the ECM be programmed to look for/use it if I added one or did CA cars have unique programming as well?

If any has the inside scoop, I'd love to know!

Thanks,

John

sofakingdom

iTrader: (1)

AFAIK, they did.

Look at your vacuum line diagram.

When I lived in So Cal (Carlsbad) and would frequent the Ecology Auto Parts over on the 78 in Oceanside, seems like ALL the CA cars had it.

If the ECM is looking for it, then yes, it's beneficial to have it. Can't tell you for sure if you just hook one up and the ECM recognizes it. What it does is, remember that "vacuum" is an absolutely PERFECT indicator of engine load (i.e. the combination of what the engine is putting out, against what the operator is demanding); but "vacuum" is the difference between ambient air pressure, and manifold absolute pressure. (aka MAP) For REALLY PRECISE measurement of engine load, gotta have BOTH the MAP and the baro #s, because "vacuum" is a function of BOTH.

Jaime-TA-84

iTrader: (1)

Noticed this in my car a while back.

RamIt

My 84 California L69 also did not have one installed but had the pigtail in the harness. I put one in but it seemed to have no difference in running. I am not the original owner so who knows what happened over it's life

badlefthand

One owner 1984 firebird made in Cal, has a boro senser pass side up high on firewall. Suposed to send to Ecm a signal as absolute pressure rises or drops and compares pressure with manifold pressure ( vacume senser on drivers side) I dont think there is any effect on how car runs unless maybe in Rockies. 3 sensers on curicut, tps. vacume senser and boro senser. Im on my last effort to find which one is shorting out tps if not ECM. No vacume line to boro senser.

jdhh74

iTrader: (2)

Hmmm... it seems like, as with a bunch of things about older GM cars, there's no clear answer. Some have it and some don't. I'm the 2nd owner of my car, the previous owner kept the car stock and had all work documented. I don't see why anyone would have pulled the bar for no reason - and, since the ECM isn't looking for it, it would seem to be by design.

I also tried attaching one to the pigtail for it and it made no difference. So it seems there are CA cars that never had it by design.

I wonder if it was a running change of some kind since some CA cars, it seems, did come with it stock.

I guess I'm really just curious why this would be. I know the CA cars had to have a CA certified CAT, that makes sense. But what benefit would there be to emissions to remove the bar sensor? I wish there was some documentation on this somewhere. I have the 84 GM manuals and they don't mention anything about it.