3.0 o2 sensor disconnect?

[mack6820]

Hey guys. I was at the racetrack this weekend and had the opportunity to ride in the same year and same engine, 1983 3.0 with a more experienced driver. I couldnt believe the difference in power between her car and mine. I talked with her mechanic and he said to disconnect the oxygen sensor and also disconnect and plug the retard vacuum line on the distributor. Has anyone else done this?
Note: She was running headers with straight pipes and I know that would make a big difference in the stock set up I was running.

Im the red one on the left.

[mack6820]

anyone? Well I unplugged the 02 sensor and I think I feel a bit of difference. Not so sure yet but I do think I feel some fifference in the power. I need to find a dyno in the area and test this more.

[jason2guy]

unplug it then u need to have ur mixture set, around 3.5%
i run mine this way

[SP2]

John Walker recommended I do both, as well as set the CO to 3.5%. He puts a metal screw in the vacuum hose to block it off.

[psalt]

On CIS lambda there is a throttle switch that disregardes the O2 sensor after 35% throttle, so whether it is connected or disconnected, it is irrelevent to WOT performance. The O2 sensor is good for part throttle cruise and mpg. The vacuum retard is an HC idle emissions device, most cars run cooler at idle and cold start better with it disconnected. It has little or no effect on WOT performance, there is not enough vacuum in the manifold to trigger the retard mechanism.

You are probably feeling the added throttle response and a few extra hp from the exhaust change.

Paul

[don gilbert]

mack, as paul said, the 02 has NO effect on wot performance, once past the 35degree throttle switch, 02 system goes into a open loop (it not working) leaving it pluged in will increase your fuel milage and make your enginge last longer, also, the advantage of an 02 cis car, (80-83) is the ability to make afr adjustments past the 35 degree swith (richen it up) and still have excellent drivabilty and fuel milage when just cruising or idling. You need to put a dwell meter on it to make sure its working, as almost 90 percent that i have worked on are not working anymore,(relay or bad sensor mainly) as for the retard line, leave it unplugged and reset you idle and timing, its an emmision device that make the car run hot at idle (these 02 cars were made to run as hot and lean as safely possible) there is alot more power to be had in you 02 car, you just have to unlock it with a few mod, exhaust, timing and fuel mix (adjustable wur).

[don gilbert]

Ive seen alot of cars that have had the 02 disabled by pulling the relay, DO NOT do this, the fuel enrichment is at wot is provided by your frequency valve relieving control press, which richen the mix, pulling the relay will create a very lean situation at wot, which is not good

[mack6820]

Thanks for the advice. I think I need to find a good CIS mechanic in the Oklahoma City area and just have him go through the whole car. So far havent been able to find one.

[don gilbert]

you dont need a cis tech, its a very simple system, get the bently and ben watsons "how to tune and modify cis" and study it, buy a few simple tools (cis press. gauge, timing lite, dwell meter) you can be a cis master in no time,

[PorscheGuy79]

I have my SC engine with a pulled O2 (as it was when I bought it) and a disconnected vacuum retard on my dizzy. Thanks to some help from Souk we were able to tune it in without these items and there was defiantly a little more kick to it.

Then again Souk doesn't need a sniffer, just his nose, that guy's a CIS god. Last time my car went for emissions, I was admittedly nervous, but it came out a Low Emissions Vehicle for that year. Take that Prius!

[dvkk]

Originally Posted by don gilbert

....) as for the retard line, leave it unplugged and reset you idle and timing, its an emmision device that make the car run hot at idle (these 02 cars were made to run as hot and lean as safely possible).....

The idle retard's function isn't to make the engine run hotter, it's to have retarded timing so your HC emissions are really low. Yes, your engine temps will go up when the idle timing is retarded, but how long are you letting your car idle? More than the cycle of a traffic light, turn it off. Leave it plugged in and don't excessively idle your car, your car isn't going to melt down. That's a myth.

[don gilbert]

like i said, unplug it, it makes your car run hot, and does nothing for performance, it was a early and stupid way to help control emissions

[Akira28]

Just for clarifacation do you plug (with screws for instance) both the vacume line and the inlet on the distributer?

Just making sure for us newbie troubleshooters..

Akira28

____________
1983 911SC Targa
1984 944 NA

"When it started it blew out smoke, and it smells like burning oil, is that bad?"
"That depends, Are you talking about the barbque or the car?"
"The car"
"Then That's fine babe"

[Gogar]

Originally Posted by Akira28

Just for clarifacation do you plug (with screws for instance) both the vacume line and the inlet on the distributer?

Just remove the line from the distributor and that's done. Then, plug the vacuum line with a screw and a hose clamp, or a golf tee, or whatever.

the BEST way is to follow the line up to the airbox and remove it completely, and then plug the nipple on the airbox with an appropriate sized "vacuum plug". That way the line isn't flopping around the engine bay.

If you'd like to plug the nipple on the distributor with a vacuum plug as well that's fine, but it doesn't change anything performance-wise. Just keeps it clean.

[mack6820]

I didnt really notice any difference in power. But when I disconnect the O2 sensor, the car does run rich and you can smell it.

[stlrj]

Originally Posted by mack6820

I didn't really notice any difference in power. But when I disconnect the O2 sensor, the car does run rich and you can smell it.

Careful. Running rich could potentially burn out your cat. if it's still hooked up.

[Gogar]

Originally Posted by mack6820

I didnt really notice any difference in power. But when I disconnect the O2 sensor, the car does run rich and you can smell it.

+1 disconnecting your o2 sensor and changing the idle mixture isn't going to find you gobs of horsepower. If you could do two things (IMO) instead I'd make sure your control pressures are right, and make sure you're throttle linkage setup is getting WOT. Oh, and check your timing. Oh, and make sure your distributor's mechanical advance is up to snuff. Oh, and make sure your Johnson rod is torqued to spec.

[Won]

Originally Posted by Akira28

Just for clarifacation do you plug (with screws for instance) both the vacume line and the inlet on the distributer?

Just making sure for us newbie troubleshooters..

Akira28

You want to remove only the retard line. The other one is vacuum advance which also has no effect on WOT but does help improve fuel economy on cruise. You will want to keep this function. The one that causes an increase in idle when disconnected is the retard.

I may have mentioned this in other CIS threads before, but I really didn't like the way the car drove with the vacuum retard line disconnected and plugged. WITH the retard connected, the slightest crack of the throttle plate would remove the vacuum signal and RPM would jump straight up to 1600 RPM or thereabouts. To me this gave a sense of better throttle response, because you get this instant timing advance per se so the first 5% of throttle travel actually translates to more increase in RPM compared to the rest of its travel. Once the retard is gone, one must bring the idle back down to ~1k RPM using the idle bypass screw. Now the instant 600 RPM jump is gone, and it just didn't suit my driving style. I did not notice any change in oil temperature in stop and go traffic with or without vacuum retard. Also, without the retard the engine had a higher tendency to stall so it became difficult to get the car moving just by clutch actuation without additional throttle input.

[stlrj]

Too bad they call it retard because everyone looking at it would prefer not having anything with the word retard on their car, even if they do not understand that there really is nothing wrong with it since it does increase throttle response and performance.

Disconnecting the retard feature is a good way to loose performance.

[don gilbert]

Disconnecting the retard feature is a good way to loose performance??? adjusting your timing and idle will make your car just as snappy as before