Disconnect my oxygen sesnor????

Rukus

Rukus

Member
#1
Messages
328
Likes
0
Location
Medicine Hat, Alberta, Canada
#1
I was told that if i time my car to TDC on the #1 pistion and mathc up the timing marks on the rotor to the distributor housing, and deadset my idle valve, (which i have done) i can disconnect my oxygen sensor and run non lambda. i have the l-jetronic Fuel injection system.. not the motronic.

Does this sound plausible to people?

I know since i disconnected the oxygen sensor my car runs A WHOLE lot smoother, and idles smoother.

I am thinking i just should get a new oxygen sensor.. becasue i think my fuel mileage also went down a whole lot... but the power response on my car is awesome!
 
E

epj3

Senior Member
#2
Messages
7,370
Likes
0
Location
Lancaster, PA
#2
Well, first it might be running a bad fuel/air mixture, where it will possibly overheat the engine and cause catalytic melt down/failure. You should DEFINITELY replace the oxygen sensor, the sensor was probably bad to begin with so it was telling the engine to use less fuel -- so it would hinder performance. Now, it'll run without the sensor giving errors, but you'll have other problems now, even carbon buildup.

Definitely replace it, you'll get better mileage and I doubt you'll loose any performance.
 
B

Ben

Active Member
#7
Messages
576
Likes
0
Location
NY
#7
yeah they dont have emissions testing or inspection here. i thought about taking the cat out on my porsche, but then if i move anywhere else where they do have emissions, ill have to put it back in.
 
Rukus

Rukus

Member
#12
Messages
328
Likes
0
Location
Medicine Hat, Alberta, Canada
#12
You cna get REAL decent mufflers off ebay for like $30 - $50usd , and replace the piping at any shop for about $175cnd.

(sorry for the currency crossovers lol)

one thing i ahve learnt about performance is that, brand names don't make you go faster. Its what you use and how you do it.
 
B

bichmgnt

Member
#13
Messages
368
Likes
0
Location
Ventura CA
#13
Running the engine with the timing at TDC is probably not the best way to go. With the spark firing at TDC the fuel takes time to ignite and is reaching its greatest volume while the piston is going down already. When the engine speeds up it only gets worse. That is why the old mechanical distributors had weights inside that mechanically advanced the timing the faster the engine ran. Typically the older engines would idle with the engine firing at a couple degrees BTDC and would advance to ~35 degrees or more at high RPM. I don't know what the computer does to the timing without these references. It probably does the advance since it seems to be running well but there are still other issues.

Disconnecting the oxygen sensor makes the car run very rich all the time. That is why your mileage has suffered. Properly running, the oxygen sensor maintains the air/fuel mixture at 14.7:1. Replacing the oxygen sensor will probably fix the original problem, or at least let you verify that it is not the original problem which you should probably fix.

If there was a significant gain to be had in disconnecting the O2 sensor it would be all over this board. Everyone who didn't live where their cars got tested would be advocating it. I just don't see how it could be better, only disadvantages. besides poorer mileage, running that rich will require more frequent oil changes because more gas is getting into the oil. I'd expect your plugs will foul up quicker too. Carbon buildup was mentioned but I don't know. It wouldn't surprise me, though.

Steve
 
L

ldzpstnr

Member
#14
Messages
174
Likes
0
Location
Oregon
#14
Ok.

The 1984 and 1985 318i's L-Jetronic fuel injection system doesn not control the ignition timing. All it does it keep the fuel mixture correct. Disconnecting a good working O2 sensor will make the car run richer, but only a little. The O2 sensors on these cars just fine tunes the mixture. The AFM really adjusts the fuel mixture.

I ran the wheels off of TWO 318i's, still have the cars also. My '85 318i had a header, no cat, 2.5 inch exhaust back to a hooker Aero chamber muffler for a long time. It was very loud, but also would scream above 4,000 rpm. I had bigger injectors, and a K&N factory replacement filter. My 318i would move, especially with the 3.91 differential.

I never did it but I think you can do a m30 AFM conversion on these cars just like you can with the 325's. I think the 318 and 325 use the same or very close to the same AFM. I know the used the same fuel pressure regulator and I think the injectors too.

At near the end of its life I pulled off the fuel injection and put a Weber 32/26 on a intake manifold off an older 2002 bmw. My fuel injection had a wierd cutting out problem that I could not trace, it was intermitant and electrical. I now suspect it was the AFM. But wow that 1.8 liter screamed with that weber and that header.

You can run your timing pretty hot, advanced. Just keep advancing it until it pings a little at engine speeds less then 2,000 rpm. I never ran the motor less then this, its better to rev then lug. A slight ping will not harm an engine, only a ping at mid to high rpm will. My car got up to 35 miles to the gallon, with an average of 32 city and highway combined. Just my recommendation of course, its what I did.

Later.
 
L

ldzpstnr

Member
#17
Messages
174
Likes
0
Location
Oregon
#17
Hey now,

If the 325's were the best, BMW would have used one to win the World Touring Car Championship in 1987, not a S14 2.3 liter four cylinder m3 :). And all BMW did to make the m20 six cylinder was (basically)add two more cylinders to the M10 four cylinder. But I live my '87 325 with the 2.7 eta. :)

www.bmwworld.com has a lot of old bmw engine info and history. Later guys and gals!

Aaron
 
You must log in or register to reply here.


Top