: O2 Sensor Questions

01-07-08, 01:00 AM
The Caddy is running a little rich. I'm smelling gas fumes through the exhaust. I've cleaned the EGR. It seems to have a misfire in it also. I'm not getting any codes back either. My guess in this situation is O2 sensors. The best way I've seen to get to them is put it on a lift which will not be a problem being that I have access to one.

These are my questions. How many O2 sensors do I have besides the two in the exhaust manifolds, and what are the proper names for those? So, many people are telling me different things, but from my understanding OBD-I only the two in the exhaust manifold.

I have a 94 Cadillac SLS. Will post pics of me installing once I get the info I need. :bouncy::bouncy: Also, will use nothing but AC-Delco, because I've had some bad experiences with Bosch.

01-07-08, 01:56 AM
Pull the trouble codes and tell us what you find.

01-07-08, 02:08 AM
Pull the trouble codes and tell us what you find.

Funny thing is...there's no trouble codes except my usual suspension codes.

01-07-08, 06:55 AM
It would be very hard for an O2 sensor to cause a fuel smell.

#1 if the PCM detects a problem with the O2 sensor it will stay in Open Loop. In open loop the car is running with out the use of the O2 Sensor. It is on a preset program.

#2 If a car is rich you would have LESS unburned gas out the tail pipe than if it was lean. Yes if the car is running lean you get more unburned fuel out the tail pipe.

#3 You have you car listed as a 94. The injectors, fuel lines, and the FPR are inside the intake. If you have a fuel leak inside the intake manifold and a Misfire you will get raw fuel out the tail pipe. This leak would include a stuck open Fuel injector. These will equal a WHITE FOG out the tail pipes

#4 You have a 94. This will not display Misfire counts and set Misfire codes. If you have a Misfire you can get a fuel odor. Lean misfire vs running rich:histeric: DO YOU HAVE A MISFIRE?

BTW I am not sure if the FPR is inside of the intake, but I think it is. I have only worked on a hand full of 93 and 94 cars.:hmm:

01-07-08, 10:57 AM
Rich = black smoke, carboned plugs, black fuzzy tailpipe = unburned gas in the mixture.
Lean = blistered plugs, burned exhaust valves (extreme), and white/gray tailpipe = too little gas.

01-07-08, 11:42 AM
'93 & '94 Northstar DO have the FPR inside the manifold. Remove the top of the manifoild. Turn the key on to pressurize the fuel system, but DO NOT crank the engine. If you see any fuel leaking from the FPR nipple, it needs to be replaced. The FPR is mounted on the fuel rail. The nipple is where a vacuum line is attached on an externally mounted FPR ('95+).

01-07-08, 12:39 PM
alrighty then. I will definately check that FPR. I've always noticed it when I changed the map sensor. It is under the intake.

01-07-08, 02:32 PM
Question came up about HC and Rich vs lean.
This chart sucks. I will post another later. One from a IM 240 course

01-07-08, 02:33 PM
That chart is way off looking at again.

01-07-08, 03:28 PM
:sneaky: That's an air to fuel ratio chart, so it's correct. Less air-to-fuel is rich, more air-to-fuel is lean. Stoichiometric fuel ratio is about 14.7:1 air to fuel. Less air, < ,as in 12:1 is rich; more air, > , as in 17:1 is lean.

01-08-08, 05:09 PM
Seems that this maybe the problem. What exactly will I need? I know there's a special wrench for the fuel line. Right? Is there a thread that will direct me on how to install this thing?

01-08-08, 05:43 PM
No special tools. Just remove the intake cover on the '93/'94.

01-09-08, 03:06 AM
You don't need to pull the fuel line.

Don't forget to tighten the torx bolts on the manifold cover correctly. Do NOT crush the rubber spacers! The suggested torque spec is so low that it's hard to find a tool that will measure it. The best way is to simply tighten them as far as they can be tightened without crushing the spacers at all, then give about one turn after. It will put enough pressure to widen them by about 1.5mm in their narrowest dimension (from back to front, not width). Those things serve as a relief mechanism in case of backfire, as two piece intake design does not have an overpressure relief valve, as the 1995+ single piece unit does.

01-13-08, 08:16 PM
Pretty easy install. The bad news is I left my digital camera on the tractor at the house because I was documenting a few things. So, I do not have pics of the install. Thanks for the help though. I'm sure there will be other times I get a chance to document work.