[Dave A.]

You mentioned that you could smell this odor before you replaced the exhaust system, and also after your new exhaust system was installed. Does the odor smell like raw gasoline from a possible fuel leak?

 

[Dave A.]

How does your car run? Good, fair, poor? You mentioned that the inside of the tailpipe is black. That's a good indication that something is causing your fuel mixture to be on the rich side. How long has it been since you did a complete tune-up on the engine and cleaned the fuel injectors? An engine that is in poor tune can cause exhaust odor to increase since some amount of raw fuel can be mixed with burn't fuel, especially if the injectors aren't operating up to par.
How about the gasoline in Australia. Have any recent changes been made to the gasoline formulation in Aus. such as the addition of Methanol??
What year is your MKII? Is your check engine light coming On? I also have a suspicion that you may have a bad 02 (oxygen) sensor that may be causing your air/fuel mixture to be running a bit rich most of, if not all of the time.

 

[Dave A.]

You can check the output (feedback) signal of your 02 sensor by connecting a voltmeter to the 4-terminal service connector located behind the AFM on the passengers side strut tower. Terminals VF and E1. Page FI-59 in the 83 TSRM. My guess is that you may indeed have a bad 02 sensor. That would explain the rough idle and smell of a rich mixture. The ECU can detect when the 02 sensor is outputting a lean signal for a longer than normal time period and cause a code 21 to be stored and turn On the check engine light. OTOH, the ECU doesn't detect when the 02 sensor outputs a rich signal for a longer than normal time period, thus no check engine light even though the sensor is not operating properly.

 

[Dave A.]

I really don't know which MKII's have an 02 sensor and which ones don't. The fact that your car doesn't have a catalytic converter from the factory could also mean that it doesn't have an 02 sensor. Dirty or clogged injectors would cause more of a lean condition in your case if your car indeed does not have an 02 sensor. The feedback signal fom the 02 sensor would normally tell the ECU to widen the injector pulse and richen up the fuel mixture if one or more injectors are badly clogged, but that won't happen if the EFI system doesn't have an 02 sensor. You might try checking your fuel pressure regulator and see if it is working properly. A ruptured diaphragm in the FPR could allow extra fuel to be drawn into the intake manifold through the vacuum hose connection. Try disconnecting and plugging the vacuum hose on the FPR and see if that makes a difference while you're driving. The rough idle may also improve some with the hose disconnected but the idle mixture will be a little rich with the FPR valve closed.

 

[Dave A.]

The fuel pressure regulator is located on the fuel rail near the firewall on the drivers side. Try disconnecting and plugging the vacuum hose and go for a spin and see what happens.

 

[Dave A.]

Ooops! I forgot that you have RHD in Aus.. FPR would be on the passengers side, not the drivers side.

 

[Dave A.]

If the injectors are leaking down then the mixture should get more rich at idle when you disconnect the vacuum hose on the FPR.

 

[Dave A.]

The fuel rail is located below the throttle body and is secured to the intake manifold runner assembly. The FPR is mounted on the fuel rail at the very back of the rail, round cylinder shaped device about 2-3 inches long and has a vacuum hose connected to the top of it. Try disconnecting that hose while the engine is idling and see if perhaps a small amount of fuel comes out of the top of the FPR while the engine is idling. If you see fuel, the diaphragm in the FPR is shot. Page FI-50 in the 83 TSRM. Also, if the FPR leaks when you disconnect the hose, shut everything down to avoid creating a fire!!

 

[Dave A.]

That is weird! Are you sure there isn't a hose right on top of the FPR? Maybe you're confusing the FPR with the pulsation damper that is round and has a plastic cap on top?

 

[Dave A.]

Page 4-21 in the Haynes manual. Illustration 19.9a shows the FPR located in the center of the fuel rail on a bracket. I forgot that you have the 5M-E and not the 5MGE. My bad! 8)

 

[Dave A.]

Ahh yes, that nasty rotten egg smell of Sulfur! YUCK! Diesel fuel is bad enough in that department. I'm still wondering what's causing your gas mileage to suffer. The higher Sulfur content shouldn't affect your gas mileage much, if any. The fuel pressure should be 33-38 psi at idle with the vacuum hose disconnected on the FPR and 27-31 psi with the vacuum hose connected at idle. Hmmmm, I'm still leaning towards a fuel pressure problem, either from a ruptured diaphragm in the FPR or perhaps a leaky CSI that's richening up the mixture throughout the RPM range.

 

[Dave A.]

The Sulfur smell will be worse in your case since you don't have a converter. The rich fuel mixture will just make the smell worse as well. Hope you can find the cause soon! Those fumes are very unhealthy!

 

[Dave A.]

He lives in Aus., thus no cat. or 02 sensor to cause the problem.

 

[Dave A.]

Hmmm, the 02 sensor is considered an emission control device so it would seem a little strange that he would have an EGR valve but no 02 sensor. The Haynes manual indicates an 02 sensor on the MKI on pages 1-42 and 6-14. According to the Haynes manual, the ECU on the MKI doesn't have a self-diagnostic feature and the 02 sensor is supposed to be replaced at the "recommended intervals". Hmmmmmm!

 

[Dave A.]

Take a closer look! Maybe your car has an 02 sensor after all.

 

[Dave A.]

Ahh...that explains it!! Great info.!