After installing a new cat back, for some reason my FC will not move or rev up. I can get it started and can get it to idle. The exhaust smells fuel rich. I removed the air pump and put on an electric fan. I am wondering if I am just not getting enough air? Any and all constructive response will be greatly appreciated.i have been reading around but could not find a thread with similar issues in the time that I have had to research. I need to get this vehicle running asap. Thank you in advance. I don't really know where to start here. I also replaced the fuel filter. Idk if that matters but I felt i should mention it

 

Ok, is it an S4 or an S5?
Let's start there.

The air pump doesn't have anything to do with how much air the engine is getting - it pumped air into the exhaust.

 

Did you block everything off properly?

Next silly question, and idk if it matters or not, did you put the cat on the right way?

 

Without the air pump the cat can not function correctly. The cat will start the glow because it needs the air to help burn excess fuel.

 

Many folks remove their Air Pumps, particularly if they put in a high flow cat or delete it altogether. I did - I have the RB mid pipe. Not sure if they're still running the stock cat or a high flow.

 

The cat back is going to have nothing to do with the issue, cat glowing or not.

When the air pump was removed, did you cap things off? You either have unmetered air coming in or a vacuum leak.

Why did you remove the air pump anyway?

 

Sounds like a huge vacuum leak to me.

 

Did you remove the ACV as well? I agree with the others that it sounds like a vacuum leak.

 

Doesnt the air pump run some of the throttle butterflies? Could they be in the wrong location?

New to FC guy here.

 

Negatory

 

Yeah, that's a no.
On a S5 (89-91) the air pump does power the 5th/6th auxiliary ports, which are downstream of the throttle body in the intake manifold.
The S4 (86-88) uses exhaust vacuum (bewilderingly referred to as "exhaust backpressure" around here) to operate the same ports.

 

The S4 actuators begin to open at 1.2 psi, and are fully open at 2.1 psi above atmospheric
Generally, vacuum implies pressure below atmospheric, so why do you question the backpressure nomenclature?

 

Apparently, I was wrong.
I assumed that since the S4 actuator pulls down it was vacuum actuated, opposite the pressure actuated S5 actuator, which pushes up.
Also, the only fittings I'm familiar with in exhaust pipes were for crankcase evac systems, which were shaped to draw air from the tube, not pressurize it. Does the S4 airpipe make a bend inside the exhaust to face the flow?

 

Ya, if you look inside a stock s4 cat you'll see a tube inside the inlet of the cat, which is what the air pipe hooks up to, so yes, it is pressure, not vacuum

 

@ OP, the discussion above indicates things change a bit across FC configurations. The year of the car, any other mods, and things like that would be of use.

 

Not only that the EU market got strange setups also, such as he shouldn't have a CAS, should still be a distributor

 

Still learning here. Like when I started with the 8. But, his data says Minnesota.

When I get mine running, then I can look at stuff.

 

Thanks for all the replies. Removed air pump due to broken bolt on the belt tension adjust.

 

I was also wondering if there were any memebers in southern Minnesota?

 

A vac leak should cause it to run lean, not rich (more air getting into the engine than the ecu knows about, so its not injecting enough fuel). That could cause it to run badly, but not the fuel smell. I would say something is throwing off the readings in a way that causes it to go rich. I was about to suggest the line going to the MAP sensor, then I remembered that stock is AFM - its been too long since I had a stock car....

I'd check the AFM to make sure its not damaged. The s4-type uses a flapper to measure air flow, and incorrect orientation (such as when mounting some aftermarket cone filters) can potentially throw off the readings. It seems unlikely that would cause it to be off as much as you stated, but its worth checking.

If you look at both of the actuators, the air feed on the s5's is at the bottom so it pushes them up while on the s4's its from the top (through an air feed in the LIM fed from the split air pipe if my memory is correct) which pushes the diaphram/rod inwards.

 

Wait, I just though of something - @OP have you ever smelled a rotary run without a cat before? They are pretty diabolical. It would be easy to mistake a normal exhaust smell from a rotary - even one running lean - as having excess fuel.

Go thoroughly though all of the vac lines. Make sure any unused ports, anywhere, are capped. There are countless threads about emissions removal here. You can also search for "rats nest removal". That will detail what goes where.