It's nice being able to ask this in a flame-free environment.

It was suggested that my FD might be running rich. My idle is lumpy and I bombed my emissions test.

How do I test to see if my FD is running rich? I have no mods, 16,000km on a rebuilt 13b.

 

So you still have stock ecu? Sounds like you need new plugs.

 

I like to act on evidence, not suggestions.

a wideband lambda probe tells your this instantly, and once you KNOW, you can act accordingly.

Ask if someone close to you has a loose wideband probe and gauge around, clamp it to your exhaust pipe, let wire run to loose gauge in car, and go for a ride. Check AF on cruise and WOT, and report back.

Also, more info on your build would be awesome, as it is now, it can be anything from stuck injectors, to **** plugs, to **** map on an aftermarket ECU etc....

 

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if its on stock ECU not much you can do to adjust it ..

do you have a CEL ?

how new are your plugs?

have your cats ever been changed ?

O2 sensors?

the FD idles rich by nature due to it being a rotary .

the only real way to know is to plug in a wide band . But honestly if you are running a completely stock car with stock ECU its more about getting the car into good shape rather then wasting money on a wideband when you cant adjust the tune on the stock ecu .

Good luck!

 

Real good tell tale is fuel economy. I get 16-18 city, 21-22mpg highway. Even a slight difference will drop fuel economy.

If it is running rich, could be a problem with the fuel pressure regulator, stock O2 sensor, or plugs. You can't adjust the fuel with a stock ECU, but you can find what input is making the stock ECU run too much fuel.

Dale

 

Yes, stock ECU.

I'm at 16mpg mixed, so I guess I'm not that far off the mark.

I'll probably take the car to Mazdees and have them troubleshoot the bouncing idle - seeing as that's my main issue and I can't adjust the mixture with the stock ECU anyway.


Thanks guys, I appreciate your input.

 

^Seriously pull and inspect the plugs before taking a 20+ yr old car to a dealer where no mechanic probably has experience with. If they can't hook up a obd II scanner to it, they will be clueless. On a stock rotary, the plugs cause all sorts of issues if there fouled.

 

lol forgot I wasn't in the Canadian Forum - Mazdees is our Rotary Specialist. They're the ones who rebuilt my engine in the first place, but thank you I will pull and inspect the plugs just the same in an effort to save some scratch.

 

Please scan and post the emissions report from your failed test. Knowing how to interpret them will give very strong clues as to what's wrong with your car. How are the tests performed? Do the idle car and put a tailpipe sniffer on it, and then run it at a couple steady speeds?

A wideband would be great, but you don't need a wideband to know if you are running rich from the perspective of an emissions test. The tailpipe CO% will tell you. Your tailpipe emissions should be basically 0 if everything is working right.

 

I recently installed a wideband O2 sensor and permanent gauge in my vehicle as I think my car might be running pig rich. Can't wait to try it out. My odometer does not work and have not had a chance to deal with that yet. I wish we had emission testing in my state just so I can have an excuse to get a gas analyzer. They tell you so much about the health of your vehicle. Please do post the results.

If you are worried about it I suggest you install one too!

 

No, you really don't .

Widebands are DIRT cheap now, I think the LC-1 with a gauge is like $180 or so. But, with a near stock car, bad fuel economy is moreso the result of needing a tuneup more often than not. New O2 sensor, new plugs.

Or if you're just driving like a dumbass. I've seen people drive full throttle all the time, cruise at 4500 RPM, etc. Yeah, it's fun to hit the throttle, but come on. You don't have to hyper-mile it, but just drive normal.

Dale

 

This;


It's a two speed test - idle and 2500RPM

2500RMP
HC (ppm) 629
CO(%) 7.34
Dilution % 17.44 (pass)

Idle
HC (ppm) 4213
CO(%) 6.72
Dilution % 16.72 (pass)

 

No NOx reading? Either way, you probably have a bad cat, and you need to check to see that your port air (part of the air pump system) is working.

If we had NOx it would be easier to tell, but basically your emissions conversion efficiency is practically 0. You can tell that from the very high HC. The high HC means poor conversion, rich mixture, or misfire. The high CO means rich mixture at the very least.

The fact that your idle is lumpy indicates to me that you should set your idle speed according to service manual procedure, and check your air pump and port air system. That system directs fresh air into the exhaust port (not the tube to the cat, that tube actually doesn't do a whole lot on an emissions test). If the plugs were changed when the engine was rebuilt they're probably not the problem.

 

i bet the air pump and or ACV isn't working. if some shop just rebuilt it they probably crossed a vacuum line or swapped the housings front and rear (which blocks off the port air injection).

if the air pump WAS functional, the HC and CO would be lower, even with no cat.

 

LOL.... You are so right actually.

 

Kinda an overkill on a stock setup... The smog results will tell him a heck of a lot more info than a wideband actually.

Edit- looks like smog results and advice has been posted already

 

Thanks for your help guys, I appreciate it.