Hello all,
I just purchased my first rotary (1986 FCS4) (49K original miles) and it's a blast to drive. When I got it, it was running rough and sputtering. The previous owner had it at the smog shop and they leaned it out to pass smog, but it failed with 1.75 CO and 150 HC at the 25mph test. It sounded as if it was lean misfiring, but I'm not totally sure. It was also bucking at low rpm cruising. I ran through some tips I found on this site and the factory service manual to adjust the a/f mixture and the TPS. It runs much better, minimal sputtering at idle, smooth and plenty of power, but the exhaust smells rich. The smog shop adjusted the air flow meter, the variable resistor and the timing per previous owner in an effort to pass the smog test to no avail. It currently has newer (5k miles) precats and 1 aftermarket (7k miles) main cat. The 02 sensor is around 3k miles old. For performance parts, it's running a header, lightened flywheel, HKS foam air filter, and a underdrive pulley. This pulley has 4 timing marks but I'm not sure who makes the pulley and what the marks correspond to. I looked around on the web and found a Mazdatrix pulley which I think is marked as -10 0,10,20. I checked/cleaned the spark plugs and installed new plug wires too. Also, the previous owner told me it has a perfomance chip installed, but I've not been able to pull the CPU yet. I went thru the smog records and it appears this car has had issues in the past passing smog.
Questions:
- Does any one know if there is a normal timing mark standard for the underdrive pulleys? There is no yellow/red marks on this one, just 4 notches.
- Is it normal that the two upper plugs look a little moist (look clean) and the bottom two are tan (like a normal burn)?
- anything else I could check?

thanks

 

Ouch, you have a bit of a basket case here.

There really is no way to lean out the car except at idle with the stock ECU. This means playing with the variable resistor at the passenger shock tower, but again, this is only an idle mixture.

If someone has messed with the AFM, replace it. There is no way for you to easily set it back to stock.

Check the ECU and see if there is a "chip" installed. Since there aren't really any commonly available chips for the RX-7, it is doubtfull. However, if one is installed, then that is the first thing to swap back to stock because you have no way of knowing what was done to the fuel tables.

A full tuneup is a first step. This means all fluids, plugs, wires, filters, TPS adjustment, sensor check, injector cleaning, etc.

 

Thanks for the tips Aaron. I just pulled the ECU and sure enough it has two perfomance chips- Rotary Concepts 027x ver.1.1 and 028x ver.1.1. The chips have been in since the early 2000's and the smogs have been tough to pass since then. I forgot to add, it also has an extrude honed intake. Not sure if this mod really changes anything. I also scanned for codes and it came up clear. I used the two LED Radio Shack setup from teamfc3s.org. I will be going to the junkyard and looking for a stock ECU. I will look for a AFM as well, hopefully with the anti-tamper cap still in place.

 

Other things to consider are the condition of the main cat, smog/air pump & the solenoids related to the ACV (relief and switching solenoids). The cat and pump can be visually inspected, and the factory service manual (FSM) has simple tests for the two solenoids. The two solenoids regulate when air is directed to the exhaust ports and main cat, so while they are unlikely to fail, they play a large role in the emissions system.

 

I will check out out the solenoids as the next step. I ordered a n326 ECU from fleabay and I'm hoping this will get it back to factory spec. The main cat will be checked if the ECU and solenoids don't fix it. I may need to add a another can behind the main if needed, but currently the Nox and C02 are good (well below limit) the CO and 25 mph HC are high at this point. Too much fun.

 

We ran the car on the smog dyno at my buddies shop in pretest mode. It almost passed, but was still a little high on CO. limit is .80, but was running at .66. This is after we adjusted (clockwise to lean) the AFM, and had the variable resistor all the way to lean. Once it cooled off, I pulled the plugs. The trailing coil plugs look like they not getting as hot as the leading plugs. The leading plugs electrodes are tan, and the trailing plugs look like they have a damp carbon on them. Maybe the trailing coils are bad?

 

It's normal for the trailings to be a bit blacker. They run at a cooler temperature. Make sure that they are #9s and not #7s.

 

Folks, I wanted to update you guys on my progress. Long story short, I got it to pass smog finally. The culprit: the fuel injectors and a seal. The front rotor had a bad lower seal which was causing a vacuum leak, and the primary injector spray patterns were very poor. I had them cleaned and flow checked at mrinjector.com. 16 buck each to have them ultrasonically cleaned, new seals, and painted. Now I can finally enjoy the car! I want to thank everybody. You guys really helped me save this car from the state. They wanted to smash it and give the previous owner less than what the wheels are worth. Maybe I will put in the chipped ECU and see how it runs. Maybe save the cats for next smog check and put in a test pipe.

 

Yep, injector problems are very common at this point. 24 year old injectors which have probably been sitting for part of their life...People underestimate the impact that even 10 years of use can have on a fuel injector. I'm just about to send the injectors from my 2000 Honda Insight out for cleaning...

 

congratulation's sir

 

beyond polluton this sounds to be a very nice car