I just got another 79 rx7, engine is fully stock and runs great. Got it for $850 including an extra 12a motor. In order to register the car in my name its has to pass smog. I have had it tested 3 times and each time the hydrocarbons(unburnt fuel) at idle are too high, when revved to 2K they are well below the Maximum limit, all emissions equipment are still on engine and looks exactly like my other 79, which passes smog with ease. I have put in new spark plugs and ignition coils, all are getting spark, both L and T timing are on mark, and engine is always fully warmed up before the test. Am I running too rich? Also my crankcase is not evaporating properly( release of air pressure heard when oil dipstick is pulled out) and previous owner increased OMP output(could this be the problem) Can't figure it out.

 

Lean the hell out of it. I remember when i lived in socal I spoke with a guy who worked at a smog shop, and he said that often times leaning the carb out would help older cars pass. could be wrong, though :/ Rules could have changed or he could have been feeding me **** ( I had a 71 scout II that did not need to pass smog at the time, thank god)


I don't know about the OMP output, but that might have something to do with it. block it off just for the test :p

 

The vent system being bad will generally fail you, because they test the EVAP system on all cars in the SA age range, and on SA's the EVAP and crankcase vent are interconnected. It can also make you run rich at idle/restart because it will force fuel out of your bowls shortly after you shut the engine down.

Ironically, SA's have to run a little rich in mix to get good emissions, because the thermal reactor needs a minimum amount of unburned gas entering it to stay hot enough to work. The TR burns off the richness before it's emitted. Running too lean with a TR will result in high HC's.

If you are OK at speed but failing at idle, you should check your idle mix, your evap/vent system, and your EGR. Also make sure the air pump/ACV parts are tested as detailed in the factory service manual, and that you have no breaches in your exhuast sytem heat exchanger circuit.

& don't ever block off your OMP without pre-mixing (but never pre-mix for a smog check!); you can damage seals in the length of time it takes to run a smog check. Especially if you're over-lean and therefore running drier than usual. Test it and adjust if necessary; procedure's in the FSM.

Essentially, get the SA Factory service manual, and work methodically through section 1A. If there's a fault, you'll probably find it.

Takes patience.

Looking at your bay pic, things look pretty complete as much as can be seen. Your Hot Start Assist is missing, but that won't affect emissions. Might mean other changes have been made, though.

 

I kinda figured premixed would run cleaner than regular oil, especially for the smog test. I'll remember that if I ever have to pass smog with mine :x

 

Problem with pre-mixing for smog check is that you can't adjust oil flow based on RPM like the OMP does, so you either end up with too much oil at idle (safe for the engine, but will fail smog) or too little oil at running speed (runs clean but if TOO short, you score housings or risk your apex and side seals.)

 

DivinDriver thanks for all the information, I will be sure to test vent/evap system tomorrow and make some adjustments to idle mix. I think I might be running lean and I have noticed that the engine stays very cool and takes a while to warm up.

 

If it doesnt pass again, LMK. I have a free towing service for junk RX-7s LOLLLL

 

It will pass and if if it doen't there's no way I'll give it away for free, got it for $850 has upgraded suspension, lsd diff, enkei wheels, and an extra 12a engine haven't yet taken it apart to see the condition, housings look nice and shiny from exhaust ports.

 

If the spare engine is a California build 12A (has an EGR on it & air injection passage on the exhaust port), and if you ever decide to let it go, let me know. I might be in the market.

 

like divin says with the TR system, you want to set the best idle mixture, and then go richer. also since its a THERMAL reactor it needs to be HOT.

when i bought my SA, i drove it hard to the smog shop, we pretested it and it was really clean. he shut it off for the 2 minutes between the pretest and the test test and it almost failed.

the reactor basically works by taking a RICH mixture and using HEAT to get it to burn all the extra HYDROCARBONS. and it does work very well, but it does need to be richer, rather than leaner, and it needs to be HOT.

i see the car has an 81+ engine in it, you might want to make sure the air injection passages actually connect, as the 81 emissions system is very different from the 79-80.

 

Ok I am throwing it out there,

I cheated I installed a wideband last weekend so when smog time comes around make adjustments as needed afterwards dial her back in where I like it, take the guess work out .... just sayyin

Oh and Mazdatrix has A pillar pods if you don't want to wreck the dash (I didn't) all your left with for evidance is a bunghole



freakin wacky!!! lol

 

On '79-"80 with a reactor, you need and over rich mixture to burn clean...the reactor NEEDS fuel to burn. Richen the mixture until the engine starts to slow down or not run so smooth, the turn the mixture in 1/2 -3/4 turn.

This is assuming everything else is working.