When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Soooo I know this is "very well covered" but I still don't find much info regarding what helps, what to try and how to fix it. So here I am, a simple man asking for help.
So it begins..,. I saw an add "For sale 1993 RX7 runs good but wont pass emissions" I thought pfff it's gotta be something simple.
The day I got the car it ran good but didn't seem right it also didn't boost to my pleasure.. So I tear in to it and found the spark plugs where backwards (Trailing in the leading and vice versa) So I thought booom probles solved. So I said well might as well go all out.
I went ahead and replaced the plugs, had the injectors cleaned by RC engineering, redid and replaced my vacuum lines, went through my wiring harness, replaced my fuel pulsation damper, did the "FC thermoswitch mod" added a boost gauge and tapped the water pump housing for a water temp gauge sending unit.. replaced my Pre cat with a downpie installed a Koyo radiator etc etc.
After all said and done I went to get an IM240(?) test done... It failed horribly
My results:
Actual Limit
HC 1.8 PPM 1.50
CO 33 15
Second time results where similar soooo I was desperate and ran turned the car N/A and my N/A results with two gallons of E85 and ten gallons of 85 octane fuel:
My results:
Actual Limit
HC 1.2 PPM 1.50
CO 16 15
"woooohooooo almost passed" where my thoughts " A new set of P plugs and that should do it...
Well the next day my plugs came in the mail and I drove down to the E test place with high hopes and dreams with no boost but the car failed again with similar numbers that the first time...
Now all the times that the car failed horribly they where not running the dyno fan and the last time the A/C was one... I know, I know the dam fans ( I was pissed)
I don't know what to so next other than OHM out my water temp sensor, adust tps and run more E85.
Could the A/C and the load of the car's fans coming on make that much of a difference?
I also see my air pump moving but I don't know if the clutch is doing it job.. I might not get much answers and help but I'm going to keep trying everything I can on a short "toy car" budget to make it pass and help others.
Make sure the car is hot when it's tested. The status of your injection, ignition, airpump, and cat will determine you're fate. It sounds like you've got the first two covered. The precat definitely helps, but people pass without it. Some people will dilute with ethanol, with mixed results.
I was surprised to see that a precat made no difference in my smog tests; that's not to say it wouldn't help you, however.
What did help was a new O2 sensor. The smog tests in CA are done on a dyno and the [stock] ecu will be in closed loop--so it had dramatic affect.
If your tests are at idle, then check the ACV valve assy and it's controls closely. It has a failure mode that wont provide proper port air--which is essential to pass at idle. (Air to just the main cat at idle will likely not be sufficient to pass. And you also need PORT air injection for the precat to fully function.)
Good luck!
Last edited by Speed of light; 08-05-15 at 01:18 AM.
Believe the pre-cat is only for a cold engine. If it's hot, the main cat is sufficient. OP is silent on the air pump and main cat. The air pump is essential and stock main cat is a close second. Another thing to check is the fuel catch tank under the TB. Sometimes that dumps fuel at inopportune times and best to purge it prior to a test. Other things not mentioned that could affect the results are porting and aftermarket ECU
Okay guys I have read all of your replies and I apreciate the responses and the total lack of "flaming" it's nice to see helpful replies.
So I went in today for a retest after doing an oil change, but before I post pictures I'd like to give you guys some background about my cars and myself.
I have owned about 12 rx7's. One firts gen and several FC's including TII's and one (My current rx7) FD3S I have done all my work myself. From engine rebuilding to soldering and patching harnesses. All of my cars have always passed the IM240 test without hiccups. I could register the FD in a different county and be done with the ordeal but I want it to pass for some reason.
Now, after going through everything on the FD it runs and drives amazing putting downs some serious stock performance.
Now I had a TII with a downpipe and 2-stroke and the car passed with flying colors. 2-stroke was dosed at 1OZ:Gallon of gasoline.
Now the FD seems to have proper compression, but I have not done a compression test yet. But given it almost passed once I don't think there's a problem in that regard.
I have tested my TPS all V+ specs are withing range, oil is new and has new plugs. I have the car setup N/A and is easily reversible in 20 minutes to the glorious twins.
Now when I almost passed I had put in 2 gallons of E85 in an almost empty tank and topped it off with ~10 gallons of 85 octane (Burns quicker and cleaner) on the latest run the car had plenty of drive time to warm up the cats but did far worse.
I know that E85 doesn't have ideal lube properties although it's quite a small amount.... None the less could it rinse away the precious oil film, lowering my compression? I ask because while I turned the engine to check the spark quality (Spark seems good with solid blue color) the engine didn't seem to have that familiar resistance other 13b's had when turned by hand. I took out the L plugs and cranked the engine and it sounded healthy then I proceeded to add some oil through the spark plug holes and turned by had. Resistance while turning by hand increased and sound seemed better while cranking.
Any ways here's the pics of my E tests and some info.
The second test I got. Running boost, 91 octane and some left over premix. Dyno fan was not on. Plugs had ~2800 miles. downpie
Different test, still boosting and still doing 91 octane with ~2 gallons of E85 and premix dyno fan still not on (wtf guys?) oil getting dirty but fuel catch can was capped
Finally, a breath of hope.. SOO close. This is when I did the N/A mod, running same plugs, dirty oil, small vacuum leak, 2 gallons e85, 10 of regular fuel (85 octane) small drive so cat wasn't too warm. Downpipe but they finally had the dyno fan running
The day after all the same but new plugs, they didn't turn on the dyno fan and the A/C was running
This one was today same as above conditions but A/C was off, dyno fan was running, added ~1.2 gallons of e85 and some regular. Did way worse then ever.
Here's an interesting one for me.. My fuel catch can had fuel! I disregarded it the first time but wow look at those flames. This is my next step since this is as well know as a culprit.
After this a new cat will bu used but for now I am determined. If all esle fails I will give in a register in another county.,
you need to look at or replace the o2 sensor, and then make sure the air injection is actually delivering air to the right place.
btw the E85 looks like it hurts more than it helps
^
This.
The rear bed of the cat is the oxidizer part that impacts HC and CO. You need to make sure that the airpump system is properly switching the airpump output to the rear bed during cruise conditions, which is what is happening for the IM240 (as well as confirming that the airpump is actually outputting air). I don't remember if the IM240 has an idle mode or not, if it does then not having air directed to the engine port at idle could also be causing high HC and CO, so again the ACV system.
A lazy O2 sensor can also exacerbate this condition.
If all of the above is working correctly and you are running a stock ECM with stock injectors, then my guess is that you need to look at getting a replacement OEM catalyst.
assuming the O2 sensor is ok, this is a secondary air/ACV problem. You need the air pump injecting air into the exhaust ports for idle and most low load conditions. That's why your CO is so high but your NOx is low.
assuming the O2 sensor is ok, this is a secondary air/ACV problem. You need the air pump injecting air into the exhaust ports for idle and most low load conditions. That's why your CO is so high but your NOx is low.
I do have a spare air pump from an automatic block I bough a while back, I don't know if my pump is working properly and honestly don't know how to test it. I have searched and most results are for the "moo" sound problem.
Is there a way I can bypass the wiring and have it running all the time?
I have a feeling my air pump might have something to do, but I don't have a good baseline to compare to for example a test sheet where an air pump wasn't used or known to be bad.
Any ways I am thinking of routing the turbos back so it's boosting. I know the test guy likes to get on the turbos so I don't know if this is a wise move yet.
The rear bed of the cat is the oxidizer part that impacts HC and CO. You need to make sure that the airpump system is properly switching the airpump output to the rear bed during cruise conditions, which is what is happening for the IM240 (as well as confirming that the airpump is actually outputting air). I don't remember if the IM240 has an idle mode or not, if it does then not having air directed to the engine port at idle could also be causing high HC and CO, so again the ACV system.
A lazy O2 sensor can also exacerbate this condition.
If all of the above is working correctly and you are running a stock ECM with stock injectors, then my guess is that you need to look at getting a replacement OEM catalyst.
Good point. I checked basic air pump clutch engagement by disconecting and re conectoing the (-) battery cable and trying to turn the inner pulley. I still have to check if it supplies air with the engine running. I might have a problem within my ACV as well.
You need to replace the rear cat. I had the same problem 5 years ago. After replacing it my readings are HC 0.1884 CO 2.1501 NOx 0.6484
That's what I'm hoping for. I see you're in Boulder as well. Could you tell me what brand catalytic converter you used? Do you still have an rx7?
This thing is driving me insane but a catalyst would make sense and it can't hurt.
Looking at your numbers though... Would it have been HC 18.44, CO 2.1501? If that was the results my car would still fail. I think they might have tightened the threshold. HC limits are 1.5ppm and CO is 15.00
You are going to need an OEM cat, even a new aftermarket cat is not going to get emissions low enough. All the aftermarket cats use basically the same small can size, the OEM cat is probably 5 times the size and is much more effective. Mazda doesn't sell new ones anymore, you will need to find a lower mile used one.
A bit confused here about the units given in the emission test results for Colorado. In CA they use parts per million (ppm) for HC and CO, as you can see from my post (#8) above. But the OP's numbers are given in GPM, which I presume means grams per mile. So how do you convert one to the other to compare?
Also, at one time years ago, I had replaced the cat in our car due to failed emissions, but I made the mistake of buying and installing an aftermarket unit. The emissions got worse. So I had to revert to a new OEM cat, which cost about $1300. But that fixed the problem semi-permanently (at least) as you can see from our car's test results in 2010, 2012, and 2014.
Fwiw, I have repeatedly passed CA emissions with a high mileage stock cat (>160,000mi) that was in good condition and still worked. No precat. Working air pump & ACV. And with a very large street port to boot--so it's do-able.
There is a good must read treatise on the FD emissions system: the air pump, ACV and cats in Mazda's 1993 Service Highlights publication that discusses the acv operation in detail with diagrams, descriptions, air delivery schedules, etc..
The other thing I want to mention is that the later stock ecu's will cut of the air pump after a minute or two of operation at cruise (presumably to prevent cat overheating). I think they all turn the airpump off above about 3000 RPM, so you have to watch for that during testing.
I had the "switching valve" diaphram fail in my original ACV at around 200,000 mi., which jacked me up for one smog test. Once I got that sorted, it passed again. Get a mighty vac and check all the solenoids and servos associated with your ACV (in addition to verifying the cat, air pump and O2 sensor as has been mentioned).
Last edited by Speed of light; 08-07-15 at 12:53 PM.
That thread talks about how the air pump works, drawing on service highlights info.
Also, page f-119 of the service manual shows how to check air pump pressure and check valves. Maybe the air pump clutch failed. If the switching actuator has vacuum on it there should be secondary air flowing through to the exhaust ports.
If Mazda doesn't sell new cats I'd rather get a good aftermarket unit, such as Bonez althoug I have had excellent look with Magnaflow/Ebay cat convereters on my last rx7. My car only has 70,000 miles so I'd rather not buy a used cat. Now I'm not quite sure if this is a good indicator or not but less than a 1000 miles ago I installed my downpipe and took a peak at the cat media which looked intact. I guess I could take it off and take a good look at it. I also have a infrared thermometer so I could check it with that.
Regardless a new cat is due but I highly suspect something isn't doing it job. Given that I almost passed one time and am mostly failing others it could be a problem with my solenoids or my ACV...
*Sigh* I suppose I'm going to have to remove the UIM and test all my solenoids again, which I'm sure I did last time with Ohm testing etc. but I could have overlooked something.
I'll see how it goes I guess. I'd like to pass the test and share with others, as I know many have the same problem.
I'll cob through the FSM and see if it gives me ideas.
08-04-15, 06:38 PM
My ongoing emissions thread.
