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Old 10-25-2011, 03:38 AM   #1
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Post Miata obd2 monitor info Egr O2 Cat Emissions

Mods feel free to move this where ever you think it should be.

So I'm typing this up because I had an issue and resolved it. It was a huge headache and nervewrecking, and worst of all there was so little info online where the issue was resolved it wasn't very helpful. So I'm gonna put up my info and hopefully it can help someone.
I bought a 96 miata about 6 months ago with a blown motor and 180k miles on it. I towed it home and got to work. After swapping in an imported protege motor it was running real well and I was beginning to think it would be time to smog it(CA). So I brought it down and what do ya know none of the readiness monitors are "ready"besides the heated o2. That seemed normal since I only had put around 50 miles on it. So I drove it more like everyone suggested.
No go, nothing changed with about 250 miles on it. So I started investigating. From research I found it can be either an issue with the cat, issue with the o2 sensors, or an issue with the egr system. I also learned the computer looks for very specific info..more on that later. So I had just replaced the cat and front o2 sensor and I thought well maybe its the rear o2 holding the line up. so I replaced that and no change. next I cleaned out my egr valve, specifically the lower vac tube going into it. Mine was a little gunked up but I could still blow into it. so I put all that back together. and put another 100 miles on it. no go. Next i read about someone changing tps settings to factory so I reset my tps by the book using feeler gauges and my multimeter. I also found a decent sized vacuum leak at one of the injectors which was fixed by adding o rings on the end of the injectors before the isolators. At this time I also unplugged the battery in hopes just resetting EVERTHING, I have no idea if that helped or hurt but its what I did. Also My timing was set 10* this entire time. I put another 50 miles on it starting to be annoyed and nervous and still nothing, same sensors still not set. So I thought I'd try the drive cycles, even though I was pretty sure that I had done almost all the drive cycles in normal drving. After trying to follow them to a tee, I found one thing in common to most of them, and thats the 50-55 mph coast to 20 still in 5th gear NO BRAKES. So I had to look for an area to do that and after finding one, I would speed up to 55 for maybe a minute and then slow to like 15 still in gear. i did that at least 10 times. After doing that and some of the other things they reccommend I was at around 100 miles on my tripometer. so I went home the next day I drove a mountain road near my house at pretty much 55 the entire time. on the freeway ride home for 15 mins I cruise controlled at 71 mph the whole way home. By this time I had 200 miles on it and probably 5-8 cold starts. each time I drove it I would try to follow a drive cycle as closely as possible. So I basically had about 200 miles of drive cycles on it. When i checked with my scan tool the next day the o2 sensor o2 heater and catalyst monitors were all in a ready state. the egr was not. My car still passed emissions even though the guy failed me for tampering with vacuum hoses because I had disconnected and capped my cruise hose for other reasons. So i took the car to school and on my way home I went back for restest after reconnecting it and passed, this time with the egr monitor "ready". This also dropped my nox from 400 to 30 haha. So Basically this is my story on how I got my monitors to reset. I'm also going to make a checklist for anyone whos having this problem on things I would check first.

-do this drive cycle for 8-9 cold starts in a row. http://gotamiata.tumblr.com/post/166...ta-drive-cycle
make sure to COAST back down to 15-20mph in 5th gear no brake or ebrake.

-there are 2 vacuum hoses coming off the egr, find the lower one which should be all black and follow it back to the egr boost sensor. Unplug from boost sensor and blow. should be pretty easy to blow in. If not pull apart egr and clean. While its off jam some pipe cleaners or something in the holes in the intake to make sure its clear. Some newer miatas (I think 99+)have problems with those clogging.

-Check for vacuum leaks using carb cleaner/throttle body cleaner/etc.

-set timing to 10* with ten and ground jumpered. also make SURE your idle is set correctly using the air bleed screw which takes a PHILIPS head screwdriver to turn. If your not using a philips head youve got the wrong adjuster. The tach should be at about the small line below 1000rpms

-check for exhaust leaks

-use someones scan tool check the o2 voltage and water temp sensor. ie when you look at the datastream you should see anywhere from .1-.9v on the o2 sensor bank1 sensor1 while revving the car to around 2000rpms.
unplug the 1 wire from the water temp sensor at the back of the head and make sure the gauge is reading 0* see if your scantool can find a temp for the car(if not you may need a new temp sensor for the computer). If so it should be over 180* warmed up, otherwise the car isnt getting hot enough to start a drive cycle... Or if you have an aftermarket thermostat/rad. it may not be allowing the coolant to heat up past 180*/your car will stay in open loop and ignore sensors

-make sure your tps is set correctly. if anyone has ever messed with the throttle stop screw, its probably not.

-make sure your egr tube is correctly bolted to header and back of intake with no leaks. I had to make a *custom* egr tube because of my coolant reroute.

-in most states, 95-99 miatas can have 2 not ready monitors and still pass, so if you can get it that far it may pass.

-don't be afraid to spend money. Don't start replacing parts for no reason but if you have over 120,000 on the cat and o2 sensors they need replacing.

The reason the car takes so long to achieve readiness in the monitors is because the computer waits until the tps is at ___, the temp is at ____, intake air temp is at ____, engine vacuum is at _____ etc. there are so many requirements it needs fulfilled before it will begin to look at sensor data it can take a VERY long time to see all of the conditions. it also will not throw any codes for the cat/o2/egr until their readiness monitors are "ready", so just because there is no CEL doesn't mean all the sensors are functioning.

If anyone has any questions please post them here and don't pm me so others can see also. If you have any info i may have missed or suggestions please post up!! -Pops
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