riofrio

Failed again! This time my HC's were even a LOT higher (went from 800 to 1300), WTF??
My idle keeps hanging high, too. Regardless of what I do with the air adjust screw, the next time I turn it on and drive it, it will always go back to ~1200 rpms! (no surging, though.)
From time to time, the idle will go crazy if I put the tranny in gear (for example, at a stoplight).
New O2 sensor, replaced cats for a Bonez (previously used, though), replaced AFM also for a used one. TPS won't let me adjust it (I'll never see both lights on on the test rig).
I'm pissed.

bstrange99

Intake gasket, or carb spacer plate. With the hc's that high, you've probably got a pretty bad vac leak, causing the engine to starve for fuel. This is just speculation, but has proven to be the case with my 7's a few times.
Good luck

GT3_racer

I thought it was a bunch of b.s., but I ran a bottle of the synergyn system cleaner, RPX(?) though then put in one right before emisions test, passed with flying colors, cheaper and easier than searching for vac leak.

bstrange99

Maybe so, but an eratic, spaztic idle, can become a serious pain in the *** before too long, especially when it starts dying every time you stop. Use whatever you need to for passing emissions, but I would deffinately suggest fixing the problem. The gasket sets are only like $10. You'll make that up in fuel economy in the first month.

riofrio

it's the GSL-SE though. I'll look into that synergyn, but bstrange is right, I want to fix the problem too (and restore my gas mileage)

LongDuck

Are you failing the idle test or the running test? The idle CO emissions can be adjusted very minutely through the Variable Rheostat, but I don't recommend you playing with this until the rest of the TBI has been fixed. This includes resetting TPS with the test rig, setting the Idle Compensator (BACV) to work correctly, and verifying that your A/P is running pressure through the vents on the lower intake manifold.

With the readings that you're stating, this is more than likely a problem with one or more of the idle systems, unless it's only happening during the load test portion - don't know if your county requires that like here in AZ.

Get back to us, this shouldn't be too difficult to fix and get going,

riofrio

LongDuck, you always have the patience to read all these threads about idle issues and offer good advice everytime... I really appreciate it!

Well... I don't know which readings belong to which part of the test, but the guy tested it at idle for a while, and then asked me to hold 2500 rpms for about 10 seconds. The test results only had 3 numbers: HC, CO and CO2, and didnt specify whether it was for idling or running.

The Variable Rheostat (R--L pot by the AFM) has definitely been tampered with, and I have no idea if it is where it should be at. How should I take this into account when dealing with the general idle troubleshooting?

As far as the BACV goes, I've taken it apart, cleaned it, and made new gaskets, but I have not adjusted the Idle Compensator on it... how do i do this?

Have not checked air pump... will I need a pressure gauge for this? I can probably borrow one from the lab.

Is it possible the my ECU is not processing the signals properly?

I sure hope the catalytic converter is not one of the problems, cause I just put this one in.

LongDuck

I just typed out my usual HUGE response to you on this and then the forum screwed up (too busy). Give me some time to regain my patience and I'll repost...

(damnit!)

riofrio

hee hee... sure thing

LongDuck

Okay, here we go (again);

It's important to know whether the car is failing on the idle test or the load (running) test. If the idle test is where your HC is going high, then you'll need to troubleshoot the idle control stuff on the engine (detail below). If the HC's are going high during the load portion of the test (where the tech runs the engine along a curve to simulate road driving), then you'll need to look at airpump, catalyst, and other exhaust and intake related engine stuff (detail below).

Get settled in; this is going to take some time...

For idle conditions - the HC is the level of HydroCarbons that are being ejected by the engine and not burned in the cats. This could be due to an overly rich mixture, an air blockage thats causing an overly rich mixture, or a combination of factors that's leading to unburned fuel making it into the exhaust. First off, be sure that you've done all the troubleshooting around 'Idle Surging in SE' via search on this site. After that, you have a Variable Rheostat that I mentioned previously that adjusts idle QUALITY, which is controlled by idle air/fuel mixture.

Mazda FSM states the VR doesn't get adjusted unless it needs to be replaced - this being the case, you can use the VR as a last step in idle QUALITY adjustment to get a good, smooth idle condition. While I stress the use of this adjustment ONLY for idle quality, the speed is adjusted through other means.

You want to aim for an 800 rpm idle speed on the SE - any more, and you're injecting more gasoline that's going to lead to higher emissions. If you could get your car to idle at 500rpm cleanly, it would have even lower emissions, so you're going for the minimum idle speed that will allow it to idle and not die out on you.

Ensure that all the other air control systems are working well, and then lean out your VR until the engine starts to hunt just slightly - this is a lean idle condition. A rich idle condition will result in a skipping or surging idle, but only within a few hundred rpm. What you described for high rpm 'surging' is due to other factors that you'll learn about in your search.

Fix the surging and 1200 rpm idle, and you'll be well on your way to passing the idle portion of the test.

Load testing - on this portion of the test, at least in AZ, the car is run along a speed curve with the engine powering the rear wheels to simulate road drag. This results in a much more accurate reading of total emissions output. This part of the test has much higher total thresholds for output, but if you're high on this portion, it's due to the emission control system being out of whack. This includes the Air Pump (AP), the Bypass Control Valve (on the lower intake manifold), and it's associated vacuum systems.

The AP supplies fresh air to the #3 main Catalyst (the big one) so that any unburned fuel is consumed in this chamber. The previous (#1 and #2) 'monolithic' converters are primarily expansion chambers and help to break up the exhaust flow. If your AP isn't flowing air, you're not pumping fresh O2 to the main converter to burn, so you're going to end up with higher emissions at all states (idle and cruise, doesn't matter).

On the other side, if the converter is bad or damaged, no matter how much air you pump in there, it probably won't help with emissions output because you basically need a new platinum core (in a new Catalytic Converter) to get it to function as designed. Check your belt going from the crankshaft to the AP to be sure there's no slippage. AP's don't go bad, IME.

You asked about the ECU - ECU's don't go bad in 1st Gen's either. If your car is running right now, your ECU is fine.

To adjust the Idle Compensator side of the BACV, turn on all the lights, the A/C, the radio, and push your foot on the brake - this presents the highest possible electrical load on the engine, and on most cars, will drop the idle speed from 800-900 to about 500 or so. On the BACV there is a 'stalk' that sticks out toward the driver's side strut tower. On the end of the stalk is a black rubber cap that can be removed to uncover a flat-head screw - unscrew to increase idle back up to 800-900 rpm or a bit higher if you want. Replace the rubber cap to avoid dirt/grit and possible vacuum leaks.

With these things covered, or checked, at least; there are other things that you can do to help pass emissions. I've given a brief list here, but you can search on this topic to get more:

1) Inflate your tires to 40psi for the test - this reduces rolling friction of the tires and therefore requires less fuel to turn the dyno drum
2) Replace air cleaner or remove entire - REPLACE AFTER THE TEST IS OVER - this will allow more air in to displace a rich mixture
3) Change your oil - oil gets injected, clean oil burns better and cleaner than dirty oil.
3a) While you're at it, change your plugs - dirty plugs won't burn cleanly and will leave unburned fuel in the exhaust. Change your spark plug wires, cap, and rotor, if they haven't been changed in awhile - this is cheap and could net you the result that will let you pass.
4) Run the car up the freeway at 65mph for 20 minutes and then drive STRAIGHT to the test facility for the test - this will get the cats cookin' for sure and will help to burn off any unburned fuel during the test
5) Don't run your A/C, radio, lights, etc., just before the test - this takes fuel to burn to turn the alternator under load, and can 'load-up' an engine with unburned fuel.
6) Before the test, take the car to an emissions 'tuning' place and let them have a look at it - they make their money on finding out the problem and getting you to pass. Many have a money-back guarantee if you don't pass, too.

Give these things a try and report back - I still have to pass emissions testing here in AZ, and every other year I swap my stock exhaust back onto the car! My RB header and muffler is too effective to live without the rest of the year! Good luck,