What do you think of these emissions results? (Page 1/2)
Modesto SEP 03, 11:25 PM
As you can see the only thing that failed was hydrocarbons at idle.



I'm trying get a tune from Sinister Performance, but having a hard time logging data (WinALDL w/USB, which the cable supplier said shouldn't present any problems, but all it will log is raw data that looks totally inaccurate anyway). How do these numbers compare with what you guys have found? Bear in mind, this was on a semi-built 3.4, but I'm interested to hear.
theogre SEP 04, 02:03 PM
This is a typical 2 speed test w/ sniffer in tail pipe.

Many GM cars barely pass at Idle.
I bet you'll find BLM is pegged at idle. Only reason not tripping MIL light is because Integrator and maybe other sensors doesn't pegged long enough to set a DTC.
See my Cave, Scan Tool Help

Numbers above are often Worse if have no or cold cat or cat w/ problems because part of 2 step test is trying to find a dead/no cat car.
Even when you run the car on the highway then idle for a long time or shut down for just a minute or three, the cat can be too cold to work at test time. This is why some inspection places have big signs to "park and run car a fast idle" (paraphrase) to avoid E-test fails.

Note that most testers have an ignition "pickup" to read RPM. Many inspectors put this on the front of Fiero and make it hard to test. I get this every time I go and have hard time to pass because pickup fails. This will fail too but not failing for counting numbers.

Likely issues causing Fail...
Engine has problems. quick examples If has HEI has can have problem w/ base timing, iffy FI, iffy Fuel Pressure, has no/cold cat or all.
WinALDL and others scanning ECM often lies to you when you're trying "engine tuning" because OBD1 and early OBD2 ECM in "Scan Mode" isn't fast enough to read many sensors in "real time." GM et al Never tunes a motor based only on ALDL data stream because of this. Most manufacturers won't tune using this at all and programing is done w/ engine dyno data and a lot more expensive tools.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Modesto SEP 04, 05:46 PM
That's really interesting! I did find out this morning that its throwing the IAC and TPS codes, but I haven't done any testing to see if they are functioning properly. It's odd because it idles smoothly and has great power, just a bit rich at idle. I'm hoping that I can get it solved between those two potential issues and then just dyno it to make sure my AFR is in a comfortable spot.
theogre SEP 04, 06:12 PM

quote
Originally posted by Modesto:
That's really interesting! I did find out this morning that its throwing the IAC and TPS codes...

Maybe 1 or both dead... Possible you messed up the hard idle stop w/ both codes.
Fiero V6 TB and others use same or almost same reset method as Fiero V6 in my Cave, Idle Stop

Anything else like bad cable or pedal parts can act as a stop screw cause same problems.
Notorio SEP 04, 07:37 PM

quote
Originally posted by Modesto:

Bear in mind, this was on a semi-built 3.4, but I'm interested to hear.



What are your mods?
pmbrunelle SEP 04, 08:24 PM
I suppose that excess camshaft overlap won't help with this.
Also there could be crevices where air/fuel mixture can be trapped and left unburned. Maybe in the the piston-to-bore gap?

Anyway, those are things that are hard to change on an assembled engine.

Perhaps some easier things to try / ponder. I am brainstorming here:

Try a hotter thermostat

Change the oil immediately before the test to remove any HC it may contain. Also could use greater viscosity so that less oil ends up in the combustion chamber.

Does the idle RPM have to be within some certain limits to pass the test? If not, you can try raising the idle speed, either with a chip, or by messing with the screw (count turns so you can return it to its original setting).

Spike the fuel tank with E85, then drive around some time to get the BLMs adjusted for your new fuel.

Possibly a new oxygen sensor; if yours happens to read lean, the mixture will be (incorrectly) enriched.

Potentially you could retard the ignition timing 5° or so; this place here says that HC increases with timing advance:
https://ijritcc.org/downloa...82908_21-03-2017.pdf
Edit: there is a contradiction. They say one thing on the first page, but something else in the graphic later on.

I think the ideal is to pay for live measurements as you try out stuff. Then, you can determine what works, and then succeed at the real test.

[This message has been edited by pmbrunelle (edited 09-04-2020).]

theogre SEP 05, 12:22 AM

quote
Originally posted by pmbrunelle:
Does the idle RPM have to be within some certain limits to pass the test?

Yes. Both speeds must be w/in a narrow window of RPM or instant Fail. Exact range for each step is up to state rules. This test method is still use by several states for anyone driving OBD1 and older as a daily ride.

Higher idle Won't fix the problem because reading is 3+ times the limit.
Only when you fail a numbers like 220 limit but reads ~ 225, bumping the to just under idle speed limit might pass.

Running E85 may Fail too.
Ethanol adds O2 same as MTBE did and now "banned" in many places.
If added O2 from E85 or car w/ exhaust problems then Sniffier can/will "see" and "trip" error (Often called "Exhaust Dilution" error) and you Fail. If Inspectors think you "cheated" w/ that error then can cause a lot more expensive legal problems than just fail your car.
Modesto SEP 05, 09:34 AM
Good thoughts and more to potentially look into... The 3.4 has the Crane 272, ported exhaust, and a bunch of reliability upgrades like roller tipped rockers, etc.
pmbrunelle SEP 05, 12:25 PM

quote
Originally posted by Modesto:
reliability upgrades like roller tipped rockers



Honest Don and myself had problems with Comp Cams Magnum roller-tipped rockers when used with grooved pivot balls... your mileage may vary.
Modesto SEP 05, 09:52 PM
I'm an idoit. I mistook the code 12 for TPS, so it was just a code 35. I remembered that I never reset the computer after finding the EGR solenoid vac line not connected, so I reset it tonight. After 10 min of idle and a 5 min drive it still wasn't showing. I'll drive it a bit more and see of the code 35 shows back up. If not I'll take it to be tested again.