Smog nazis and HC

[FTA1995]

Looks like I have way more issues than described here. I have no idea what's wrong besides saying the tune is off, or guesing at other stuff. Oh and looks like the MAF readings are good now. Idle shows mid 12s now, so I think the readings were just weird circumstances that day.

This morning, however, it took about 5 minutes to start. It sat there cranking and cranking, once in a blue moom, it would catch for a very minute split second. Well eventually, I would then try to hit the throttle during this time - and that's how it got started. It seems to be driving rough in open loop, and here are stats from a scan:
- First part of my commute, IAC counts were 150-160 at 60 MPH. Second part was 110 at 60 MPH. IAC at idle is around 65-75. Does this sound right, or do I need to adjust the stop screw?
- BLMs are not looking good. They are 160/150ish for cells 2, 3, 16, 18. They are high 150/140s for cells 5, 6, 7, 9, 10, 11, 18 (sometimes 160, sometimes 150). The dyno tuner, using a wideband at the exhaust tip, said I was running to rich at part throttle so he leaned it out a bit. So it appears that this leaning out made the car raise the BLMs to add more fuel?
- Seeing tons of knock, but the tuner programmed knock retard to be minimum. I think the knock is sign of an exhaust leak?

I'm not sure what other value I should look at to further diagnose the issues. Thanks in advance for any help.

Is the PCM pulling its max knock retard all the time?
Were your start up enrichment tables changed?
Possibly a bad batch of fuel?
An exhaust leak can't cause engine knock directly, but if you have a leak, and the fresh air is getting drawn into the system, that would cause your high block learn counts, the o2 sensor sees this is being WAY to lean.
Make sure its knock and not a small leak just popping at you every once in a while.
Knock counts are going up all the time just idling?
That would be a sign of a good spark knock, assuming your fuel is good for the compression you have.
cheap test: Throw a full bottle of stabilizer or octane booster in there,
If the knock count goes down or the retard lessens, its real knock, and that could get nasty with all the different problems you're experiencing.
Whats your base timing and fuel you use?
150-160 IAC steps at 60 mph... how much cfm does your engine suck?

Mine takes a max of 99 steps(that i can see) on the scanner.

If you got a BIN file of the ecu send it to me if you want, i'll look at it.

[Craig 94 TA GT]

Is the PCM pulling its max knock retard all the time?
Were your start up enrichment tables changed?
Possibly a bad batch of fuel?
An exhaust leak can't cause engine knock directly, but if you have a leak, and the fresh air is getting drawn into the system, that would cause your high block learn counts, the o2 sensor sees this is being WAY to lean.
Make sure its knock and not a small leak just popping at you every once in a while.
Knock counts are going up all the time just idling?
That would be a sign of a good spark knock, assuming your fuel is good for the compression you have.
cheap test: Throw a full bottle of stabilizer or octane booster in there,
If the knock count goes down or the retard lessens, its real knock, and that could get nasty with all the different problems you're experiencing.
Whats your base timing and fuel you use?
150-160 IAC steps at 60 mph... how much cfm does your engine suck?

Mine takes a max of 99 steps(that i can see) on the scanner.

If you got a BIN file of the ecu send it to me if you want, i'll look at it.

Thanks for the reply.

The PCM is not pulling any knock retard because it looks like the tuner programmed it out completely. I'm just looking at the knock count in general.

I have no idea about startup enrichment tables - I don't think he touched them, but I could be wrong. I haven't hard cold start issues yet though, until today. So it could be something like a fuel filter going bad? I'll try to do a fuel pressure test later.

The exhaust leak can cause false knock because it's so loud - that and the RRs with stock valve covers. All that noise can even trick an LT4 KM into thinking it's knocking when it's just noisy - I have experienced that too many times. However, about the exhaust leak and the false lean condition - I know that's a major issue and I don't know what to do anymore because these SLPs are the only smog legal 1 3/4" headers. Maybe it's time for some long tubes without any lettering and just say they're SLPs.

Knock counts only go up during acceleration - I would guess as the motor gets louder, the leak gets louder.

Base timing was around 31 degrees I thought. A scan shows 27* at idle, and 31* around 1250 RPM. I can get more info on this and maybe post the LT1edit chart. The best fuel I can get is 76 brand 91 octane CA MTBE fuel.

I adjusted the stop screw on the TB and maybe set the IAC counts too high. I should maybe open the TB blades more at idle to lower the IAC counts? Sometimes it's very very slow to adjust the #s going from 2500 RPM to idle. I don't know how many CFM the engine sucks, but the TB is 58mm and the heads flow 290 CFM at .7, and about 285 CFM for my cam lift.

Can you read LT1edit files? I can get a BIN file, but I have the LT1edit file on-hand already. I can use Tunercat to get the .BIN, but I've been using LT1edit and I think they're in different formats.

[FTA1995]

Well, If the leak is loud enough at the right frequency it could definitely be
picked up as real knock. I'm pretty sure it would have to be very loud to do that though, I've had a few leaks in my history, the only one loud enough to get some false knock retard was open headers.The best way to tell is to watch the knock count with an extended idle. If i stays at, let say 2383 after startup all the way through a full therm cycle it should be ok, even if theres a few little dings maybe every couple minutes it shouldnt be THAT bad. I mean, if you're getting these symptoms of knock at idle with no load and its warmed up...
You really need to put some higher octane fuel in there, see if that fixes the problem. If theres no more knock, then its probably the fuel OR POSSIBLY the advance at idle.


Bin or .lt1 will do fine either way.
I have a nice little DOS app that converts .lt1 files to .bin files with no trouble.

I'll PM you my email address check your inbox.

[FTA1995]

Hey after looking at everything, I couldn't see anything strange, at least that would be causing some of your problems, any DTC's?
You should be running at a good AFR with this and those injectors paired.
Is it possible 1-4 of the injectors is out on one side?
That would justify the BLM's being so high, freaking out because on bank is getting what it sees as NO fuel relatively speaking.
First check the injectors with the old long flat head screwdriver trick.
If not that, check those O2's out.
If still not that go to the rest of the feedback system.
Let me know what you find out!
Also, some of the EGR swtiches and constants are disabled, but not all of them.
It's possible that the EGR spark table could come into play, i would just zero it out to make sure, that might also be why you're not passing emissions.
This sounds more like a hardware than a software diagnostic and I can't really be there in NJ to help, wish I could!

[Craig 94 TA GT]

Thanks man, I'll check out all of those things.

I also just talked to the dyno tuner and told him that the filter was so dirty and clogged - he replied "Yea that filter can skew the tune big time." So maybe I'll get it retuned and see from there.

[FTA1995]

Thats probably the best bet, I didn't realize you had that dirty filter for the tune. Too much restriction can definitely throw a tune too lean.
to see if it is take some duct tape and slowly block off the filter in 1 inch intervals.
If you get it to around the same flow rate as it was with the dirty filter and your problems go away, there's your answer!

[Injuneer]

"knock count" is not an absolute value, and incrementing knock count does not mean the PCM is picking up knock from the knock sensor. Knock count is a field that starts at 0, increments based on the PCM observing conditions that MAY cause knock, and will eventually reset to "0" when it reaches tha max value for the field (~64,000). Knock count is a value calculated by the PCM based on engine operating conditions. The important number is not the actual knock count, but how fast the value is increasing. It is not unusual for the knock count to increment up several thousand counts on cold start. In and of itself, knock count does not generally cause knock retard.

The PCM appears to ignore incrementing knock counts, until it observes a significant level of feedback from the knock sensor. Once that happens, it appears to trigger a flag that allows both incrementing knock count and knock sensor signals to cause knock retard.

While a dirty air filter can cause performance loss, in a mass-air system, it should not affect the A/F ratio. The reduced air flow will be picked up by the MAF sensor, and the PCM will provide a reduced fuel flow. 12gps at idle seems excessive. What is the idle RPM? My stock tune typically showed values of 6.0gps at 800rpm idle.

[FTA1995]

Yea I had the same with my stock tune, what if the tuner adjusted the MAF tables?
If he did that with the dirty filter to reflect what it should have, that would definitely cause a high read on the MAF...
Just a thought

[FTA1995]

Actually, now that i think about it, those problems are really REALLY similar to when i had a MAF here to test it for a friend.

the resistors had been brought to a temperature much higher than usual by a soldering gun

for whatever reason..

ANYWAY, I noticed that sometimes it would start up, but then die out very very quickly, and the MAF reading at idle was about 15 grams.
It didn't throw a code unless we got it on the street at a 1800 rpm cruise.

Unplug it and see if it runs right. Best way to tell if the MAF is the only culprit.

[Injuneer]

The OBD-I PCM does not set a code for irrational flow values. The flow value rationallity check (MAF within 40% of the speed-density calculation at low flow, 25% at high flow) was only added in OBD-II. The only check in OBD-I is for a complete circuit to the MAF.

[FTA1995]

The OBD-I PCM does not set a code for irrational flow values. The flow value rationallity check (MAF within 40% of the speed-density calculation at low flow, 25% at high flow) was only added in OBD-II. The only check in OBD-I is for a complete circuit to the MAF.

I swear, my system will pop the MAF dysfunction code when a MAF is plugged in with a great connection with a very bad MAF.

BUT it will only throw a code IF the sensor is horribly wrong.

Given, yes, it isn't an "I'm seeing erroneous flow rates" message from the PCM, but its still something.

In the OBD I systems, its easiest from my experience with GM MAF's to just unplug them to see if thats where your trouble is at for the idle, assuming there arent any other systems in question.

Give that a shot yet Craig?

[Craig 94 TA GT]

Sorry for dropping off - I had finals this week and have been so busy with work - hadn't had a chance to do anything to the car.

I made a chart to represent the air flow vs RPM for the engine. Desired idle is set to 800 RPM for hot idle, in gear. It seems to flucuate between 775 and 825. Based on a the data, the lowest it ever got was 10.19 GPS. The highest at idle was around 13 at 825 idle. The average seems to be around 11-12 gps. The MAF is a new "LS1" type (but looks identical), which Delco claims is the new part # for our LT1s. It has never been modified and the screen is still on. I don't know if you can tell anything from the graphs attached, but it appears that the GPS is slightly raised on average. Both are graphs from my daily commute. I should have had WOT comparisons though, but I do not.

I'll probably try to get it smogged again in the next few days.

I also noticed that the "cold hard starting" is happening again. It happens when it's cold outside, the 2nd time firing it up after about 10-20 minutes. I haven't had a chance to figure that one out yet, but I'll worry about it when I fix the rest first.

[FTA1995]

Mine starts like crap when its below 20 deg, but than again what doesn't.

I think your MAF is jazzed up,
Notice in the graph before you cleaned the filter, the lowest rpm is also the lowest. I boxed it on the second graph and first where the interesting difference is.

also, I'm guessing that these graphs were not done exactly the same as far as logging. The two outliers in the first graph are the start and finish on the RPM scale, which is a bit strange unless its just a graph glitch.
but the big thing that I noticed was the MAF drop off at about 775 rpm to about 900 rpm. Unless this will directly correlate with your idle over/underspeed ret/adv, I think the maf is bad. Try to see what the idle timing is. If its 20 dbtdc, for example, it shouldnt run more than + - 2 deg if its within + - 50 RPM of desired idle.

Try unplugging the MAF and see what happens. If it idles better, try that.
Its also possible that you have a stuck IAC valve, or even just a bad opti.

[Craig 94 TA GT]

Well, back to the original subject real quick...

I took it for a 3rd try today and it passed!!!!!

It's running cleaner than prior to the heads/cam. Here are the numbers:
15 mph (1794 RPM)
CO2%: 14.2
O2%: 1.07
HC max: 83
HC ave: 21
HC measured: 28
CO max: 0.48
CO ave: 0.06
CO measured: .12
NO (PPM) max: 689
NO ave: 150
NO measured: 410

25 mph (1740 RPM)
CO%: 14.1
O2%: 1.10
HC max: 48
HC ave: 13
HC measured: 33
CO max: 0.46
CO ave: 0.05
CO measured: 0.12
NO (PPM) max: 706
NO ave: 136
NO measured: 353

What I did exactly was:
- Cleaned the horribly dirty K&N on the Moroso CAI (as mentioned above)
- Cleaned MAF
- Changed the fan programming to close to stock. The PCM had 180 primary/187 secondary. I changed it to 222 primary/232 secondary, roughly 4 degrees below stock.
- New alternator that outputs good voltage now (previous one was reading out 11.9 to 12.3 on a scan)
- Drove it 15 miles around town and freeway to make sure it was fully warm

The tech was amazed that I cut HC in half. I'm amazed I even cut NOx down slightly when it's running hot. Prior to the new motor/heads/cam/stall, my readings were:
15 mph (1967 RPM)
CO%: 14.3
O2%: 0.7
HC max: 83
HC ave: 21
HC measured: 60
CO max: 0.48
CO ave: 0.06
CO measured: .02
NO (PPM) max: 689
NO ave: 150
NO measured: 653

25 mph (1496 RPM)
CO%: 14.4
O2%: 0.5
HC max: 48
HC ave: 13
HC measured: 36
CO max: 0.46
CO ave: 0.05
CO measured: 0.00
NO (PPM) max: 706
NO ave: 136
NO measured: 582

That was with all bolt-ons and a stock tune. For reference, my smog before that, I had some minor bolt-ons minus the SLP headers/Carsound cat, 9" rear, and the smog results were
15 mph (1343 RPM)
CO%: 15.1
O2%: 0.3
HC max: 83
HC ave: 21
HC measured: 9
CO max: 0.48
CO ave: 0.06
CO measured: .03
NO (PPM) max: 689
NO ave: 150
NO measured: 260

25 mph (1496 RPM)
CO%: 15.2
O2%: 0.3
HC max: 48
HC ave: 13
HC measured: 2
CO max: 0.46
CO ave: 0.05
CO measured: 0.00
NO (PPM) max: 706
NO ave: 136
NO measured: 320

I noticed a trend: mods go up, O2% goes up, but CO% does down? I don't know what this means?

[Injuneer]

The O2 in the air combines with the C in the gasoline. If there isn't much O2 available (rich mixture), the combustion is not complete, and the C + O = CO (carbon monoxide). If there is an excess of O2 (lean mixture), the combustion is complete, and the equation is C + 2O = CO2 (carbon dioxide). The more O2 that is present, the lower the CO and the higher the CO2.

The other part of the combustion equation is the "H" portion of the hydrocarbons (fuel). 2H + O = H2O.

At low combustion temperatures, the "N2" is just along for the ride.... it does not take part in the combustion process. But as combustion temperatures increase, and with a surplus of O2, the N + O starts to combine and form various oxides of nitrogen (refered to as NOx for convenience).