Help! failed smog AGAIN

[boomdriver]

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Alright.....this is war !

As if I did'nt have other things to do. After finding at least 5 things that could have been responsible for the 1st smog failure, and correcting each and every one AND doing a major tune up, I felt confident about the retest.
Failed with only slightly better numbers than last time.
Whats been done so far:
NEW wires, delco plugs, cap & rotor. New IAC. reset TPS and ign timing. R&R throttle body to clean and install new gaskets,. Ran alcohol blend thru test.

Checked each fuel injector. 6 were at 17.0 and 2 were @ 16.9 Nowhere near faulty. Fuel pressure is 37lbs and holds for 1/2hr before dropping.

The ONLY things left are the Cat and/or the o2 sensor which I cannot break loose....

Any suggestions? I am at a loss.
The texas smog test are rigged....anything that 96 or newer gets smogged off its own OBD-II system. Anything under 1996 gets the dyno and I've been told that the spec is MUCH harder to achieve on top of the smog machines NOT being maintained and calibrated as often as they should be due to the cost of that maintinence.
All well & good, I still need a smog cert ! ! !;help

 

[BigJimZ16]

Post the results so we can help... If we can't see data, we'll be shooting in the dark as it seems you've been doing.

 

[Schrade]

Get a data scan from any shop, and post it up.

How much booze did you load up? Short of cleaning up the bad burn, you really have to tank it up . Close to E85 strength. That will heat up the burn, lower the HC's, and raise the NOx's. You need to advance timing a few degrees too to heat up combustion. That will raise NOx's, but you had lots of room to spare in your first scan...

 

[boomdriver]

It was running on 1qt methanol:3 gal 93 oct gasoline. Not horribly thin but that should have been enough....

I spoke to the area performance "guru" this afternoon and he WAS a smog inspector until he got busted...but he still had a wealth of info regarding Tex smog test. This guy walked me around the Viper that he was adding twin turbo's to while we talked. His shop also had 3 Hayabusas, one turbo'd and a couple late model vettes....so I'm comfortable with his advise.

He says that an engine that had mods, even moderate mods will ruin the average catalytic converters ability to react chemically within a few weeks if the engine has a rich condition from tuning or malfunction. It gets too hot, repeatedly and just dies. Some plug up, others just quit working. My cat was a cheapy purchased to pass a smog in Az 2 yrs ago.
Next, he provided a laundry list of things to do and he swears that it will pass. But, I am now concerned that there may be a real problem of some sort and I want to investigate that before going any further. It's probably just a dead cat and/or o2 sensor but I want to be sure.
The following are the test results. Texas uses PPM & % as measurements while other smog states use "grams per mile" or similar units of weight as a measure....

Also...test was run today at 220-230 degrees during the entire test.
1st test HC 676 low speed (standard 157)
HC 562 hi speed (standard 152)


Co% 2.20 hi speed (stand 0.97)
3.01 low (stand 0.88)


Co2% 13.6% hi
13.0% low
No Standard%

02% 0.0% hi speed
0.2% low speed

NOX ppm 355 hi (stand 1082) (way under acceptable) PASS
359 low (stand 1184) PASS

Dilution%>6 15.8hi
>6 16.0 low

**************************************************************

2nd test today after major tune up, TB, IAC and TPS set.

HC 489 hi (standard 152)
590 low (stand 157)


CO% 3.15 hi (stand .97)
2.17 low (stand .88)


CO2% 13.1% hi
13.5 low
O2% 0% hi
0.3% low
NOx ppm 353 hi (standard 1082) PASS
441 low (standard 1184)
dilution% >6 16.3 hi
>6 15.7 low speed

All injectors test ok, no blow-by in PCV vents...no visable smoke, no oil burning. MPG has been low-mid 20's on hiway at 2000 rpm.

 

[Schrade]

Too much gasoline. It's cooling the burn, and making the bad numbers.

You said starting fuel pressure is 36? It really needs to be 42 - 43. It NEEDS pressure to spray HARD, and atomize the fuel better. Since it holds that pressure for bleed-down, you can't put the rap on the injectors. Maybe an adjustable FPR? This for one, will allow better burn, but I don't know how much...

In the meantime:

Double the alcohol (same or less gas).
Advance timing 6 - 8 degrees.
Disconnect the fans.
Change oil to syn 20W - 50 (just for the test).

 

[toptechx6]

The IM 240 test you need to pass is one of the more difficult with a modified engine. If you have checked for codes and there are none stored the O2 sensor is probably working, but if you have a scan tool it would be a good idea to verify it is switching rich/lean. Cats can only function if the O2 sensor is working properly.
Testing for a clogged cat is fairly easy using a vacuum gauge, but that is probably not the case or you would notice a serious power loss. Cats can fail without clogging however and testing for function is more difficult, especially without a 5 gas analyzer. One method copied below can give some indication of operation and only requires an accurate digital temp gun.
Another option would be to have the car checked by someone who specializes in emission testing and repair, ask to make sure they have a gas analyzer, they should also display credentials indicating their techs have been trained for such diagnosis. While you may get lucky installing a new cat, sometimes taking it to a pro can be more cost effective, good luck.

 

[boomdriver]

Schrade,
I'll try the suggestions. It has a Adjustable FPR now, I just turned it down a bit. It was set at near 45 for the first test. It has fresh 15/50 mobile-1.

Reading your article on the cat testing really makes me suspecious of that thing....my exhaust is TOO cold. I can barely feel warm gases exiting the tips. Nowhere near hot. I have an infra red sensor.;...and I think I will get under the car running and see which side is hotter. I bet its even. I'm also going to pull a couple plugs to see what they look like.

I raised the eng op temp to stock spec, with fans on at near 230. Thats where it tested yesterday.
Thanks for the info. I have decided to get a full scan to get a better idea of whats going on inside.

Do you think the EGR could be part of this? with the low Nox numbers, it could be leaking, but it seems like the engine would really cough and choke if that were the case...

 

[Schrade]

Schrade,
I'll try the suggestions. It has a Adjustable FPR now, I just turned it down a bit. It was set at near 45 for the first test. It has fresh 15/50 mobile-1.

Reading your article on the cat testing really makes me suspecious of that thing....my exhaust is TOO cold. I can barely feel warm gases exiting the tips. Nowhere near hot. I have an infra red sensor.;...and I think I will get under the car running and see which side is hotter. I bet its even. I'm also going to pull a couple plugs to see what they look like.

I raised the eng op temp to stock spec, with fans on at near 230. Thats where it tested yesterday.
Thanks for the info. I have decided to get a full scan to get a better idea of whats going on inside.

Do you think the EGR could be part of this? with the low Nox numbers, it could be leaking, but it seems like the engine would really cough and choke if that were the case...

I don't think turning down the FP is the right thing to do. It SEEMS that you would get less gas with less pressure, but I don't think this is the case. What IS for sure if you do that is that the fuel will dribble out, instead of spraying hard.

If everything else is working properly [stable], then the ECM will accordingly REDUCE the injector pulsewidth. Not necessarily that it is correct as is, but it's adjusting the way it's supposed to.

Lower the FP, and the fuel will atomize WORSE, then pass through less-well burned, cooler, HC's high, O2 high (lean), all of which you show, and the computer will ADD fuel/pulsewidth time to the lean (or what it THINKS is lean) burn, making it worse.

Increase the FP for better atomization, and THEN the computer will DECREASE pulsewidth to reduce fuel.

The computer code is written to adjust air/fuel mix, so that as LITTLE fuel as possible is used for a theoretical perfect combustion/decomposition of each molecule:

This is propane - same as octane; just has less carbons and hydrogens. What's important is NO C3H8 (or even ANY HC's) on the right side of the equation (unburned).

 

[boomdriver]

well, ok. I have read that before and understand spray patterns from injectors..

What I did learn from poking around this morning is that i DO have a "dirty" cylinder. It seems that all are burning clean, white plugs with the slightest bit of tan on the insulator except for #7. It is much darker, brown in color.
Now, the fun begins with why.

I am going to get it on an engine scanner and see if that will indicate an issue with #7. From there I can see if its fuel or oil. Its very possible to have an injector that it damaged and dumping too much fuel with each pulse. The solenoid is fine, but that does not mean the nozzel is perfect.
I would think that if it were burning oil in that cylinder from a broken ring or whatever, that I'd have some blow-by, which I do not.
In the meantime I will dial up the FP to over 40 and see about a good scan. Thats gonna happen pretty quick because I won't be able to sleep thinking that I have to pull this motor and rebuild over 1 broken ring.....I can live with pulling the fuel rails and injectors.

 

[Rex S]

You need to see what the O2 sensor is seeing. If the values are changing very slowly and only by a couple points it needs replaced. A Random Tech cat will be a good bet too.

 

[boomdriver]

Yep...
I have a new o2 sensor if the old one is in bad shape.

I have been timing the fuel pressure drop to make certain of that...

Set to 44-45 lbs.
Holds that for 5 min then drops about 1lb per hr.
After 15 minutes the pressure is down to about 30.
After 1/2 hr it still has over 20 lbs.
At 1.5 hrs it has 18 lbs fuel pressure remaining.

So, I think the injectors are solid.
The dirty #7 cylinder worries me alot. I think a compression test is next tomorrow.

 

[roger longman]

Hi boom, I'm no help with the technical advice but for comparison,you say Texas is way hard on the smog test. Here in L.A. mine tested,for HC, 74 high against 86. 112 low against 112. I thought I had problems !......Roger.

 

[boomdriver]

Roger, I'm not sure which standard of measure they use in Ca....some use ppm, others use grams per mile, so forth. I have had this car smogged in Orange County several times then twice in Az. The Tex test seems harsh because there is no way to confirm what their equipment reads. The 96 yr and newer simply get away with a printed report off the cars own diagnostic system, while I have to run the dyno.

 

[toptechx6]

Roger, I'm not sure which standard of measure they use in Ca....some use ppm, others use grams per mile, so forth. I have had this car smogged in Orange County several times then twice in Az. The Tex test seems harsh because there is no way to confirm what their equipment reads. The 96 yr and newer simply get away with a printed report off the cars own diagnostic system, while I have to run the dyno.

You are correct, all gas analyzers available to technicians measure in PPM which is percentage and there is no formula for conversion to GPM which is a measurement by weight.
Weight of emissions is proportional to engine size so if you modify your 350 by stroking for example the tune will need to be cleaner than the GM original to achieve the same emission level.
96 and newer cars are OBDII which was designed to be an on board emission monitoring system, that is the reason for the downstream O2 sensors which monitor catalyst efficiency.

 

[geekinavette]

Dang that thing is awfully rich. I would think that if its THAT rich, and the O2 sensor was working properly, that it would be throwing a rich code.

And unless there have been some engine modifications...I don't agree with doing all of these adjustments (alcohol, timing....etc, and disconnecting the fans? :confused ), as it should pass in stock form (assuming it IS in stock form)...something is just not right.

I have seen this happen when there was an exhaust leak upstream from the O2 sensor (stock C4 headers are notorious for cracking). Through a "scavenging" effect the exhaust can actually take in air (at the leak point) and fool the O2 sensor into thinking the A/F mixture is lean, of course as a result the ECM dumps too much fuel and you end up with a rich exhaust...yet the ECM "thinks" it is ok.

 

[boomdriver]

Geek,
Thats basically the problem, it has LOTS of engine mods. From boring to porting to the edlebrock throttlebody to proms, name it, its been upgraded or altered....Even the big edlebrock TB was polished inside. I left the bottom end pretty much stock except for the balancing of the rotating assy.

I'm having to un-do things until it gets to an acceptable level and returning temporarily to a semi-stock form. It still runs great, But I can tell that throttle response is more sluggish, and the power-band is a bit flatter with the removal of some mods.

Yeah, its running rich somehow, somewhere. I have managed to isloate the #7 cyl as "dirty" and suspect it as part of the problem. Oil or fuel is the big question.:confused.
I now suspect the fuel after compression testing cylinders today and finding them ALL within 2 lbs of each other. #5 & 7 were exactly the same. #1 was maybe a lb or 2 lower. Pressure calculations show 10.2:1...almost exactly what it was estimated to be when built.

As far as the #7 cyl is concerned, That injector might be damaged or slow to close when pulsed. Something is getting that spark-plug dirty and it ain't oil from rings. A valve seal maybe, but thats a long shot since no others are leaking.

Yesterdays fuel pressure leak down test had good results with 18 lbs present over 2 hrs after charging system to over 40 and allowing it to bleed down on its own. Started at over 40, lost much less than 1 lb per minute until it got down to 20...then sat there forever. Still had fuel spray several hrs later when pulling the test gauge off. Still, something is not right in #7....

If the #7 injector nozzle is damaged that would explain the brown spark plug. Again, all 8 inj solenoids check out at 16.9 or 17 ohm.

Today I made a BUNCH of calls looking for someone that had the correct equipment to run a full dianostic on the OBD-1 and engine. No such luck. I'll talk to a couple vette shops tomorrow about that. Everyone else has gone to the simple OBD-2 scan equipment around here and traded in their scopes and gas analyzers yrs ago when the state initiated smog inspections. Lots of places can do a scan, but all they're doing is running the DTC's. If there are none stored, they can;t tell me anymore than my flash codes will.

Next step is to test the CAT for function. I almost bought a temp scanner that would handle 700 degrees...but for the money and the fact that I'd use it once and forget that I owned it, I decided to pass. I'll pay someone else to check inlet vs outlet temps on the cat to see if its dead or not. It was a cheap one, and more than one good wrench operator tells me that cats CAN die without plugging.

My nOX levels were very low on both test. If memory serves me, that indicates low combustion temps, does it not? If that is the case, could a mild EGR leak be cooling the combustion too much to get a good clean burn? 7 of 8 cyls have plugs that read perfect, so I'm not leaning toward an EGR issue.

I guess I can pull the plenum and clean the EGR ports too. Check the EGR valve and being sure. Its not like I have to drive to Brazil on Thursday...I'm still trying to comprehend "retirement" and actually having the time to do things. I still feel pressured on weekends to get it done before Monday....old habit.

I also disconnected the o2 sensor and ran it intentionally to see what happened....the ECM did exactly what it should, doing nothing until things were hot enough, and run for the required 2 minutes then it set the code. I'll still replace the o2 sensor as soon as I can get it on a lift where the 4 ft cheater can be applied.
I am curious about the AIR management valves...the AIR sys muffler seems to make a lot of noise when the engine is at 210+ degrees. That tells me that the air is being wasted and not injected into the CAT or manifold fittings. I need to re-read that chaptor on the valves and testing.

Anyone have any thoughts on this latest info? If I can find a real scan I'll get it and post the results, but like I was saying, most places simply don't have the software or the equip to look at an 80's model anything. The vette shops all have a waiting line, but it might come down to having to drop it off for a couple days in order to get some answers.

 

[Schrade]

Geek,
Thats basically the problem, it has LOTS of engine mods.

This is why I'm against modded engines, unless it's done on NEW engines, with a PROFESSIONALLY written TUNED ECM chip. Little late now, I guess, but the ONLY thing to do to get it TRULY right, is restore OEM hardware, THEN check with a scan.

And unless there have been some engine modifications...I don't agree with doing all of these adjustments (alcohol, timing....etc, and disconnecting the fans? :confused ), as it should pass in stock form (assuming it IS in stock form)...something is just not right.

The reason I offered those tips is simple (short of cleaning up the burn through proper tune, which ain't happenin' so far):

Alcohol burns hotter. He's burning cool, for whatever reason - too much gasoline. ETHANOL, which is what he needs to load, not METHanol, combusts into CO2 and water.

Advancing the timing heats the burn. Alcohol allows higher squeeze, but since that can't be done for the inspection, he needs to advance timing.

Disconnecting the fans will allow the motor to run up above 228 without the fan cooling it back down to 218.

Running the test with 20W - 50 syn oil will offer extra protection while it runs hotter during the inspection. AND, if cylinder #7 is taking oil from a bad ring, then a little LESS oil is going to go through the exhaust with heavier viscosity.

If he does what I say, his numbers WILL drop MORE, like they did the second scan.

You didn't say WHY you don't agree... :confused

scanner

 

[navy2kcoupe]

Would it be possible to swap the injector from cylinder #7 with one from the other side of the engine? See if the problem moves to that cylinder?
Andy

 

[c4c5specialist]

HI there,

I think you need to get back to square one.

Your readings do NOT indicate any issue with EGR or carbon buildup, so IGNORE THAT!

Second, your readings are NOT that far off the mark.

What KIND of o2 sensor did you run ????? ACDelco or something else ???

Is the cat original ??

What are your millivolt readings once warm ?????

If you can get data, what are your integrator and block learn specs ??/ They should be near 128.

Honestly, it all depends on what you have on these readings.

TEST of a catalyst requires readings before and AFTER the cat. HC, CO, CO2, NOX

If you cant do that, dont waste your time.

Get those readings and we can isolate your issue.

Allthebest, c4c5

 

[geekinavette]

Ahhhh this is a heavily modified engine...in that case never mind!