Another 1991 Fails CA emissions... Help!

[Shinto]

I've read all the posts about failing emissions, but haven't come across my particular problem (close, but not quite).

I've had the car since it was about 4 years old / 4,000 miles and have since added Borla exhaust and an X-pipe. The car is otherwise unmodified and completely stock. It has always passed smog with flying colors in the past and the last test was only about 8-10k miles ago.

Since the last test: I added the X-pipe and changed the alternator (by removing the throttle body, not the plenum). I just changed the oil to Mobil 1 High mileage about 400 miles ago to protect the cams. The car has 39,800 miles.

I had to go to a test only station since the state has selected me as a "high emitter profile" and here in Sacramento we have to do emissions testing under load on a dyno at 15 and 25 mph.

I filled the tank with 91 octane (I always run super) and drove it on the freeway prior to the test to warm it up and blow out the carbon. The coolant temp was around 220 and the car was audibly pinging during the test.

The failure is in NOx emissions at 15 mph (and nearly failed at 25 mph). All other measurements were passing and quite low.

15 mph / 1298 rpm
CO2: 14.7 (no limit)
O2: 0.2 (no limit)
HC: 14 (limit 112)
CO: 0.01 (limit 0.72)
NO: 1135 (limit 778) ***

25 mph / 2106 rpm
CO2: 14.7 (no limit)
O2: 0.2 (no limit)
HC: 13 (limit 86)
CO: 0.01 (limit 0.60)
NO: 527 (limit 717)

What has failed? The tech suggested maybe carbon deposits (but I blow it out quite frequently and did just prior to the test) and the coolant temperature being high.

Man I hate California! I already can't drive my '78 Trans Am with 48k due to failing as a gross polluter an now this @#$%#$%. Wish I could just bribe someone...

[rhipsher]

Wish I could just bribe someone...

Shhhhh! Don't tell anybody you heard it from me but You can bribe somebody. Just be ready with a 24 pack of bear on a friday night an hour before they quit for the night.

[Shinto]

Shhhhh! Don't tell anybody you heard it from me but You can bribe somebody. Just be ready with a 24 pack of bear on a friday night an hour before they quit for the night.

Unfortunately, this ridiculous state sends out undercover investigators (including little old ladies) to try to get smog techs (and fine them heavily and revoke their licenses). If you don't know them personally, they pretty much jump at every shadow. It's far easier to buy said 24 pack of beer if you're under age.

[Jeffvette]

Possibility of running lean with hot spots in the combustion process.

[tccrab]

Since a '91 doesn't have an EGR system, my next guess would be fouled Cats.
Bummer.
Be prepared to spend some time at the referee station.

TomC
"Crabs"

[Kb7tif]

Sorry to hear this.:-x
Cant a special propose chip be burned for this?

[-=Jeff=-]

if you need OEM Manifolds an cats assuming you determine yours are bad I have mine off my 90 I would sell cheap

[Sgreg]

Possibility of running lean with hot spots in the combustion process.

I had some luck with colder iridium plugs. Any rate if the plugs have more than 5-7000 miles I would change them.

[gbrtng]

The audible pinging is a clue - it's running lean with advanced timing. Maybe a failing injector or knock sensor. What gear do they run the 15 and 25 mph in?

Also, has CA lowered the NOx limit recently?

[Shinto]

Since a '91 doesn't have an EGR system, my next guess would be fouled Cats.
Bummer.
Be prepared to spend some time at the referee station.

TomC
"Crabs"

I have no real reason to believe fouled cats, since that would cause the HC and CO to go up dramatically as well.

[tccrab]

There is a member here that used to own a SMOG shop in Sacto.
He'd be the one to nail this down.
I'll dig him up if he's still around.

TomC
"Crabs"

[Shinto]

The audible pinging is a clue - it's running lean with advanced timing. Maybe a failing injector or knock sensor. What gear do they run the 15 and 25 mph in?

I'm not sure what gear, as the test is about as hands off as it gets. I'm not allowed in the service area. That's why I gave the listed rpm (I'd guess 2nd).

Also, has CA lowered the NOx limit recently?

It's against federal law for them to change the limits for the model year car to be lower than what was originally approved, but it wouldn't surprise me if they did. They keep making the testing increasingly hard to pass and thinking up new ways to fail cars. They actually pressure tested the GAS TANK in the '78 Trans Am and failed it on that (as well as other tests).

This last go round the smog machine actually gave NO feedback to the operator in terms of emissions -- only rpms and speed. We didn't know it failed until the test was over and it printed out.

I also see more and more data printed out every time I have a test done, regardless of model year. (Ask me what I REALLY think of this in an uncensored forum... Starting to remind me of a certain country in Europe in the late 1930's...)

How do I test the knock censor and injectors?

[tccrab]

Found this in the archives:
http://www.zr1netregistry.com/forum/showthread.php?t=131

I'm trying to remember the guys name who owned the SMOG shop down in Sac, "BennyC" keeps coming to mind.
I've checked the archives here and I don't find him so it must have been on that "other site" long before I got the boot.


TomC
"Crabs"

[jonszr1]

boy sure makes me glad that our county doesnt have to test unless we sell the car .you might think about finding a freind in sonora that would let you register the car there

[Paul Workman]

The audible pinging is a clue - it's running lean with advanced timing. Maybe a failing injector or knock sensor.

I agree w/ gbrtng that the pinging is the clue that it is running lean, and or the spark is too advanced(?), especially if it is pinging on 91 octane. Marc H can provide you with a chip that will bring the fans on while the temps are a little cooler. Cooler would help N0x, but too cool and HC will creep up - it is a balancing act. 10º cooler (both fans coming on at around 206-210) might do it for ya.

Anywayz...I would do a dynamic scan/data logging to see what other clues might pop up before I started changing this and that in hopes the problem goes away. BTDT.

P.

[gbrtng]

I asked about the NOx limit because Hib was complaining about CA lowering it several years ago - and what to do to help the 94-95 cars with EGRs. And it would be to your advantage to scan the system before throwing parts at it.

[Dynomite]

I'm not sure what gear, as the test is about as hands off as it gets. I'm not allowed in the service area. That's why I gave the listed rpm (I'd guess 2nd).

Holy smoke :rolleyes: WOW....Now I know why I am registered in South Dakota :thumbsup:

[tomtom72]

:o I'm not trying to be a wise guy. I live in NYS, in the NYC/Metro-suburban area and we have strict smog regs like CA. We even do this roller loop test at 15 & 25 mph.

Anyway, two inspections ago the place called me up to give me the heads up that my car wouldn't pass the NOx test. We don't have "state run smog inspection stations". We have auto repair shops do the testing. I went over and found that I had left the power key in the "Full Power" position. :redface:

Just a shot in the dark!

[RKC]

I have a 1990 that gave me fits getting pass smog. Here are my results from my first failure.

15 mph / 2294 rpm
CO2: 14.7 (no limit)
O2: 0.2 (no limit)
HC: 51 (limit 110)
CO: 0.01 (limit 0.71)
NO: 868 (limit 772) ***

25 mph / 2450 rpm
CO2: 14.7 (no limit)
O2: 0.2 (no limit)
HC: 41 (limit 85)
CO: 0.01 (limit 0.59)
NO: 987 (limit 711)

After I passed:


15 mph / 2190 rpm
CO2: 14.7 (no limit)
O2: 0.2 (no limit)
HC: 109 (limit 110)
CO: 0.10 (limit 0.71)
NO: 611 (limit 772) ***

25 mph / 2440 rpm
CO2: 14.7 (no limit)
O2: 0.2 (no limit)
HC: 52 (limit 85)
CO: 0.01 (limit 0.59)
NO: 667 (limit 711)

I passed the test after using fuel injector cleaner, changed the oil, replaced the spark plugs, and cleaned the air filter. I used Chevron gas. My engine has 45,000 miles and blows a little oil on startup.

I did have new bullet cats on SW headers. The cats may have helped ,but they didn't help it pass the first time. I also have 4.10 gears in rear.

One major difference I noticed is the RPM's at 15 mph. In your test, you're barely off idle at that low RPM. Nearly 900 fewer than mine. About 350 RPM's less at 25 MPH.

Also, I'm not sure of the reasons, but in passing the NO portion of the test, I very nearly failed the HC portion. I tested on a summer day. The technician had the car running for nearly 20 minutes before and during the test. With the aftermarket radiator it ran very hot at idle. I subsequently swapped it for a stock radiator and dramatically improved the idle temperature. My point being, the engine coolant temperature had to be extremely high during the test.

Also on the first test failure, they failed me on my gas cap. I replaced it with a new one. Don't know if that would cause any actual exhaust emissions change, but on a newer OBD II vehicle of mine it set an error code that I couldn't solve until I finally replaced the gas cap. It immediately cleared the problem and never reset.

[RKC]

I'm sorry, but I failed to mention that I failed the first test with an aftermarket PROM. I managed to buy the last stock PROM for a 1990 in the Chevrolet system. They shipped it all the way from Maine. I'm certain that must have played a large role in passing.

[RKC]

I have a 1990 that gave me fits getting pass smog. Here are my results from my first failure.

15 mph / 2294 rpm
CO2: 14.7 (no limit)
O2: 0.2 (no limit)
HC: 51 (limit 110)
CO: 0.01 (limit 0.71)
NO: 868 (limit 772) ***

25 mph / 2450 rpm
CO2: 14.7 (no limit)
O2: 0.2 (no limit)
HC: 41 (limit 85)
CO: 0.01 (limit 0.59)
NO: 987 (limit 711)

After I passed:


15 mph / 2190 rpm
CO2: 14.7 (no limit)
O2: 0.2 (no limit)
HC: 109 (limit 110)
CO: 0.10 (limit 0.71)
NO: 611 (limit 772) ***

25 mph / 2440 rpm
CO2: 14.7 (no limit)
O2: 0.2 (no limit)
HC: 52 (limit 85)
CO: 0.01 (limit 0.59)
NO: 667 (limit 711)

I passed the test after using fuel injector cleaner, changed the oil, replaced the spark plugs, and cleaned the air filter. I used Chevron gas. My engine has 45,000 miles and blows a little oil on startup.

I did have new bullet cats on SW headers. The cats may have helped ,but they didn't help it pass the first time. I also have 4.10 gears in rear.

One major difference I noticed is the RPM's at 15 mph. In your test, you're barely off idle at that low RPM. Nearly 900 fewer than mine. About 350 RPM's less at 25 MPH.

Also, I'm not sure of the reasons, but in passing the NO portion of the test, I very nearly failed the HC portion. I tested on a summer day. The technician had the car running for nearly 20 minutes before and during the test. With the aftermarket radiator it ran very hot at idle. I subsequently swapped it for a stock radiator and dramatically improved the idle temperature. My point being, the engine coolant temperature had to be extremely high during the test.

Also on the first test failure, they failed me on my gas cap. I replaced it with a new one. Don't know if that would cause any actual exhaust emissions change, but on a newer OBD II vehicle of mine it set an error code that I couldn't solve until I finally replaced the gas cap. It immediately cleared the problem and never reset.

[Z51JEFF]

Not to hijack your thread here but you have a law maker,Dave Jones that represents Sac THAT NEEDS TO GO.This moron has proposed a bill several times making smog tests annual.Id vote the guy out of office but Im in the Bay Area.

[Dynomite]

Not to hijack your thread here but you have a law maker,Dave Jones that represents Sac THAT NEEDS TO GO.This moron has proposed a bill several times making smog tests annual.Id vote the guy out of office but Im in the Bay Area.

If you are in Bay area......work on getting Nancy Pelosi out of office :D

[Z51JEFF]

If you are in Bay area......work on getting Nancy Pelosi out of office :D

Come November 2010 Ill do my best to get them ALL out.

[Shinto]

Not to hijack your thread here but you have a law maker,Dave Jones that represents Sac THAT NEEDS TO GO.This moron has proposed a bill several times making smog tests annual.Id vote the guy out of office but Im in the Bay Area.

What a @#$&. Unfortunately, I live outside his district so I can't do much to oust him. To me, public enemy no. 1, Sally Leiber from Mountainview has already been term limited out of office. She's the one to thank for rolling exemptions going away.

I don't think Pelosi is going anywhere. Her district (SF) is extrememly liberal and she now has real power (much like her cohort Diane Feinstein).

-----------------

I have half a mind to run a tankfull of injector cleaner, run it hard to really blow out the carbon, and smog it with the engine cold at a different shop instead of using my free retest. (Another $50 down the rathole.) HC and CO should go up, but I've got lots of room to play with there. Colder operating temperatures should get rid of the pinging and lower the NOx. Aside from a partial injector clog or failure, I don't know why it would be running lean. Bad MAF or O2 sensor? I'd imagine that would trigger a SEL code... (which is now an instant fail if you have any codes in memory or the light on.)

I don't think the power key was turned on, as I shut the car down when I got there and they restarted it to pull it into the bay, but I'll pull it out to be sure next time. I may also look into the iridium plugs. Definitely Chevron gas. Any other suggestions?

[tccrab]

Take it to Folsom Smog on the corner of Blue Ravine and Prairie City Road.
Ask for Bob Nailor.
Tell him I sent you.
Bob used to have a '91 ZR1 and I believe he still may have an extra PROM or two for you to try out.

I PM'd Benny C over at the CF, he used to own a smog shop over off of Arden in Sac. He has a '94 ZR1, haven't heard from him yet, tho.

Tom

[zrmynatt]

Have your A/C turned on when they test that will turn the cooling on and cool the engine down, that or move to Texas

[SillyB]

if you need OEM Manifolds an cats assuming you determine yours are bad I have mine off my 90 I would sell cheap

How cheap is cheap? I have a failing cat on the driver's side in my 1990. I'm ok for now, but I'll be back at the smog Nazi's inspection soon enough and will be needing them.

[-=Jeff=-]

How cheap is cheap? I have a failing cat on the driver's side in my 1990. I'm ok for now, but I'll be back at the smog Nazi's inspection soon enough and will be needing them.

Sold them.. sorry

[cuisinartvette]

Always have the power key off when smogging out here.
On the nox dont know what the problem is there.