1991 ZR1 Failed Emissions

[Jason 91]

Gbrtng:

The degradation is the main reason I initially thought it was the OE injectors failing.

The gasoline was fresh. Before I took it in for the test, I drained the tank by driving it back and forth between Denver and my CO Springs office which is about 55 miles each way. I refilled it shortly before going to take the test. Also, the car was up to normal operating temperature. The frustrating thing, and I’m not sure if this made a difference, was having to idle for about 45 minutes while waiting in line. This caused the fans to come on a couple of times.

Goldcylon:

Where did you get the 1991 exhaust manifold/catalytic converter from? Did you get it from another member? I just had a member reach out to me. Thanks Greg!

Tomtom72:

The injectors are OE and with the ethanol here, I expect to be replacing them soon either way. Is there specific scan data we should look at that demonstrates the injectors are going bad or is it you need to see a continuing rise/decline in specific results?

I’m not going to let them fail me again for the air injection system after I’ve confirmed that all original equipment is in good working order.

Thanks for the link. I’m still learning (you seem like more of a mechanic than me ) and information is always helpful.

All:

Feel free to comment on any of these above responses. I’m trying to make sure that I respond to all questions asked because I really appreciate you guys taking the time to help me.

I will verify that it is in fact the cat that is bad before anything gets cut, but I have a couple of questions assuming that it is.

Assuming the exhaust manifold/catalytic converter needs to be replaced, how much R & R labor hours am I looking at for each? I’ve read the FSM (and Chilton’s for what it’s worth), but I have little practical experience so I’m having trouble figuring it out and am probably oversimplifying it.

Is a universal cat even an option as a last resort (I see some for sale)?

Are there any header options that I could still pass emissions with assuming everything else is in good working order?

Again, I appreciate all of the help you guys are giving me.

Thanks,

Jason

[Aurora40]

Just FWIW, here is the difference new injectors made on mine, with all within fairly acceptable ohm readings. My injectors leaked, if you pulled the fuel rail you could watch the drops form on them. I could also smell gas if I cracked the throttle body an hour or more after shutting the car down.

Anyway, VA doesn't do GPM. But here is what happened:

Before:
HC 30 PPM @ 15mph / 76 PPM @ 25mph
CO .06% @ 15mph / .08% @ 25mph

After:
HC 13 PPM @ 15mph / 13 PPM @ 25mph
CO .05% @ 15mph / .02% @ 25mph

The other change along with the injectors was a ported intake and a Haibeck chip. Though I believe the injectors are the reason for the emissions cleanup.

On the topic of cats, I believe the '93+ two piece manifold/cat can be put on the early cars. And it should fit up to the exhaust. I believe they are still available new from GM. You also could buy the '90-92 style ones used. Or you could just make the jump to headers and cats. Or possibly try to track down a set of Callaway (Lingenfelter sold them too I believe) header/cats if you want some gain from a stock type manifold.

I don't believe you could very attractively replace it with a universal cat? You'd presumably have to gut out the factory cat, then cut/weld in a universal one somewhere downstream.

Just for grins after seeing you post GPM, the testing in Colorado uses the IM 240 testing standards. A clean running ZR-1 will have problems going through the test as it is so dependant on the tester being able to drive the car correctly.

We used to have the 240 test in Oregon and they phased it out as it was to expensive and also was not generating the results they wanted.

Are you failing on the accel or decel portion of the test?

[gbrtng]

Mine made the fast pass (90 seconds) IM240 test in IL in 2003 after lots of expense. New O2 sensors, and a fresh set of cats with headers didn't make much difference to the HC numbers. Finally Haibeck diagnosed a leaking vapor canister - which is in the right rear fender right where the IM240 exhaust hose picks the exhaust - and a replacement cannister cleaned her up.
This is on s 44,000 mile car with original injectors. This does not compare with Jason's problem because mine was OK on all but the HC numbers. Point being that each vehicle is different with its specific problems. At least in IL you have the option to declare a vehicle a "race car" making it exempt from testing. Maybe CO has some trick exemption you can use ...

[Bill]

Jason, If you need some hands on wrenching? I met these guys last June during CruiseFest. I lost a primary fuel pump, They got me running in short order and a reasonable price. I don't know if they do smog, but they know their stuff.
Good folks and close to you
http://www.corvettecenterusa.com/

[Zr1 Destroyer]

Hit me up......i have an emisions only flow master sytem that i use for my Zr1.


I removed the center muffler for a cat converter and the Y pipe just after the factory headers has one cat welded in place for a total of three cats just on the flow master system!

Also if you try it again flog the living hell out of it for about 20 minutes to blow all that crap out and to heat the hell out of the factory cats! Is your air pump working?

Ry in thornton, co.

[Zr1 Destroyer]

Originally Posted by Jason 91

Gbrtng:

The degradation is the main reason I initially thought it was the OE injectors failing.

The gasoline was fresh. Before I took it in for the test, I drained the tank by driving it back and forth between Denver and my CO Springs office which is about 55 miles each way. I refilled it shortly before going to take the test. Also, the car was up to normal operating temperature. The frustrating thing, and I’m not sure if this made a difference, was having to idle for about 45 minutes while waiting in line. This caused the fans to come on a couple of times.

Goldcylon:

Where did you get the 1991 exhaust manifold/catalytic converter from? Did you get it from another member? I just had a member reach out to me. Thanks Greg!

Tomtom72:

The injectors are OE and with the ethanol here, I expect to be replacing them soon either way. Is there specific scan data we should look at that demonstrates the injectors are going bad or is it you need to see a continuing rise/decline in specific results?

I’m not going to let them fail me again for the air injection system after I’ve confirmed that all original equipment is in good working order.

Thanks for the link. I’m still learning (you seem like more of a mechanic than me ) and information is always helpful.

All:

Feel free to comment on any of these above responses. I’m trying to make sure that I respond to all questions asked because I really appreciate you guys taking the time to help me.

I will verify that it is in fact the cat that is bad before anything gets cut, but I have a couple of questions assuming that it is.

Assuming the exhaust manifold/catalytic converter needs to be replaced, how much R & R labor hours am I looking at for each? I’ve read the FSM (and Chilton’s for what it’s worth), but I have little practical experience so I’m having trouble figuring it out and am probably oversimplifying it.

Is a universal cat even an option as a last resort (I see some for sale)?

Are there any header options that I could still pass emissions with assuming everything else is in good working order?

Again, I appreciate all of the help you guys are giving me.

Thanks,

Jason

Do you have a scan tool? Also have you changed the o2 sensors lately?

[Jason 91]

Aurora40:

New injectors are in my near if not immediate future. Thanks for the answer on the 93 + MY setup.

Jeffvette:

I gave the graph to the guy at the shop, but from what I recall, I was failing consistently based on my interpretation of the graph.
The state acknowledges that there is some driver dependency on the dyno and I will fight them if I can at least get close. It’s frustrating that it’s always going to be close though.

Gbrtng:

There are some exemptions that I could exercise, but I really want to get the car in good working order. It drove well to me so this is a little bit of a surprise. It would be nice to simply declare it a “race car” and get my current registration though.

Bill:

Thanks for the tip. I believe that I spoke to those guys one time before. I saw their site on a drive I was making and they gave me a pretty reasonable quote on replacing the weather stripping.

ZR1 Destroyer:

I appreciate the offer.
I live in Washington Park so I’m not to far away from you. So essentially you bolt this item on and it cleans up the exhaust for the test?
The air pump is functioning appropriately, but the O2 sensors are original and probably part of the upstream problem because I’ve had no trouble codes. I do not have a scan tool, but I need to get one because they are a necessity.

Thanks,

Jason

[Zr1 Destroyer]

ZR1 Destroyer:

I appreciate the offer.
I live in Washington Park so I’m not to far away from you. So essentially you bolt this item on and it cleans up the exhaust for the test?
The air pump is functioning appropriately, but the O2 sensors are original and probably part of the upstream problem because I’ve had no trouble codes. I do not have a scan tool, but I need to get one because they are a necessity.

Thanks,

Jason
[/quote]The emisions only system i have just ads a few more cats in the mix is all. I used for my old 368 that had a more then hard time passing the colorado e test.

If you ever want to pop your plenum off for any reason or just need help in general......also have a scanner that works nicely.

Ry

[WB9MCW]

"At least in IL you have the option to declare a vehicle a "race car" making it exempt from testing."


The big news in IL is now only 96 and up have to be tested so all ZR-1's get off the hook now!!!!