Emissions testing query

[Vuarra]

I just took my 87 Regal with 305ci SBC engine to be e-tested, and got a pass on just about everything except for CO% at idle, (limit 1.50%, reading 2.19%). Strange thing is that at 25 mph, the limit is 0.56% and I scored 0.01%, again for carbon monoxide. HC concentrations for both idle and 25mph are at about 75 - 80 % of the limit and NOx is at about 55% of the limit. I'm pretty sure the cat is not to blame for this one.

I'll be replacing the air filter, cleaning the carb, and changing the oil (more green gummi bears for my collection!). Is there anything else I should be looking at?

 

[Ken42]

Excessive CO is caused by incomplete combustion and is generally a fault of timing or ignition system. Check your plugs wires cap rotor and timing.
Also make sure your oxygen sensor is good. When you do the test be sure the beast is HOT do not shut it off before the test.

Ken

 

[Vuarra]

There is no O2 sensor in this car, and the cap and rotor are new (within 5000 miles).

While I agree with you, it doesn't make sense as the driving part of the test shows nearly no carbon monoxide, almost 0%

Thanks for the input

 

[Vuarra]

Bah!!!

I sprayed the snot out of the carb, changed the air filter, breather and PCV valve.

Apparently, none of the above was needed, as the tests came out worse. I failed worse than before I did the work.

Any ideas?

 

[brianl703]

Are you 100% sure it doesn't have an oxygen sensor? I would have thought by 1987 GM would have put their "computer command control" feedback carburetor stuff on all of the models with the 305..

 

[tom slick]

what were your co2 and o2 numbers? they are also indicators if what your problem is.

 

[T-Keith]

Did you swap in the 305? Regals never came with a SBC.

-T

 

[kevm14]

Right, if it's a V8, it would be the 307. But even so, it should have an O2 sensor for the q-jet to control itself.

 

[brianl703]

That O2 sensor is a most likely a single-wire unheated sensor. If it is, it might improve emissions at idle to replace it with a heated sensor (requires 12V and ground connections).

 

[DJStillman]

quote:

---

Originally posted by brianl703:
That O2 sensor is a most likely a single-wire unheated sensor. If it is, it might improve emissions at idle to replace it with a heated sensor (requires 12V and ground connections).

---

Sorry to hijack this thread, but can we hear more about this procedure? Should I maybe start a new thread?

 

[dkcase]

quote:

---

Originally posted by brianl703:
it might improve emissions at idle to replace it with a heated sensor (requires 12V and ground connections).

---

This would only make a difference at start-up, no ? Until the sensor gets hot ?

 

[brianl703]

Apparently, at idle the non-heated O2 sensor can cool off and stop working, which causes idle emissions to increase. (This is why they should rev the engine up to make sure the O2 sensor is good and warm, and THEN do the idle emissions test)

This is in addition to the problem of the non-heated O2 sensor taking longer to get hot enough to start working from a cold start.

To alleviate both problems, the heated O2 sensor was developed.

A 3-wire heated O2 sensor can replace a non-heated 1-wire O2 sensor if you connect the extra wires (two white wires) to a source of 12V and ground. The black wire connects where the single wire from the original O2 sensor did.

I would suggest connecting the heater directly to the battery through a relay whose coil is connected to a source of 12V that is hot when the key is in the ON position.

Using a relay is to avoid drawing any more current through the often already-strained ignition switch (although it is wired directly to the ignition switch on my '88 Mustang). The heater takes a couple of amps or so.

 

[Jimbo]

Timing was the culprit on my mom's 1987 Dodge. A little too much advance at idle will increase CO readings. BTW, it does have an O2 sensor and some kind of solenoid inside the carb.

 

[dkcase]

Brianl703:

Interesting. Thanks.
I'll print this out and save it.
Who knows when they'll have to tussle with the emissions inspection folks.
I know I've found it necessary to raise my voice in there before.

 

[ALS]

Try this link it should help you find the problem.
Emission causes

 

[Vuarra]

Thanks to all who have responded.

Remember that I'm in Canada, and the emissions profile up here allowed a stock 305 SBC. While I might do a swap later on (I'm thinking at supercharged 3800, or something else a little funky), that's the standard engine.

I have NEVER seen anything that remotely resembles an O2 sensor on the exhaust pipe, from the manifolds back to the tail pipe. There is the possibility that it was somewhere hidden, as I do have a feedback Carb.

For now, I'm just going to park the thing in my driveway, and tear it down next spring.

Again, thanx to all who replied.

Here is the report that the province considers:

ASM2525 Idle
Limit Reading Limit Reading
HC 101 101 300 296
CO 0.56 0.02 1.5 3.45
NO 1091 817 N/A N/A
RPM Bypass RPM BYPASS
Dilution 14.4 Dilution 16.2

Figure in BOLD is a fail.

They don't record what the O2 readings were

[ December 13, 2004, 12:54 AM: Message edited by: Vuarra ]