Interesting smog check puzzle--changing readings

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Joined
Aug 7, 2004
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Location
San Diego, CA
So, I got a smog test, and failed (1983 FJ60). Then I got another pre-test, and failed wildly differently. What happened?

The first test was

RPM: 1559 at 15mph, 2452 at 25 mph
%CO2: 13.6 at 15 mph, 14.0 at 25 mph
%O2: 0.6 at 15mph, 1.2 at 25 mph
HC: 41 PPM at 15 mph (max 189, ave 47), 13 PPM at 25 mph(max 113, ave 36)
CO%: 1.41 at 15mph (max 1.33, ave 0.18), 0.07 at 25mph (max 1.13, ave 0.14)
NO: 257 PPM at 15mph (max 1448, ave 546), 628 PPM at 25 mph (max 1308, ave 466)

So CO was high, running rich, right? So I top off the oil (it was low), top off the radiator (it was low), changed the air filter (I've seen worse but it was dirty), sprayed some carb cleaner in the carb, and ran some seafoam through the carb. I also did some air injection checks which looked good. Oh, and four cans of iso-heet type of product.

I go back to another guy, and he listens to what I did, and he didn't want to waste my money testing me after listening to what I did. So he ran a quick pre test, and at 25 mph I had the following:

HC: 16
CO: .06
NO: 2300

So, my CO went way down (to near what the 15mph CO was before) and my HC went way up into failure range. What gives? The smog check guy seemed to think I needed a catalytic converter, which may be. But it's really weird what happened between the tests.

And thanks to this guy for the help--I probably dodged a gross polluter there. If anyone needs a San Diego recommendation for smog testing, shoot me a PM.

My last test failure was high HC, and I fixed it with some combo of oil (if that helps), air filter, plugs, and an air injection check valve that was a bit plugged. This car is driven maybe 3000 miles a year; not much at all.
 
You gave us important facts but not all the facts.

It is really helpful to know the O2 and CO2 readings as well, for determining the combustion conversion and air injection performance (which looks suspect).

Hi NOx readings indicate hot combustion temperatures: so hot the fuel actually ignites under pressure before the spark plugs fire.

General sources of excessive NOx gases include:

Improper (advanced) timing,
Lean mixtures (vacuum leaks, low carb bowl levels, carb problems)
Non-functioning EGR system
Non functioning 3 way converter

Given the history you relate, I recommend looking at the vacuum hose routing, to see if there is a damaged vacuum hose connection causing advanced timing or an air leak.

Also look to see if the fuel level in the carb bowl is in proper range.

Do the step by step fault tree (from the FSM) on the EGR system to make sure it is operating properly and the passages are clear.

I doubt the CAT is your problem. On a properly functioning motor, NOx gasses are usually a pass without a 3 way converter.

Rick
 
O2% looks really low. I would double check the air injection and clean out your ABV.

Dynosoar:zilla:
 
Thanks--there's a lot to think about there. I do have the O2 and CO2 readings from the first, official test. The pretest didn't have a printout, I was just scribbling stuff down as he was showing me the screen (so I didn't get CO2/O2 then). You would think they wouldn't change much in less than a month, but then again you'd think the other numbers would't either.

You mention that high NOx is high combustion temperatures--is that because of the Iso-HEET I added? Four 12-oz bottles in 3/4 tank (I was getting a bit desperate). Perhaps that was ill-advised?

I've been over much of the small-diameter vacuum hoses, as I've replaced a lot of them (probably 50-75%). I have been going through the FSM. I was checking air injection first because of my first test results (a bit high CO). I didn't get through everything but no failures yet.

Finally, you said "I doubt the CAT is your problem. On a properly functioning motor, NOx gasses are usually a pass without a 3 way converter." This is very helpful. Thanks.

I guess the next steps are to check the EGR system, and to figure out if the fuel additive was the issue.
 
O2% looks really low. I would double check the air injection and clean out your ABV.

Dynosoar:zilla:

Any ideas for checking air injection flow without the SST that the FSM calls for?

Funny you should mention the ABV. I saw a post about checking it out for bits of the smog pump vanes--might have even been a post from you--so I headed out to do it, secure in the knowledge it was a quick and easy job with four accessible screws. Well, three screws came out fine, the last stripped. Bleh. Have to check it later, I didn't have any time at the moment to get it out.
 
New info, good news and bad news.

Good news: I fixed the high NO with the EGR fixes I just did. The vacuum modulator and the VSV were bad, which probably explains the intermittent problem I had with an intermittent bad idle when warm. I probably had a EGR that sometimes worked (like for the first test), and sometimes didn't (like for the second test).

Bad news: I'm a gross polluter again. Same story as the first test-- high CO. Here's the new numbers:

RPM: 1468 at 15mph, 2437 at 25 mph
%CO2: 12.4 at 15 mph, 14.0 at 25 mph
%O2: 0.9 at 15mph, 0.9 at 25 mph
HC: 91 PPM at 15 mph (max 189), 25 PPM at 25 mph(max 113)
CO%: 2.88 at 15mph (max 1.33), 0.57 at 25mph (max 1.13)
NO: 166 PPM at 15mph (max 1448), 403 PPM at 25 mph (max 1308)

I guess I'm looking at air injection next. The emissions manual has a suggestion for high CO and high HC, but not for just high CO. There's also the possibility that my distributor vacuum diaphragm hoses are backwards. They definitely are according to the emissions manual, but I vaguely remember reading something here that implied that it might supposed to be that way.

Any other ideas for high CO at lower speeds? I was thinking the lower speeds didn't give as much power for the smog pump to work with.
 
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There's also the possibility that my distributor vacuum diaphragm hoses are backwards. They definitely are according to the emissions manual, but I vaguely remember reading something here that implied that it might supposed to be that way.

As far as I know the emissions manual shows the correct hookup for a smogged vehicle. The inner diaphragm is for the spark control (connects to the advancer port on the right side of the carb) and the outer diaphragm is for the HAC.

When a desmog is done, one of the recommendations is to use the outer diaphragm for spark advance. But you clearly are not desmogged...
 
Carb too rich. Do a lean drop. Check timing.


E12 Smog FAQ

Thanks.

Does the mixture normally need to be adjusted, though? My impression from the numerous related threads is that mixture is one of those things that people reach for at the beginning, and generally screw things up. I'm all for doing what needs to be done, but I get the impression that it's almost always something else that's the real problem.
 
Well, your #'s indicate too rich a mix, but could be something else...

When was the last time you changed your oil?

Follow the FSM and do the carb mix adj - it can only help, if done right.

Have you adj your valves ?
 
Update: the catalytic converter seems to be working. (about 200 degree difference between front and rear). I just verified that the standards for CO at least haven't changed, so it's not a case of a problem with the newer cat being needed.

I haven't changed my oil in a while--it usually doesn't get driven much. Probably changed it last time I tried to pass smog. Haven't adjusted valves. Timing BB is to the left of the center mark.

I do have an exhaust leak up front, and a probably intake leak (whistling under load). I would think an intake leak would tend to make it more lean, right?
 
Hi Co readings at 15 mph on the dyno indicate too much fuel being administered from the carburetor. I do not agree that adjusting the idle mixture will affect 15mph operations.

Lets chalk up the second test reading as an anomolie due to the use of foreign substances!

If your air filter and air cleaner assembly are intact and functioning, you are probably looking at a carburetor overhaul to remedy the hi CO readings.

Internal carburetor faults causing Hi CO readings include restricted emulsion tubes and passages, improper float level, leaking power valve.

Edit to answer your comments/questions: Oil change won't make a difference unless the oil is fuel saturated. Other items the same and yes, an intake leak will allow un-metered air into the engine, leaning the mixture. You definitely want to fix that issue.

Rick
 
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