Been tinkering with my mothers 1991 camaro. It came to my house in sad shape. I changed cats first since it had hollowed shells. Then I fixed a bunch of cooling leaks. Its idles great in my driveway but a little rich smelling. Only have a week left on her temp plates. Where to start? Wires appear good, recent changed. Idles nice at 600 rpm. I changed oil before I went and drove 26 miles into the test station. It blew double/triple the limits for hydrocarbons, co, and NOx.

 

How long ago was the O2 replaced? Also, does the temperature sensor work? Unfortunately I'm not an expert on emissions, so I can only give general suggestions.

 

Replace the 02 sensor, ensure all other sensors are good, including the EGR. Ensure the A.I.R. system is functioning and that the smog pump is there, installed/hooked up, and running correctly.

That's where I'd start.

How does it run when you drive it? Fine other than the emissions issue? Also, never trust your "nose" to tell if the car is running rich.

 

Changed that out tonight (o2 sensor). Can not communicate with the ecm at the moment. Its not cooperating. The data line isn't steady. Damn thing just runs so smooth I don't get it.

 

What sort of scan tool are you using to communicate with the ECM? I assume since it's a 91 you are using the 8192 baud interface?

 

All emissions equipment is there and seemingly functional. Air is working. Doesn't seem to have any vacuum leaks. It has been back yard mechanic stored for 7 years and I keep finding smalls things and fixing to proper specs. I've just never seen new cats fail still.

 

I have a snap on MODIS. It communicates with all my other firebirds but this one just won't connect to the ecm. I have another 91 with an 89 maf ecm and it reads just fine. I can even read some airbag data so it can be all dead.

 

Egr holds vacuum, solenoid is good. I'll check timing tomorrow evening after work. Took this on to help out my mom but its biting me in the ***. It has new injectors. Looks like a recent tune up.

 

I've heard of these cars having issues with the computer that cause behaviors that are difficult to track down. If it's not communicating, perhaps the chip needs reseated? Seems weird that it would not be communicating. Do you at least get blink codes if you short the A and B pins?

 

Yes. Code 12... I have removed and installed twice as I've seen that in the past.

 

Will update any further suggestions tomorrow after work.

 

What engine is in this 91 Camaro? Is it a tbi 305 or 3.1L?
If its a tpi or mpi, check the fuel pressure & bleed down rate. A bad press. regulator can skyrocket the emissions. Check ecm grounds too. Make sure the ignition timing advances when you rev it. Is the engine running cool? It should be running at 190-200 while going down the road.

 

350 tpi. I have not checked timing yet. I needed a baseline after changing the cats to see what I was up against. It runs 195* going down the road according to the gauge. All grounds were removed and cleaned, painted over. I'll hook the gauge up and check the bleed down rates. I'd like to see the engine data to see how the o2 readings look. The original ecm was found and will go back in tonight. Hopefully it tells me something.

 

OK, finally was able to find a broken wire at the aldl connector and hooked up. Full data was read and appeared to be normal. I replaced plugs, replaced o2 after the test. Also dumped oil again. Replaced a bad CTS sensor. I did notice that my int says 128 but blm reads 108. Takes some time to go into closed loop but its only idling in my driveway. Data wise the map reads 17"hg at idle. I replaced a bunch of vacuum lines just for looking crummy but I have that stuff in bulk for my other cars. Advance at idle is 19* and does change going down the road but hard to look at and drive. It was 9-10* before I changed the OEM plugs on 6&8. It has edelbrock tes headers with all emissions there and functioning correctly. I plan to run thru again tomorrow and would love to hear anymore questions from other members. I've bounced ideas off of you guys for years and have always found my issues just from a question I forgot to ask myself.

I didn't get a chance to hook up my fuel pressure gauge. Its getting cold in Connecticut and I work during the day. I'll do that this evening as I'll have a few hours.

 

And it has failed again. I'm guessing eastern cats aren't good enough? It now runs very well but it has also sat for years. I tried a few bottles of dry gas also.

 

What were the scores this time? My car failed 5 times while I was trying to fix things before it developed a rod knock. I had just found some vacuum leaks around two injectors and was looking forward to see if that changed the scores, but then the rod knock started.

 

Hc- 138 ppm, limit- 53ppm
Co- .34% limit- .28%
nox- 1145ppm. Limit - 614ppm.
This is the Connecticut test standards. I wonder if they even blew that low when new

 

Make sure your base timing is set to 6* btdc (Should be close to what the manual calls for). You can retard the timing to help burn off the Hc's. Not sure if it will bring you in to spec or not though for that.

I'd swap the EGR anyway, even though it's holding vacuum. At this point, might as well make it "new".

The smog pump is hooked up and the diverter valve is actually diverting the air as it's supposed to?

What were the original readings? Has it gotten any better?

 

It got better from last. I cleaned all the egr ports also. I should have checked base timing. All emissions components are there and functioning as they should. It has smog headers.

As usual, a favor turns into a nightmare.

 

With it idling, apply vacuum to the egr with a vacuum gun. It should stall or idle really rough.

 

It stalls if I don't release the vacuum.

 

Wow, that HC is tight...but NOX is usually a product of EGR, but lean conditions (high combustion chamber temps) as well...sure you have all vac lines /leaks fixed...there something else with Nox...but my memory fails me...wait...maybe timing too far advanced?

But dang, I thought things were tight in in nazifornia...lol!

 

Our state wants everybody in a new Prius or civic. They explain how our cars don't raise enough taxable revenues and ct is behind again with its spending issues. I'm gonna order up some magna flow cats Monday and remove these. I've heard better reviews on those. I'll take apart the top end again and replace gaskets again just to insure no leaks but I didn't notice any with carb cleaner at idle. I did replace 90% of the vacuum lines. I also need to check timing as was mentioned above. Wife is dragging me all over lately...

Car also needs to be driven. The tech told me to go hammer it for a while. The reg is up today on the temp plates so that gets kinda hard.

 

Tee in a vacuum gauge into the egr vacuum hose to see if it's getting vacuum while your driving it.

 

I'll have to keep it local as the plates are up. Can't legally drive it anymore. If it passes she can put plates on it.

 

I would swap the cats to the newer style our old cars didn't have the best... not to mention how old that ones to to be... you would be surprised how much a new cat can improve your emission numbers

 

I used two less then 500 mile eastern cats. I consider that new as they passed very low on my other firebird. I'm most likely gonna order 2 magnaflow cats and try again

 

If your BLM is at 108 it's running pig rich. It doesnt matter what kind of cats you put on it they wont clean up that kind of error, you need to find out why it's so rich, CTS, O2, even IAT maybe. What do these read when you scan it? check your fuel pressure also a bad regulator can make it run rich for sure.

 

Once this cold snap passes I'll pull the plenum. I'm iffy on how well the p.o sealed it. They used rtv around the throttle body instead of a gasket. (I replaced the gasket and brush cleaned what I could). If it was my car I would have pulled it to redo it correctly. My 91 tpi ran very clean considering but I also have a normal budget. I'll check fuel pressure and dropoff in a day or so. Seems life gets in the way.

Max, the CTS initially read -40, I changed it and with an ir heat gun its only +/-8 degrees. O2 has great cross count speed, iat read 75* on a 60* day when warm. Again vacuum read 17" thru the comp, I'll hook up my gauge to verify. I'm not familiar with speed density. I'm more a maf guy

 

Also the injectors were replaced at some point. How can I determine the flow rate? I'm trying to fix 9+ backyard mechanics hacks from over the last 7 years.

 

No doubt if the injectors were replaced with the wrong ones it could be your problem, pretty hard to ID them unless you can read a p/n which is usually stamped into them or some ford injectors could be identified by color. pull the vacume line off the regulator sometimes if the diaphragm is torn you will get a drip of fuel from there.

 

These are a black body injector similar to the stock ones. I run bosch III in my cars. She complains it burns a tank very fast. Ill pull the rail/injectors and prime the system over cardboard. Maybe a leaker. I have to resealed the plenum and runners correctly anyways so what's another step. Prolly do that this weekend.

 

Heh move to Pennsylvania. Out here all these cars get is visual. No longer do they do tail pipe emissions.

 

Lol. My 91 won't pass. My mothers has to for another 2 years I believe. Everybody in this family drives an f body pretty much. I bought a 2000 to wait out this emissions crap and to finish modifying mine. I'll have cats on mine but I won't be running rich. Ct wants to fully adopt California standards tho and that scares me

 

Wow you need to move lol
I live in Tennessee and our limit is
Hc-220ppm

 

Lol. Too many tree huggers up in the northeast. The limits allowed actually drop every year. People are blunt up here when they say they want them off the road. Not enough tax revenue since they tax everything to death up here

 

Funny that they bitch about car emissions when trucks belch out 5 times as much. But lets not forget about industry and other polluting sources. It's the person driving a 25 year old car that's destroying the environment. PA for the most part is pretty easy on these cars, but the farther you go up north the restrictions get stricter.

 

I'd go outside and work on this car for a few tonight but, 25* just doesn't do it for me.
Also, its funny you mentioned that. Our shop truck is a 93 k2500. I just went thru emissions puffing black and overheating. Its allowed 6x the limits then a 91 camaro. Both 350's

 

I was finally able to get a fuel pressure reading. It shoots up to 47 no problem. Key off it drops to 25 or less in less then a minute. Surprised to see no fuel coming from the regulator. I did find a vacuum leak and need to fix that first. I'm pulling the egr to run a camera thru the lines. Can't hurt? I'm also gonna run my camera down the base.

 

Number on injectors reads 01d036b. How do you decipher that?

 

After resealing the intake, replacing all vacuum lines, cleaned out all ports/runners, checking that egr valve is good and solenoid is functioning well, pressure regulator isn't leaking vacuum, injectors aren't bleeding down it switched from rich to lean. Int reads 131 and blm is 134. I will check timing tomorrow since my timing light is FUBAR. Idle is high as well which says vacuum leak to me but I may need to do the minimum air setting again.

I can't believe how much build up can happen coat the walls of these things when not taken care of.

 

Sounds like so much work to simply get the dang car to pass emissions.

 

Sadly ct offers a waiver but you have to have the repairs done by a ct emissions certified shop and I think its up to $975 out of pocket. Its only a possibility that you'll be granted a waiver tho. They want them off the road. End of story. I didn't think my moms car was in that bad of shape but I'm guessing it was at this point.

 

Not enough tax revenue? How so? Newer cars like Prii burn less gas, and taxes on gas is what pays for roads to be built and maintained. If anything, it's cars like these and big *** dually diesel trucks that are keeping the roads going somewhat. Roads and bridges all over the country are crumbling. If the tree huggers had their way and we all drove gas-sipping vaginas, the roads would really be gone.

 

We pay a yearly property tax as well. My 91 is only worth $157 yearly so they consider it useless. Hell I bought my car for $500 6 years ago and had to pay $350? sales tax due to its mint condition worth at the time even tho mine was a shell. Also, my 2000 formula m6 gets 17-18mpg. My 91 formula gets 22mpg so gas tax argument out the door. Lol.

But seriously, does anybody know how to convert the data reading for the map sensor (9.2) to an actual vacuum reading. I am guessing 19.5 inches hg ? That's the data reading I'm concerned with. I swear it said 11.3 before I changed the gaskets but it could be another car I was working on. The wild swing to lean has me kinda nervous. I guess 131 int isn't too bad considering I haven't been able to verify the timing is good. Whoever changed the injectors backed the throttle screw full open. Damn thing read .91 at idle! Now its .60

 

OK timing is 5* btdc. Finally got a working timing light. Vacuum is 22" at idle with timing connector unplugged. Hits 21" with it plugged in. Still idling high as hell. Gonna pull the left runner again. Think I pinched the gasket.

 

You have high HC, NOx and CO? That doesn't typically happen. How long did you run the cats on the car before you got that second test done?

-Generally- the only time you will see High HC, NOx and CO at the same time is retarded cam timing iirc. Since your CO isn't too high, playing with the timing should work, but I'd also look into the MAP sensor.

Not having the O2 and CO2 readings doesn't help.

 

How much can I safely go back with the timing? I normally stay where its supposed to be. I do question her map sensor. That's why I hooked up the mechanical vacuum gauge. Is 20-22" good idle vacuum? My 355 pulls 18" but I have a cam and it seems OK? I'm trying to post as much relevant data and info to assist with ideas. I ran the car for maybe 50 miles? She had temp plates which kinda restricted me. I've been idling it in the driveway since the idle is currently 1200-1400 for some reason. I may swap a known good map and tps just to be sure. The high idle started after I cleaned the intake manifold and unstuck the IAC valve. It seems to have been replaced recently but it had so much carbon buildup it physically stuck in the throttle body.

 

A couple of things...

Your vacuum reading at "idle"..is not real, since you say it idles at 1400? RPMs...so you now need to square that away.

You need to find out what timing allowances are given for your test...i/e here in Ca, you are only allowed plus/minus 2 degrees for setting...so even if my car was cleaner at 10 ATDC, I'd fail.

 

Yea I realized that after. I'll mess with it tomorrow and get back to the boards. I don't know if they check the timing in ct. I know we mirror ca for most of it tho