Yeah the "friendly" smog shops where the $200-$300 test option ...cough....was available have gotten far and few. BAR will come down hard on those shops with big fines and pull their license. I have always had to go to "Test Only" aka "STAR" test shops who are not friendly so have to have my stuff in order.

OP, if you have a automatic and your PCM was not tuned for that larger TB...you want to put the stock one back on as tranny failure will soon follow. Stick car no problem. It has no effect on your smog issue either way.

I believe shops can just "test" offline to see if it will pass.

CA now you are only allowed to have one IM monitor show not ready so if you disconnect the battery or clear codes you need to do several drive cycles to get the IM monitors to read ready

 

Well. Took it to the same smog place and I failed. Even worse this time. The picture with the higher numbers was today and the lower number was last time.

I still am guessing, since I noticed the idle ses higher and my laptop shows 0 for iac that there might be a vacuum leak. But at this point I really don't know since I didn't have scan9495 in the beginning to see what it showed before beginning.




Time for a pro?

 

Been sitting on this a few days. Heading to the DMV tomorrow to request an extension on my renewal.

I think at this point, Im gonna hit up an exhaust shop to check for leaks. See if there are cracks before the 02's, Im also gonna get a quote to replace the cat. Im not convinced its the issue, but Im pretty sure mine isnt CARB, and just for my own piece of mind of not having to be sneaky with shops, which I feel like I am, Ill see about getting a new one, kill two birds with one stone.. Prior owner I thnik just bough a 3 inch magna flow from summit.

I also replaced the EGR solenoid, they are cheap, I know mine works, but I figure maybe I should incase it had a small leak or something. So now it has a new EGR and new EGR solenoid. I did another drive test, this time with scan9495 and verified EGR is being called. I also did a second drive with my vacuum guage on it. The second image where I also added IAC


with more activity is when I found a sweet spot to get it to engage. Seems acceleration in 3rd gear would turn it on. It still hardely does anything at 15 and 25mph when trying to hold those speeds so I have doubt EGR does much if anything at those speeds. My issues must be something else. Worst case, Ill just be sneaky and send full manifold to it during the test to get it to engage since Im sure it doesnt during the test loads. Or, see if I can get them to test in 1st year, may have better luck.

After this, I think Ill tackle general tune up items, new plugs and wires and 02's. I noticed the fuel trims do not match so something is off on one of the banks. Im not sure if I will try all 3 myself or just pay a shop out of convenience. But before I think about it, my engine is absolutely filty due to years of leaks. A local shop does engine steam cleaning as a service, they are also a star smog station and auto repair so I might get their opinion.

 

Thoroughly check for a hidden crack in the Passenger side Exhaust Manifold

 

Fuel trims are unlikely to ever match between banks, although flow through the IAC has a tendency to help even them out. On a LT1 you typically want 50-70 IAC counts at hot idle with nothing on. If you are vacuum leak free, back off on your throttle body minimum air rate screw until the IAC counts rise and the IAC takes control of the idle speed correctly. I would send the injectors out and get them cleaned and flowed. All it takes is a weak flowing injector to get a lean, hot burning cylinder and that will spike the NOx readings. While they are off the car, pull the intake manifold, clean out all the EGR passageways and all the gunked up carbon. Clean the intake ports in the head with B12 carb cleaner. Then put it back together with new gaskets. Every GM vehicle I have ever messed with that had a vacuum operated EGR valve would stumble hard to the point of stalling or almost stalling at idle when the EGR valve is manually opened all the way at idle. If the car/truck did not stall it would run with a very noticeable lope like it had a massive cam from all the EGR dilution. Given you saw very little change in operation, that is a sign that your EGR system is caked up with carbon and not flowing like it should. I would also soak the tube off the manifold in B12 overnight to ensure it is clean.

If you have an aftermaket cat back, I would also suggest an aftermarket EGR that comes with many sizes of flow restriction orifices. Try a washer that has 20-30% more flow area than the one the stock valve calls for. I had a couple of TBI engines with headers, high flow cat and a low restriction muffler that would throw EGR codes from the reduced back pressure and opening up the flow area of the valve corrected the EGR operation, eliminated the EGR error code and drastically cleaned up the NOx emissions. The factory EGR system setup relies on the designed exhaust backpressure to help push the exhaust gases into the intake manifold in the proper flow range. Once you alter the backpressure the valve becomes less effective.

 

The EGR and solenoid is a specific part # for the F body stick car, There is another EGR for automatic. Make sure you have the right one

Post 45 has some very good 411.

Paying a shop to find these kind of issues is a deep pocket endeavor assuming they even know how and can do it. They typically change a bunch of parts that have nothing to do with the problem then when you fail again you are forced to see the referee. That is a death sentence.

leaks in any of the intake and exhaust components will FU fuel trims and if that is the case one bank has consistently higher #'s above the 400 range than there is a leak somewhere pre 02 as the PCM is commanding fuel.

steam cleaning an engine like a LT1 full of electronic sensors and parts can be a fatal move. Elbow grease, toothbrush, rags and a hand wand that emits mist you can precisely direct away from these components is a better method. Harbor Freight has a hand wand that you use a compressor attached to it and the wand sucks water (hot with a small amount of disc soap in it) from a bucket.is very effective and can be precisely applied.

 

Thank you Fast335 ***** for your replies.

I am pretty certain I got the right EGR. I can found a post from Shbox indicating 17113373 is for a 93 6-speed, and that is what I bought. And the stamped number matches my original. I got it from ebay, listed as NOS. As for the Solenoid. I didnt check as had as I maybe should, I just referenced rock auto and got it from amazon, part ACDELCO2142207.

Your two posts have given me the boost I think I was needing. I just couldnt think of any next steps. I dont mind trying, but I don't know what is next.

@fast335 I do have a Borla catback, the one with the removeable plates. And I know by cat is not the original. So I feel, maybe there could be back pressure issues as I read that. I dont know if it will help, but I can put the full plate in so its not a straight pipe for now incase that helps. And yes, my rpms do drop when I press in the egr valve, but is no where close to stalling out.

@***** As for cleaning, I didn't realize that was so risky to steam clean. I could take some time I guess and clean it myself would long brushes. Its just so grimey. But I would want to do this before trying to do the intake manifold. But I found a youtube video of how to remove it and it seems doable. My thoughts at this point, being my goal is to try and fix the issue versus skip by via tricks is maybe the following.

1. Exhaust shop, to check for manifolder/exhaust leaks and inquire about a new catalytic converter (since mine is not CARB legal anyways) Then replace 02 sensors.
2. Clean top of engine so I can actually see all the bolts and reduce grime.
3. Remove fuel rail and injectors. Get injectors cleaned somewhere as Fast335 suggested and replace o-rings. Maybe with this removed I can test fuel pressure. Might as well replace the fuel filter again incase its clogged a bit.
4. Remove the intake manifold, deep clean all passages, also I can finally tighen the EGR properly which Im still not convinced is tight enough as I simply havnt found a good way to crank on it.
5. Clean egr pipe as suggested.
6. Clean my BBK throttle body. I need to check my original TB which I have, the prior owner gave it to me. I dont know if it has the original IAC and other parts or if he moved them. Depending on the condition, might consider just throwing the stock back on incase the bbk is not tuned right like you say with the IAC screw positions.
7. New gaskets.
8. New plugs. I never checked them after I bought the car 6 years ago. The prior owner didnt have maintenance records on them so I dont how old they are. I may as well do a compression check while at it and then replace the plug wires.
9. Maybe have a shop check for vacuum leaks incase I dont have the tools to do that right.

Does this work flow make sense? This is not a daily driver so I have the time. Not so much the skills, but I bought this car to also learn mechanics on. I try to do everything possible just to learn.

 

the potential exhaust leaks would be pre 02 to affect tailpipe emissions....that area of the car is typically a foreign language to any "muffler shop".

You don't need tools to find vacuum leaks...you need eyeballs and ears.

I propose you do the looking and checking yourself as shops don't give a F other than throwing a bunch of unneeded parts and spending your $.

I would focus on the plumbing of your air pump & check valve plumbing at the car for cracks, leaks. The L shaped vacuum hose under TB and any vacuum lines running along intake manifold. Cracked exhaust manifold or broken bolt specifically on rear cylinder.

Cleaning the engine is always a good idea but not something that is likely to resolve your smog issue.

cruzinperformance.com is who I sent my injectors to for service if they are still in biz. Rich was the guy

changing the CAT and 02's will likely have the biggest effect on passing smog test.

if your scan shows fuel trims are fairly equal on both banks that is a good sign you do not have any vacuum or exhaust leak pre 02's. After 02's does not affect smog test

 

Well, I suppose I should cap my borla with the full plate. Perhaps if I quiet it down I can hear better to listen for leaks.

I know the air pump works at minimum, Im thinking you are saying the check valve because if that is letting exhaust leak by it could be an exhaust leak leading to incorrect 02 readings?

I will recheck the vacuum lines again to find leaks. But regarding the dirty engine. My only thought on this was to facilitate intake manifold removal. It would be my first time doing it, and its just a bit dirty and I figured doing so would let me better see what Im doing. But I have various brushes, like thick pipe cleaners meant for this type of cleaning. Ill work on the cleaning myself, reveal the bolts and work on removal.

Thank you for the reference, I will check them out regarding injector service.

Here is a 30 second clip of scan9495 running to get an idea of all the metrics. This is with the engine up to temperature. I took this a few weeks back.

https://photos.app.goo.gl/KVocGKuvhRvzj64y7

 

have you replaced the o2's yet ? If not, seriously, just do this first. Replace them and it is going to pass. The car is reading lean because of old o2s. Also make sure the air filter is CLEAN. and 91 octane with some chevron techron fuel cleaner. Stop wasting time and effort just install new o2s LOL. PLEASE !!!! this is assuming the EGR is new, I think you said it is.

 

I should have just done it before the 2nd test but after seeing it will be tricky on the passenger side I had hoped with what I did so far it would pass. But I'm just afraid what happens now if I fail a 3rd time if I only do o2s. I don't know if there is a limit for how many times I can fail?

So I want to do the o2s and do the cat, since it's not carb legal anyways, and pull the intake to clean it out and may as well flow/clean injectors with it all out. I figure this should surely do it. And then a final exhaust vacuum leak check and try again.

 

CA has "grants" for failing cars, they literally give you money, to "fix" smog failing cars. I would for SURE look into that, before spending $1000-2000 on a cat. I believe you can test as many times as you want. the DMV will just keep giving you 30 day permits, to give you time to fix it. no big deal.

The car is reading lean, for many possible readings, and that is why the NO is "high". sometimes this is caused by vac leaks. If you had a vac leak enough to cause it to lean out, you would notice a high idle. Is it idling where it should be ? if so, that rules out the vac issue.

next on the list is going to be o2s. A lazy o2 will not throw a code. and it may even be hard to find with datalogging. if the o2s are older, regardless of smog, it would be a good idea to change them anyway. keep in mind after install, you will have to drive the car 100-200 miles in order to "clear" the monitors with the new o2s installed.

next up would be the cooling system, and the catalytic converter. Is your car temp running where it should be ? high engine temps can cause high NO.

The easiest thing up next, by far, is the o2s. I wouldn't mess with intake or injectors, you are opening a hole you don't want to go down, and cause further potential issues.

 

oh, and buy AC DELCO 02s ONLY !!!! no exceptions on this one, anything else will fail quicker than you would like.

 

CA OBD2 CARB CATS are about $500. I have the Magna Flo ones. They come with a 2 part tag you mail in to register them and keep other half in your car to "show" LEO if questioned. They have a 5 year guarantee if you fail emissions, they replace. If shop installs them they mail in the tag

 

Yep those are what I purchased. Ac Delco AFS21.

MY 1993 is obd1 and I read those have maybe lesser requirements? But that is good to know. I wish I had paperwork to determine what I have. I don't have a receipt from the original owner. But that is good to know.

 

OBD1 CAT is even cheaper than OBD2

 

Especially if we are talking California cats.

 

Are these o2s original? I pulled the easy drivers side one today. Working on figuring out the harder passenger. May have to remove the starter it seems like.

 

neither one looks like a AC Delco AFS 75....the ONLY one to use.I get mine on Amazon for about $35

 

This is probably of no use to you, but my completely stock 94 TransAm (from Texas, no less) just passed smog with flying colors the other day! I didnt think it would pass, especially without "california emissions" but I tried it and boom! It passed! I was very surprised. I even purchased a CARB approved CAT, new 02 sensors, but turns out, I didnt even need them. All I did was an oil change and air filter prior to smogging.