1996 Mustang, My greatest fear has finally come true!

[Rivguy]

My Mustang, with well over 200,000 miles, failed the smog test today. It failed the exhaust pipe sniffer portion of the test. It didn't set off the CEL and I haven't checked for any codes. yet.  The engine runs great, doesn't smoke, or over heat, and idles really smoothly. I took the car on a couple of 250 and 350 mile runs this Summer. The car has been sitting in the garage since Sept or October.  I needed to get the car smogged to complete the registration for next year. It wasn't like I cleared a code and rushed down to the smog shop!

I had it smogged this past Summer ('22) when I had tried to sell it, and it passed with no issues. Mileage since then is probably only 700 miles or so. I plan on comparing the results of the two tests, noting the margins that it passed last Summer's test against today's. I suppose that at some point an engine can still be running good,  but has worn to the point that the hydro carbon levels in the exhaust are too high to pass. Or maybe it's the catalytic converters that have gone bad. Right now, I'm just bummed about it, but I'm not going to rush into anything. Luckily, I have plenty of other cars to drive. 

I've kept both of my Mustangs in the garage since before the holidays, I wasn't going to get them dirty with all this rain! Today has been the first sunny day in weeks. A dry pattern is predicted for the next week. 

[Luv2Wrench]

Do you have the results to see how much it failed by?  Can you keep trying until it passes?  If it is close this will probably work.  I know that my car likes to throw a CEL with rapidly changing in January but cures itself by February when I have to take it in for testing.  I wouldn't be surprised if your issue was just weather related and could even have been the testing machine being affected by weather.

[Rivguy]

I have the two prior smog tests to compare my results with the latest test.

On 12/07/20 at 214,204 miles I had it smogged for '21 registration. Passed.

On 04/20/22 at 216,278 miles I had it smogged for potential sales. Passed.

On 1/17/23 at 217,513 miles I had it smogged for the '23 registration. Failed. By one point in max H/C @15 mph.

 

Prior to the April/22 test I had replaced the plug wires, coils, spark plugs, and air filter. On the current test it failed the roller h/c check. I'll address those margins. The max permitted at 15 mph. is 50 PPM, at 25 mph the max is 34 PPM

On Dec '20 the measured results were: 15 mph. 35 PPM,   25 mph. 14 PPM  Passed by margins 15 &20 PPM

On April '22 the measured results were: 15 mph. 31 PPM,   25 mph. 14 PPM  Passed by margins of 19 &20 PPM.

On Jan  '23  the measured results were: 15 mph. 51 PPM    25 mph. 25 PPM  It failed by exceeding the max reading @ 15 mph. by 1 PPM. It passed with a                                                                                                                                   margin of 9 PPM @25 mph.

 

Mileage since 12/20 was only 3,300 miles. I had been monitoring the margins for passing the test, looking at the '20 and '22 test. I felt that I still had plenty of room for success, since the car is now completely a hobby car and it will accumulate mileage even slower in the coming years. I bought my '06 Mustang to use as a driver and figured that I could still own the '96 for many years without having to rebuild or replace the motor. 

 

As I mentioned earlier, the car has been sitting in the garage since Sept. or Oct. with only an 1/8th of a tank of gas. I'm wondering if due to the cold and the extreme rain, maybe there was a lot of condensation in the tank, I didn't even add any new fuel before the test. The battery had also gotten so weak that it couldn't start the car. I jumped it and let it run for about a half hour before taking it to the test center which is ten miles away. It didn't have any problem starting the car when I tested it before leaving. Usually I will add at least a half tank of fresh gas and use the car everyday for a few days before taking it in for smog. The low voltage might have had a bad effect also. I had a ton of problems with my '07 Mustang when the battery went bad on me.

 

After failing the test I added a half tank of new gas and half a bottle of Techron additive. After I use that up I'll add another half tank of the good stuff, Chevron, and the rest of the bottle of Techron, and drive some more.  I've got 90 days for a free re-test. If it doesn't pass, then I'll have to consider checking the catalysts and other things. 

 

These will become more common problems as collectors move on to 1990's model cars. Why did I sell my '70 Mustang? 

[jp1gt]

run some sea foam into the intake. I have seen some unbelievable results

[EmTee]

How are the spark plugs?  If it has been awhile it might be worth changing them.  Occasional misfires could put it over the limit.

[31nash880]

Found this a few years ago replacing engine in my 95 camaro. Was surprised when I took the throttle body off how much carbon was on it. I guess when you take your foot off the gas it sucks back some. Was almost fully clogged. No check engine light or misfire.

[avgwarhawk]

Replace the O2 sensor.  These get lazy over a period of time. Have trouble reading the exhaust yet don't throw a code.  Arrive to the test with a good and hot engine. 

Edited January 21, 2023 by avgwarhawk (see edit history)

[LARRYCAROL]

If your engine has egr system they can affect h/c readings. Valve or passages partial clogging can cause those readings and don’t always cause fault code. 

[Rivguy]

I appreciate all the suggestions. Checking the EGR and changing the Oxygen sensor look like my next step. 

[Rivguy]

Update: Good News, Today, my Mustang passes it's re-test! The passing margins are even better than the test that I passed in April of '22.

 

After the failure, the shop gave me 90 days to come back for a free re test. As I had posted, the car hadn't done many miles since the last test in April '22.  To prepare for the retest I put in half a tank of fresh gas, added half a can of Techron additive then started driving to use up the old gas. After I ran that down, I pulled and cleaned the MAF sensor, added another half tank of gas, added the rest of the Techron, and drove some more. I went by the shop armed with my past tests to discuss the matter with the tech. I asked about the possibility of bad cats. He explained that the results weren't consistent with a catalytic converter failure in his experience. He asked if I wanted to try the retest and I told him that I still had quite a bit of treated gas left. He advised me that the additive would be detected by the machine and would result in an instant failure. His advice was to burn all the treated gas, then run some good premium gas through the car then come back. 

Yesterday, I drove the the car until the level was quite low and added four gallons of Chevron premium. Then I drove it for 70 miles, and added another four gallons of Chevron premium this morning and drove the car for an additional 40 miles. Total mileage was 374  since the last test. Unfortunately, the shop was backed up and I would have to wait over two hours for the re test. It was worth the wait. It passed and the margins were better than last year. 

At 15 mph. HC is allowed 50 max, mine was measured at 22 ppm.

At 25 mph HC is allowed  34 max, mine was measured at 7 ppm.

I really feel that I dodged a bullet, but I should not have been so lackadaisical in my approach to the original test. Lessons learned?

Don't let the car sit unused for four months with a little bit of old cheap gas ( I always use the cheapest) in the tank, and then go directly to the test station. I should have started daily driving the car at least a month before the test, filling it with fresh gas and maybe some gas additive. Run the tankful of treated gas completely through the system.  Cleaning the MAF sensor was easy and could help. Then I would start running it on better gas and maybe run half a tank of premium through the tank and keep premium in it for the test. I would also be sure to run the car for at least 30-40 miles before I arrive at the station. 

It appears that my original premise, that the car should be able to pass subsequent smog tests in the future, since I will be adding very little annual mileage. and the margins are still pretty good, should hold true.  At least, that's the hope.

As I was leaving, I told the tech, "This gives me 90 days to sell it, or almost two years more to drive it!"

Breathing a lot easier in San Jose.

Edited March 10, 2023 by Rivguy (see edit history)

[Rivguy]

After the car passed the smog test I put it back in the garage, My goal was now to put some miles on my '06 Mustang and my newer daily. I managed to put about 400 miles on the '06, mostly on a trip up to Placerville. Then the '06 went back into the garage.

Today I decided to take the '96 out for a bit of exercise. The battery had gone pretty flat and I needed my jumperbox to get it started. The battery is a bit over four years old, so I imagine a replacement will be needed soon. I had set up a float charger connector on the battery but neglected to ever hook it up. Once I got the car started it would restart after running for 15 minutes. I drove it to the Barnes and Noble Bookstore about 12 miles away, but I kept the jump box in the trunk just in case! 

I had discovered that my Navigator had broken both of it's muffler mounts, I'd tie wrapped and used wire to hold them up temporarily.  I bought some new mounts on Amazon but I realized that I wasn't going to be able to install them without a welder. I found a muffler shop in San Jose, Abuelo's Mufflers, and they did a great job welding in the new mounts for 20 bucks. In fact the tech asked how much I'd paid for the mounts, then told me he would have done the entire job, including the new mounts for 20 bucks! 

I was satisfied with his work, so I returned with my '96 today. I had done an earlier Mickey Mouse repair on the pipe hanger with some coat hanger wire and a couple of hose clamps. It wasn't noticeable and it held up for over four years. 

I got there and was watching the tech build up a custom set of side exhaust duals for a Tahoe by eyeball. After removing the stock muffler he mocked up the muffled exhaust tips, and selected a length of strait tubing trimmed it, then put it in the bender, held it in place. over the rear axle. He trimmed a bit more, bent it again, flared the end and welded it into place. Pretty impressive.

The guys at the shop and the other customers were very complimentary about my Mustang, which always makes me feel good. Even several young guys with a Honda and a Nissan. 

This time it was the other tech that fixed the problem. He only had to weld the hanger back to the tail pipe but he again charged me 20 bucks. I guess that 20 bucks is kind of the minimum charge, but i'm not complaining. After I got home I hooked up the float charger for a few hours. I'm not looking forward to buying a new battery, yet. 

[Luv2Wrench]

Every year I do the emissions dance with my daughter's 1998 Mercedes CLK 320.  This year we reset the CEL and she drove quick start/stop trips before heading to the tester.  She's mastered the process by now.  This year, however, when she pulled in to get the test the guy said "No more tests, car is 25 years old".  One less problem for us now!

[Rivguy]

I sure wish that we had that rule in Ca. Only cars earlier than 1976 are exempt. It's kind of amazing that cars that are 25+ years old with high mileage, 217,000 miles, can still run clean enough to pass the tests. Annual mileage on my '96 has gone way down since it was retired from Daily duty, combined with my being retired. I anticipate that it won't reach 220K for several more years. 

[Rivguy]

My Mustang has a safe secure place in my garage, so it stays nice and clean. It's getting very close to hitting the 218K mark. I hadn't driven it in quite a while, I was trying to put some miles on my '06. I will try to take it to some local get togethers, maybe someone will be interested enough to want to buy it. I still really like this car, and have invested a bit into it, I have no interest in giving it away. I'd just rather keep it. My Wife thinks that is silly because I told her that another car that I have wanted forever, in very good shape with low miles, just came up at a fair price. I could just buy that other car, but I don't want hobby car #4. 

Since I retired i don't drive a lot during the week, and all my cars except the truck, sit around quite a bit. Back when I was working I would switch off and drive each in a one week rotation. Now it seems that they all sit at least a month at a time. 

I decided to pursue a " Deus Ex Machina" approach. I reached out to the seller of the car and offered him a trade for my Mustang, I told him that I'd put money on top of the car. He replied that he was trying to downsize, and wouldn't be interested.  I'm just going to sit back and see if he comes to me, I already know how much I'm willing to put on top. It could be a pretty good deal for him if he doesn't mind putting in the time and effort to sell the Mustang. If it's meant to be it will work out, if not I'll just take my time and try to sell the Mustang outright. I basically gave my three Jags away to clean out my garage, i replaced two of the cars so far, and don't really need anything else. Time will tell. 

Buying cars is fun, selling them is not!

[Luv2Wrench]

We all need 12 bay garages.