There would be no pressure in the exhaust system even with a fully clogged converter after sitting for a brief moment. Even with a clogged cat the engine should start and run although it may only be for a few seconds before bogging down.
I’m still not fully on board with the clogged converter thing seeing as how this is described as a running with no hiccups to a no-start in one swoop.
The scenario is later described as the vehicle running fine after a couple of balky starts before it went on the tow truck to the second shop.
I wonder if this is a residual fuel pressure loss issue or intermittent ignition problem.
I agree. @Tester’s advice is the first thing to do. At least that’s what I do if I had this problem. Before going on an expensive parts replacement spree, make absolutely sure it is one of the converters that is causing the car not to start and run correctly. If it runs ok with the exhaust system temporarily disconnected (wear ear plugs) then the shop can gradually add the exhaust parts back in until they find the culprit causing the clog.
I presume this car was sold originally in Calif, so that’s why a Calif replacement cat was installed at some point. They probably have to do that, otherwise the ECM will detect there’s something amiss, and the check engine light will stay on all the time.
You have a pre-cat with a honey comb like substrate that breaks apart and gets sent down to the main cat. This busted up substrate will sometimes align correctly with the main cat substrate so the engine runs. Then when the engine is turned off, the busted up substrate falls at the bottom of the main cat. Then when the engine is restarted, the busted up honey comb of the pre-cat no longer aligns with the honey comb feature of the main cat. And you have excessive back-pressure.
The last time I saw this happen was on a Ford Fairmont.
I just saw this a couple of weeks ago on a Kia Sedona. Towed to shop, lost power and died on freeway. Started and ran fine around the lot for 15 minutes, but went to accelerate out to the street and stumbled and died, would not restart until it sat for a few minutes. Ended up replacing one “mani-cat” and the rear cat.
The bank 1 cat had been setting a fault code for some time following a cylinder misfire that went untended to for some while.
An interesting aside to this story…these folks bought the van brand new but brought it in because of a misfire and possible issue with the variable cam timing system at 55,000 miles. I suggested they see the dealer, since the car came with a 100,000 mile powertrain warranty.
They then complained to me that the dealer had voided the warranty because they had only changed the oil 3 times in 50,000 miles. So as a result they now refuse to deal with “those jerks at the dealership” and come in here for repairs.
The logical progression would be that since oil changes are seldom done the engine oil level may get away from them due to progressively worse oil consumption and scatter the engine at some point.
Once that happens asemaster, they may swear “that jerk…” who replaced the cat is the cause of the oil consumption. I’d like to say that with humor but unfortunately things like that happen all too often.
My brother-in-law had a Ford Fairmont and the exact thing happened to him. He kept driving his sluggish car until the floor carpets went on fire; the cat was so close to the floor and with no heat shield the floor got very hot. The car had about 60,000 miles on it.
I tried to explain to him what had happened and he swore never to buy another Ford.
The Fairmont was the one where the owner disabled the smog pump, and then couldn’t figure out why the engine started losing power the longer they drove it.
But I do remember getting a vehicle in where the front cat broke apart. Because I had a hard time locating a replacement. There was no such thing as the internet back then.
So, I apologize for not being able to remember every small detail from thirty-some years ago.
And The Rest of the Story: The new shop had NO problems getting the car started and running (no big surprise there from my point of view). The Y pipe and rear converter need replacing, but the precats are ok. All indications are a slow progression, no sabotage. Computer had registered 4 different exhaust codes but not enough to trigger the check engine light yet. Saved myself about $1200 by having the second opinion! Also, the expired state inspection sticker that was on it was counterfeit (not unusual around here, though, according to the inspector … who also told me the car should not have any issues with inspection once the exhaust is fixed). What a learning experience! Thanks for all the help.
Update:
Have had the converters replaced and Y-pipe, had a fuel system cleaning and tune-up, oil change, and passed state inspection. Whew. Next chapter. No power when shifting out of park or idle. Car now sputters/dies worse than before (but did run enough in the afternoon to get pulled around the building) Even mechanic says it is not consistent.
Found a piece of paper in the trash that the PO left in it: says “4 computer codes need correcting: p0171 fuel system lean p0174 fuel system lean (Banks 1 and 2) p0102 Mass Air Filter sensor circuit low frequency detected and p0113 Intake Air Temp sensor circuit high voltage. Exhaust system needs fixing to be corrected.”
If I replace the MAF, what am I looking at if this does not fix the problem? Air intake ducts? O2 sensors? Just need to know what to expect next. Thanks!
I would clean the MAF first, these are pretty expensive to buy and there is a spray cleaner you can get at most parts stores for about $7 that usually solves the problem.