Missing, serious lack of power

[km2002]

Greetings, all. I've replaced everything I can access from stem to stern of a 93 Taurus wagon: plugs, wires, the whole exhaust system from the converter to the tail pipe. The engine still misses horribly and has almost no power; it climbs relatively flat slopes with the greatest of difficulty. I'm open to suggestions as to what I might have overlooked as far as getting this bird to run right, which it did before the resonator mounting flange rusted out and dropped the OEM exhaust system on the road a number of months ago. I'm thinking I may as well replace the O2 sensors; I've replaced everything else in the exhaust chain. But I'm not sure that would solve the problem. Thanks for the helpful suggestions (which someone's "proper testing" mantra is most emphatically NOT at this point, thank you).

[65comet]

3.0 or 3.8 engine, as the 3.8 was also available on wagons that year? When you say "from the converter", you are saying you replaced the cat, and not just beyond the cat to the backend, right? Just want to be clear you have a new catalytic converter.
You didn't say how many miles, but I'd guess for a 93 it is a ton, right?
Any check engine lights on?
Does it start right away and easily, or does it take a lot of cranking and you might have to give it a little pedal also to start?

[km2002]

Thank you for asking, 65comet. I was so frustrated by this, and I got such a short window to get on line and ask for help, that I left out those details.
3.0L engine. Cat converter, resonator, connecting pipe, muffler, tailpipe: All new as of last night. As I mentioned, I think I'm going to replace the O2 sensors just because; and strangely, the replacement converter has a hole on the top side for a third sensor, which my wagon does not use; so I need to get a plug for that (available locally). The odo shows >190K; if that's accurate after almost 20 years, I'd be surprised. Check engine light showed intermittently this morning; it's not flashing at me as if to say the engine will self-destruct in five seconds (my Jimmy was doing that). Started right away, but not real easily; didn't respond well when cold to trying to rev the engine. And while driving, had multiple incidents of feeling like the engine was on the verge of stalling, although it never did.

[shorod]

Do you have the means to check the diagnostic codes that are causing the check engine light (CEL) to illuminate?

Have you checked the compression in the cylinders? Do you have access to a vacuum gauge to check manifold vacuum? If you unplug the MAF sensor does the engine seem to run a bit better? If so, you may have a vacuum leak somewhere after the MAF that is causing most of your issue. Check things like where the intake air tube connects to the throttle body, the vacuum hoses for the DPFE (maybe when the exhaust work was done the hoses for the DPFE got reversed, damaged, or left off). Also carefully inspect the intake air tube itself, particularly in the flex area for cracks in the valleys.

-Rod

[km2002]

The vehicle is OBD-I at best, just triggering an idiot light; I'm not even sure there's a diagnostic connector on it. (It's a 93; OBDII wasn't mandated on US production vehicles until 96, so, no codes.) Unfortunately, no access to vacuum gauge (not immediately; I'd have to call some friends). Haven't gone looking for a MAF sensor; the Haynes manuals are sometimes suspect when it comes to such components; same w/DPFE. AFAIK, no hoses were removed during the installation of the exhaust system, although the extant O2 sensors were merely removed/reinstalled. These symptoms existed prior to the exhaust system replacement: It was suspected that a clogged converter was causing the symptoms; obviously, that is not the case.

[shorod]

Even though your car is a 1993 without OBD-II, it still stores diagnostic codes and there is a diagnostic connector. It will likely be located in the area of the passenger strut tower under the hood. It may be in a little cover with the letters "EEC" for Electronic Engine Control. There are ways to get the diagnostic code number without even having a scan tool.

-Rod

[km2002]

UPDATE: I replaced the O2 sensors today. The car runs a lot better than it did Friday, starts a lot better than it did Friday; but neither one as well as they used to. I still get the CHECK ENGINE light from time to time; oddly, it seems to happen more when coasting than when under load; in fact, loading up the engine (like trying to take a hill) usually gets rid of the light. I also replaced the EGR/pressure (or as the receipt put it, EGR/position) valve; unfortunately, both the tabs on the 20-yr-old electrical connector broke off when I tried to disconnect the unit; so it's holding on now by friction and prayer. (Any ideas how to secure the connector gratefully appreciated.) I'm left with swapping out the MAF sensor (1) if I can find it and (2) on the next paycheck when I can afford it. But the only thing I saw under the hood marked EEC (to be precise, EEC TEST) seemed to be (1) empty and (2) covering what appears to be an A/C port (which is a different problem altogether, as it seems I need to recharge my A/C). There was no connector that appeared to be electrical in any nature.

[shorod]

The pair of connectors you're looking for near the passenger strut tower will look like this:


As for securing the connector to the DPFE, you may be able to secure the connector body to the sensor using a couple of cable ties in an x-pattern.

-Rod