Catalytic Converter

Start with simple, probably needed anyway things first: fuel filter plugs

Your code and running problem could be 2 different things. If the car has alot of miles it could be just a worn out cat turning on the light. get the thing running right first, then mess with the cat. A plugged cat can cause power loss but not likely a hessitation from a stop. If its been a while I would just start with a tune up including fuel filter.

yes

it will also cause engine damage

hurc ast

I retired from this business in 86 about when they started going nuts with emission requirements. After dealing with these shops I figured I'll take a stab at it myself so I bought the OBDII scanner and am learning to use the data supplied by the onboard computer.

I've been fighting this problem for a month. The car has been to the shop 3 times and still has problems with dying at stop signs, hesitation, and what feels like a miss at any speed hot or cold, and sometimes shudders when coming to a stop. The car 96 Sable 3.0 single overhead cam with 61000 miles. The parts I have replaced are as follows: plugs wires maf tps egr pcv fuel pressure ok vacuum ok one upstream o2 sensor (bank 2) today which is operating in specs now. According to the scanner the o2 voltage on the sensors are almost running together indicating a bad cat on the #2 bank and the #1 is starting to look bad. Lately it put out the old rotten egg smell which usually indicates rich fuel. The #2 bank was rich and the new sensor took care of that. Since both cats are looking bad I can't hardly belive the fuel injectors are at fault. I haven't been using oil or water which would foul the cats. Any ideas would be appreciated. Thanks

My old Dodge (DiamondStar, ugh) with EGR stuck open exhibited identical driveability problems. You replaced the valve, but are you certain that is working correctly? On my Dodge, there was an EGR controller that was "tuned" to work with a specific EGR valve. They were supposed to be replaced as a pair. I suppose the new EGR could also be stuck open for some reason. Driving around with an open EGR can quickly plug a cat.

Rodney

I didnt see fuel filter in that list, also clean the throttle bore and clean or replace the IAC. Check the voltage on the rear O2 with it warmed up good and at a high idle. Your bad upstream O2 could have fouled the cat. The cat code will not make it run bad.

And, if the cat is plugged a good muffler shop can test it. Then while your there have them replace it if so.......A plugged cat will act like its running out of gas, the harder you push it the slower it wants to go. Dont forget that fuel filter, cheap insurance.

Forgot fuel filter was 1st also new gas cap. sometime it acts like theres no fuel then she takes off.

Throttle body was cleaned also, forgetting things must be getting late.

if you can find a place to tap into the exhaust ahead of the cat (yank the O2 sensor if nothing else) and install a pressure gauge you can tell real fast if the cat is plugged. Should have only a couple pounds of back-pressure.

Pulled o2 sensor installed 0-15 psi gauge got less than 1 psi backpressure. I did install a new ect sensor and seems to be running better. I need to find a test procedure for the cam sensor.

Did you ever change that fuel filter?

Also, I've seen ALOT of 3.0l 12valve Tauruses come in with BROKEN cam sensors, they run fine, just the CEL comes on. You didnt put those Bosh platnium plugs in it did you? Those things seems to cause alot of problems.

I used autolites with a new fuel filter first thing I did. I'm looking closely at the DPFE sensor. I see a lot of postings about how this can cause a lot of my symptoms. I need to get a vacuum pump before I can test.

Just some tips I gleaned from alldata for a 2000 DOHC 3.0 Duratec, my guess is that they are similar for your 1996 SOHC 3.0.

Is the fuel pressure within spec? Too high might cause a rich condition.

No exhaust leaks from the manifolds to the muffler?

Is the engine running too hot? Coolant level is OK?

Catalytic converter chemically inactive?

That last one was listed but can't say I know how a cat becomes "chemically inactive".

Fuel pressure good, no exhaust leaks, engine runs normal temp, converters according to my scan tool are working satisfactory with correct inlet and outlet temps, I'm leaning toward a bad DPFE which has my symptoms. The backfire may because the computer is trying to lean it out. I just bought a vacuum pump to test the DPFE.

DPFE is a very common failure on the Fords. A lot of the 2001-2002 and some 2000 models Fords had a recall. I had mine done at the dealer in Nov 2002.

It failed again two years later and I replaced it for twenty bucks or so. I scanned the computer and got P0401 after the MIL went on. It was on for a little while and I got tired of procrastinating going through the pinpoint tests so I just gambled the money on a replacement. Paid off this time.

Coincidentally it failed the last time on the same day I got the car inspected at the state inspection station. Wonder if their equipment did it.

Well I just finished testing the DPFE checks out fine. Even with the EGR plugged off I still get a stumble at about 50.

I have a STRONG suspicion you have dirty injectors. Find a shop with a "motorvac" system and give it a go.

The problems I'm having are intermitant would the injectors act up all the time? I idles just fine. If I snap the throttle it bogs then backfires through the intake but not always. I'm going to do a compression test this weekend.