2002 OHV 3.0L Lack of power, stiff brake pedal

[Ruley73]

This car has me stumped. I replaced the ignition coil a week ago (it was bad) and all was well. So fast forward to today and my sister-in-law is stranded on the interstate. Turns out there was a hole burned into the plastic plenum (see picture below. I put a leather glove over the hole to get her home. I repaired it with some QuikSteel epoxy and let it fully cure before starting the engine. Now, the engine won't run very well and the brake pedal is very stiff, almost like the brake booster is bad.

intakehole.jpg

The engine won't rev higher than 3600 RPM (not hitting rev-limiter) and idles erratically (vacuum leak? - can't find one). It has an extreme lack of power going down the road and only goes about 50 mph going downhill. No SES light or codes.

This one has me stumped and I don't know where to start. Any help is appreciated.

[snshddog]

Sounds like it could be a plugged exhaust. This would cause the hole in the intake and the lack of power. The coil having gone bad could load the cat full of fuel which will melt it after a while if the coil went flakey for a time before it quit. Unbolt the exhaust before the cat and see if it has the power back. This would reduce power brakes too, if the engine cant blow out then it cant create the vacume for booster

[Ruley73]

Originally Posted by snshddog

Sounds like it could be a plugged exhaust. This would cause the hole in the intake and the lack of power. The coil having gone bad could load the cat full of fuel which will melt it after a while if the coil went flakey for a time before it quit. Unbolt the exhaust before the cat and see if it has the power back. This would reduce power brakes too, if the engine cant blow out then it cant create the vacume for booster

I thought about that after I made the post and that's exactly what I was thinking. The coil's been bad for at least 6 months and she's been driving it at least 60 miles per day.

This all adds up and makes perfect sense.

[Scrapper]

yes it does sound like booster if you got rock hard peadal? try unpluging it from booster and see if you still have good vaccum going into booster? but i think your on rite path on booster.

[Ruley73]

Well, I took it to a shop and they had a way of testing all three of the catalytic converters for free. They confirmed that the rear main (after the Y) catalytic converter is plugged. I thought that would be the cheapest one to replace, but they quoted me $650 to replace it. Seems a bit high to me even if they are charging us twice the price of the part. I was thinking more like $450-$500.

[Ruley73]

The shop replaced the catalytic converter and the car drives much better now. They also repaired a vacuum line going to the brake booster. Now we have another issue. I am getting codes P0152, P1151 and P1152. These all seem to point to a bad O2 sensor (bank 2 sensor 1). Anything else I should try before replacing that O2 sensor?

Also any tips on replacing that sensor?. It's the one in the front manifold. Things look pretty tight in there so it doesn't look easy. The things that appear to be in the way the most are the A/C lines and the cooling fan.

[Ruley73]

Anyone?

[Ruley73]

Well, I didn't get any responses so I figured it out for myself. I figured I'd post here for others to see in the future.

The car is a 2002 Ford Taurus with the Vulcan pushrod OHV 3.0L engine.

The O2 sensor in the front exhaust manifold is pretty much impossible to change from the top. So, you need to change it from the bottom.

To do that you must first remove the black splash shield that's in the way. There are eight 5.5mm hex-head screws and three 8mm hex-head screws holding it in place. Once the shield is removed, you have just enough room to work with. If you have really big hands, you may have trouble squeezing between the radiator and the front subframe crossmember. It took under an hour for me from start to finish.

I used a crows foot oxygen sensor tool (for 7/8" hex O2 sensors, accepts a 3/8" drive ratchet) and a short 3/8" drive ratchet to remove the sensor.

Also, I used a Denso O2 sensor for replacement. I've had bad luck with the Bosch O2 sensors and strongly recommend NOT using them. I'd use either NTK/NGK, or Denso branded O2 sensors. Of course an OEM-replacement Motorcraft O2 sensor from a dealership is always a sure bet too.