Clogged convertor?

I think the Cat Cov may be clogged, not 100% sure though.

Is there any way to know for sure or to test it?

Yesterday I was in Southern Ohio in the hills. As I was going up hills my speed would go down. We come to one and I had to FLOOR the car to maintain 45 MPH...

I know my N/A car isnt fast or furious, but this is ridiculous...

There is a test that involves some special tooling (basically a pressure gauge) that requires drilling a small hole in the pipe ahead of the Cat and pressures are measured cold and hot and at speed to determine if the cat is blocked.
The hole is then filled with a self tapping screw.
Usually the Cat's fail by not allowing airflow when hot and trying to accelerate under a load or at highway speeds. Which sounds like your symptoms.
BTW, the NA 3800 is a pretty impressive motor, lot's of torque and acceleration for a naturally aspirated motor.
I still prefer the SC, now that I own one. But before having an SC 3800 I was very impressed with the 3800. In general an excellent powerplant and most recently I lost my SC belt and drove the car for several days without the SC and it ran very good.
Now with the smaller pulley and some tuning it is most impressive for a mildly modified V6 engine.

Ya Im going to take it out to a garage tomorrow and ask them about it.

I will probably have them just remove it and put a pipe on it. They will do it Probably for free or like $25 if I give them the cat converter...

I was recently told that the CAT's aren't bringing the good money to the shops anymore. I don't know how true that is. The guy that told me that did some stainless welding for me on my exhaust and i was trying to barter with him for my old CAT and he wasn't interested in dropping his fee for the Cat.

If you attach a vacuum gauge to the motor. You should see about 20" at idle fully warmed up in Park. Run the engine at about 2500 rpm for about 15 seconds. If vacuum drops during this period and does not increase when you close the throttle, you're almost certainly looking at a restricted exhaust.

Thanks Larry,
I always forget just how useful a simple vacuum gauge can be for troubleshooting and diagnosing engine problems.

One way to test catalytic converter is to put car in neutral and rev the engine to the 3-4k range (when warm). According to GM:

"If the engine freely accelerates to higher RPM in Neutral, you can assume that the engine and the exhaust system are normal."

If there is any lag in getting into the upper RPMs, you might have a clogged cat.

If it were mine, I'd check transmission fluid level and color/smell immediately. Low or burnt fluid, or a failing trans, can cause the symptoms you're reporting.

^ I will check that right now. Ive been intending on changing the trans fluid/filter but havent done it yet.

Ok, I havent done a thing with this car due to lack of money.

I thought about the transmission issue. While it may be possible, I still wonder. The car still doesnt run as smoothly as I think it should when in park or neutral.

Ryan, how long have you had an 04 Impala engine in your 95?

AA wrote:

One way to test catalytic converter is to put car in neutral and rev the engine to the 3-4k range (when warm). According to GM:

"If the engine freely accelerates to higher RPM in Neutral, you can assume that the engine and the exhaust system are normal."

If there is any lag in getting into the upper RPMs, you might have a clogged cat.

If it were mine, I'd check transmission fluid level and color/smell immediately. Low or burnt fluid, or a failing trans, can cause the symptoms you're reporting.

Ok I tried this today.

The car in park will go up to about 3,500 RPM and sputter like... It will go upto 4K but it sputters throughout.

So that would signal clogged cat?

Not necessarily.
Have you checked vacuum readings as previously mentioned.?
Have you had a CASE Learn procedure done since swapping crankshaft position sensors.?

Ryan from Ohio wrote:

AA wrote:

One way to test catalytic converter is to put car in neutral and rev the engine to the 3-4k range (when warm). According to GM:

"If the engine freely accelerates to higher RPM in Neutral, you can assume that the engine and the exhaust system are normal."

If there is any lag in getting into the upper RPMs, you might have a clogged cat.

If it were mine, I'd check transmission fluid level and color/smell immediately. Low or burnt fluid, or a failing trans, can cause the symptoms you're reporting.

Ok I tried this today.

The car in park will go up to about 3,500 RPM and sputter like... It will go upto 4K but it sputters throughout.

So that would signal clogged cat?

No, our cars have a rev limiter in Park/Neutral. It won't rev and that is normal. Drive the car.

The purpose of the test is to see if it revs up quickly. If it does, your cat is not likely an issue. If it revs up slowly or with labor before it hits the limiter, you could have an issue.

sounds like PCM mismatch. Need PCM from donor car and pinout of new PCM and old PCM - tehn use a pick to remove/replace pins in harness. there will be several but not all to move. IDK if the cams in the S III differ from those in the S I but if so then even matching all the sensors won't work, IIRC the fuel trim and timing will be off if you do that.

Albertj

Ryan, do you have a 3" DP or headers ? I still have the 321 stainless 3" test pipe and reducer (to 2.5") that came with the headers I got.

Jason wrote:

Ryan, do you have a 3" DP or headers ? I still have the 321 stainless 3" test pipe and reducer (to 2.5") that came with the headers I got.

Its the stock stuff.

Just to be clear the 1995 Rivi had a Series 2 N/A motor in it. The S/C 95's were Series 1

The entire intake manifold, throttle body is from the 95' rivi.

The new motor, I had to swap out injectors, sensors, oil filter modular piece and the water pump modular setup and alternator stuff.

everything else is from the original 95 rivi. Just used the short block basically.

got it.