Hi I have an 01monte ss with the 3.8l in it. 79,000 miles on it. I have a problem I can't seem to figure out. The car has no power when you step down on the gas, if you go easy it will go fine, but when you get on it, it will bog down, not rev up like it should. I have put a new fuel pump in it, two fuel filters, fuel pressure regulator, plugs and wires.
The reason for fuel pump and pressure regulator and filters was it would idle at 55 psi, when you hit the gas it would drop to 14 psi.
Plugs and wires in it because it got and error code for multiple misfires and misfire on cylinder 3
Now I ran codes again I got oil pressure switch malfunction. Does anyone have a idea what is wrong with it? I have been told the cat is plugged, but that would not explain the low fuel pressure. I do not know which way to go and am tired of dumping money in it trying to figure it out.

 

Have your catalytic conveter inspected for blockage.

 

Sound's allot like what mine did, last thing I replaced was the cat. It was about the 88,000 mile mark when it got worse. I temperature tested the cat and it was showed good but I had a feeling it was bad. Bought one from zz performance and took it to the local muffler shop and they asked me why I was changing it with that few miles on it. Anyway, got it done, stepped on it hard and WOW. All my power was back.

 

Ok I took off the cat tonight and put a piece of pipe in its place and it doesn't run any better, any other suggestions?

 

I assume you have no other codes other then a oil pressure switch code? And I assume you are not low on oil (normally when the oil pressure switch/sending unit fail, it also begins leaking oil)? If you are not low on oil and you pulled the cat out ruling that out of the equation, have you checked for any other blockage in the exhaust?

Also, have you checked the air filter, made sure that is pretty clean? And no surprise visitors living in the air box?

The 3.8's have had a history of the MAF sensor causing weird problems. 03SSLE has the information to properly test the MAF and it's wiring harness using a volt meter. A "poor man's" test is to disconnect the MAF while the car is off. Then start the car and see if the problems persist. If it does not persist, it does not mean 100% it's the MAF sensor, but now you know it's not an intake or exhaust issue. But it would suggest it to be the MAF or something the MAF has some control over. You could attempt using MAF cleaner as you next course of action.

 

No other codes, oil is full, exhaust is clean. Air filter is new and the air box and pipe are clean. I unplugged the MAF sensor then started the car, it still acted the same. The only code I get is the oil sensor malfunction. I unplugged each injector while it was running to see if one was not working, each one the engine bogged down when it was unplugged. The engine is running very rich. I took the MAF sensor out and cleaned it with MAF spray, still the same.

 

What are ALL the codes you had or still have?? Did you cut the cat off and weld in a straight pipe?? Have you tried flooring it and see what codes it activates then?? Does your engine light flash if you floor it for more an minute?? Sometimes NOT all problems will throw a code, could be your EGR valve and or EGR pipe clogged. Just my 3 cents.

 

The next shot in the dark I have is a failure on the upstream O2 sensor (that is the one before the cat in the rear exhaust manifold). That O2 sensor does impact fueling and might be failing but not throwing a code.

Out of curiosity, what is the actual code you are getting about the oil pressure switch?

 

Work, all the codes I have gotten are multiple engine misfire, cylinder 3 misfire, and the oil pressure switch malfunction. I have removed the cat and put a straight pipe on it. If I floor it, the highest I can get it to rev is 2300-2400 rpm, it will not rev any higher just cuts out. If I go easy on the gas I can get it up to 3900 rpm, but it acts like I am hitting a rev limiter and keeps cutting out, I have run it down the road pulling steep hills and long straight stretches for for 5 miles with it floored, and have floored it sitting in the parking lot to see if I could get anything else to pop up, the only code is the oil pressure switch, no check engine light since the misfire on cylinder 3 which came up first, new plugs and wires were in stalled and the check engine light hasn't come on since. I plan on checking out the egr valve tomorrow.

Manic I do believe the code I get for the oil pressure switch is P1189, the reader is in the shop where I am working on the car. I will check the O2 sensor tomorrow as well, thank you all for the help

 

Can I just ask if you removed the cat and not the resonator by accident?

if you did remove the cat with a straight pipe you'd most likely have the P0420 code.