Loss of power

a while back our 98 blazer w/ 4.3 litre was suffering loss of power.  i read on one of the posts that a guy rodded out his converter. ours was rattling so we figured it was bad and peices were blocking the exhast.  I rodded mine out and no doubt the exhaust flow is better but we still have a consistent power issue.  Gas mileage has consistently been down a bit but not too bad. The only code we have is one that says the catylist is below the level that it should be (no shi$^$^).   Run and drives fine, the power loss is perplexing. Seems like the timing is consistelnly retarded. but no other codes. 
 
Any ideas? 

Replace the cat would fix the light.....

As for the loss of power, if you're thinking it's unrelated to the cat, it could be a fuel issue.  A fuel pressure test would be a good start, making sure to watch the pressure for a few minutes and make sure it does not drop considerably.

This is a good suggestion. I tried to replace the fuel filter a few time but it just won't come off. I've been soaking the threads with penetrating oil a few times for the past month and no luck. Any ideas on how to get that sucker off?

Have you read this tutorial?

Yea this would be helpful but my biggest problem right now is getting those treaded connections loose.

Yah the connections are really difficult to get off on your back and you dont really want to force it too much and break that nut off. If you tried numerous times it might be better just to take it to a garage and let them get coated in gas.

Personally, I had zero trouble getting the two nuts apart by using two wrenches. My issue came with getting the fuel lines out of the mounting bracket. Not to be insulting, but are you sure you're turning the nut the right direction?

WOW! turning right direction, that is pretty funny.  Yea I was, finally got a small pipe wrench out and trashed the nut  but it came off. I coated the threads with antiseaze compound when i put it back on.  Still drives the same way even after the new filter.  It runs very smooth and does not sputter even when giving it a lot of gas going up a hill. Just does not have power. Seems like the timing is retarded but still no code.

The only thing that I can think of that would cause retarded time, would be corrosion build up on the rotor or distributor cap. When was the last time the cap and/or rotor, wires, and sparkplugs replaced? This could be part of your powerloss and fuel economy situation. But I would think if something in those parts was bad that you would have sputtering or uneven idle.

As far as the fuel pressure testing, I am not sure exactly how to do that, but I believe you can get a gauge from an autoparts store and then hook it up to the test port on the back of the fuel rail (as mentioned in my tutorial listed above). I am not sure what the fuel pressure is supposed to be, but running a search for fuel pressure on the forum should get you some information on that. It could be an issue with the fuel pump, but without it sputtering (not having enough fuel) I would say its not the fuel pump (atleast not yet).

I would run the fuel pressure test and post back on the results of that and the last time you replaced any of the ingition parts (spark plugs, wires, distributor, rotor). Also if you did replace the spark plugs what kind did you use. I have heard from most people that our trucks only like the AcDelco Platinum plugs (thats what I replaced mine with, so far no problems (7k miles on them so far).

I would perform  throttle body cleaning  and a MAF cleaning, and also clean the egr valve. You may need an egr gasket, and a can of combustion cleaner for the egr and throttlebody, and sensor safe cleaner for the Maf sensor. If it doesnt fix the problem, it is still good maintenance. Also dont rule out the Map sensor, the specs for testing are here somewhere, i found it on a search a while back. Good luck.

So when is the power loss, when you get on the gas? Does it go away at higher RPM's? If that's the case, I would shoot for a simple tune-up. A bad plug is liable to do that.

It is my wifes car so I only drove it in on the country roads for the last test drive. Tonight I am going to drive it on the highway. She tells me it really craps out on the highway at 70 MPH and then ask for more power.  Will let you know tomorrow. 
 
For the short term the plugs were replaced at 120 K. It has 169K now.  I went with the ones they told me to use at the auto parts store which were platinum. I remember becuse they were wayyyy expensive but they said I was supposed to get 100K out of them. After I changed them I was glad I went with them becuase I am not anxious to do that again.
 
Car runs fine at any speed but when you push the accerator down it just does not have power. I does not sputter or hesitate of miss. Just accelerates way slower than it should. Other than that you wouldn't think there was anything wrong with it.  Higher RPM's it is still an issue.
 
Not sure on the plug wires or distributor. We bought it with 120 K and are up to 169 K.  I don't think I have done anything with the wires or distributor but Lenny I agree with you that you would expect  a miss or something. Idles smooth, motor purrs like a kitten. Just don't ask it go go up a hill or accelerate quickly. Ain't gona happen.
 
Again after the highway test tonight I will have more data.
 

Would anyone think that the o2 sensor is getting bad readings and sending signals to the ecm that could cause the fuel mixture to become too lean/rich? My last vehicle suffered tremendous power loss due to a faulty o2 sensor

Well unfortunately the hiway trip was inconclusive.  I drove about 35 miles last night.  Seemed fine at all speeds on the freeway. Would even slow down and give it gas and it shifted fine and never missed or stuttered or anything. Most of driving was between 65 and 75.  After I got off the freeway I was on back country roads and we have one big hill and I got on it going up that hill and it seemed ok so the test was a bust.  After I told my wife about this she was going out of her mind becuase of course most of whatever the hell is going on with this thing is happening when she drives it. it is her blazer.  Just going to have to wait for more info.  I think anything that would make a lean mixture is a good idea. I am going to pull a couple of plugs this weekend so see what they look like. If it is running lean it should show up there.  If that proves nothing then mayby ask the lovely to get off the crack.

LMFAO! Hopefully you get everything figured out. Good Luck!

I posted a few days ago on poor fuel economy and noted that acceleration was also poor. I have cleand all the sensors on the front end of the injection and the acceleration is significantly improved. None of the sensors looked particularly dirty and the MAP had a little gunk in it. Try cleaning all the sensors and changing the air filter.
David

Well we finally get to the problem.  A week back was driving and felt the loss of power. I decied that everything pointed to the fuel pump or a fuel pressure regulator. I figured the heck with it, it has 170K miles on it, I am just going to replace the fuel pump. Worse thing is I end up with a new fuel pump.  We plan on driving if a few more years any way. Two days later on the way to work the fuel pump completely took a shio&^&.  Had to tow it home at $107!!!  Dang I sure wish I could have put that money towards a fuel pump!  It's stitting in my garage and with the price of gas will probablly be there for awhile.  Put my wife in the 97 Aerostar with a 3.0, that gets 21 MPG.