I need help with a problem. I have an 01 Monte Pace Car Limited Edition that I aquired recently. It is in pretty good shape.(112K) Had to rebuild the tranny, installed K & N, did the U-bend delete. Lately I have have notied a problem. During slow to normal acceleration I do not notice much difference, but during a harder acceleration, like entering a freeway ramp or passing, there is the initial power surge from the engine then the power drops off significantly, but if I ease off the accelator a little the power picks up again, then if I try to accelorate more it bogs again. Has anyone else experienced this problem. Does this sound like a catalytic converter problem.

 

it does but first i have to say did you do a tune up. the reson why i ask some times doing a tune up clears the problem. if the problem comes back after the tune up it is the cat. the tune up is cheaper and it will rule out that part of it. because it is usually one or the other what i mean the lack of a proper tune vehicle it will lead to a bad cat. there is a problem with our cats only last between 90k to 120k. the cat should be around 120 to 230 but it is a estemit

 

i also forgot to say get your car scaned at a shop you trust so you will know what is really going on. because some times there will be a error code if there is a problem with the cat. there is some thing else going on check it out also the check engine light the light it self might be taken out. so have the computer checked so you dont have to worrie about trying to throw parts at it to try to fix the problem

 

Could be a clogged cat, could be the fuel system is plugged up and isn't able to keep up with the higher demands.

I remember when my fuel pump died on my monte, not too long after my engine swap- it would drive around town just fine. After a certain point, the more you got into the, the slower it would feel- and if you really got into it, it would almost die.

Ran a scan, and driving around, the fuel trims were REALLY high (almost pegged) driving around, and if you got into it, they would max out and the engine would go lean. Put a fuel pressure gauge on the rail, and it was sitting around 25-35 psi. Put in a new pump and it ran great.


I agree- just saying it sounds like it could be one thing or another and replacing it isn't the best plan. You need to hook up a scan tool to see what's going on when it happens with the engine sensors- and if you still suspect the cat after that, you could use one of those remote temperature guns to read before/after cat temps after driving around getting on it.

 

In my experience a bad cat usually wont show up on a normal OBD 2 scan. When mine went out I got a pressure test performed before and after the cat and thats how they realized it was bad. Cost me $15. How is your gas mileage?

 

actually it can but wont throw a check engin light till it almost gets to the point where every thing is effected. on the over the counter obdii scan tool wont check what is data logged in the computer of the car. the one that i have is the scan tool that is about 4k that reads gm ford and the other types. it also reads the data log on what is going on when it is running as in is it going lean for a air flow to a fuel problem. to every thing else but it is hard to know what is going on with out that heavy type of scanner

 

Obviously there isn't any particular sensor that will show you the cat is bad, however- I absolutely hate just shotgun replacing parts unless its a common bad spot (ie the turn signal stalk on the 5th gens making the brake lights go wacky). That's what I mean- you're better off scanning it, seeing what all the sensors are doing- that will help narrow the problem down- and if all of that is showing up pretty clean, then test the cat.

 

Thanks for all the suggestions for my problem. First let me appologize for jumping right in with a problem, as with most I had been a member before (boilermaker), then, well, as most know it was tough getting on. Anyway, it is nice to be back with the Monte family. Now back to the problem at hand. The problem just recently started. As to a tune up, I do not know when the last was done (if ever) as I bought it used. I recently had it scanned at the Chevy dealer trying to solve another issue, temp gauge quit, A/C comp. quit. Another shop said it was electrical and would track it down for $99 an hr. Took it to local dealership, they scanned it, thermostat stuck open, cleared codes, everything worked. Replaced the T-stat. Who would've thunk it. As to the fuel system, I thought about that after I posted, that to is probably something that has never been addressed either. Perhaps a tune up and fuel filter will solve the problem. Hope so. But if it turns out to be the cat, any suggestions on a good downpipe/cat replacement, other than OEM, preferably stainless that is legal. Most that you find on the net say "for off road use only", does anyone take their Monte offroad? (sarcasm). Again, thanks for all suggestions. And yes, as soon as I can remember how, I will post pics of the 01 and the 04

 

If it's a 3800- I know zzp makes downpipes with a cat.

 

ive had this problem before and it bugged the hell out of me. i did a tune up, got an off road DP and a few other things everyone on here told me to do. well turned out it was a clogged EGR valve, somthing about when i was a full throtle (and sometimes just gassing it a bit) it wasnt closing all the way. now im not saying thats your problem but defiantly somthing to have checked out. i just had a guy at auto zone do one of those seafoam things. i dont know how that stuff works so i had them do it.