'03 3800, sluggish

[bigj-dog]

I've got an '03 Impala with a 3800, 104k. Starts ok and runs ok, but doesn't have as much power as it should. If I start out from a stop and floor it, it'll takes off ok and it'll rev up to about 3800rpm, then just sit there, if you let off, it'll shift to 2nd and then you can ease it up to highway speed. If you drive normally, it's not real bad, just feels like it's gutless. When it's floored and hanging around 3800 or so, the CES flashes and the code present is misfire in cylinder number 2. A couple of minutes after you let off, the CES goes out and there is no code stored. Initially, I thought it was the fuel pump/filter, because it seemed as if it was running out of fuel. Put in a new fuel filter, no change, checked fuel pressure, 45 running, 55 w/regulator line pulled off, 45 with return line pinched off. Those numbers seem to be in line with the requirements. Now I'm leaning towards the cat being plugged, as it seems to be a somewhat common problem. If anyone else has any ideas, I'd appreciate it. Thanks

[maxwedge]

Are the plugs and wires original if so they must go, the cat can be tested using a pressure gage in the ft o2 port, shouldn't be over 1.5 psi under load. BTW. I would put a 20oz bottle of Chevron Techron in there to clean up the injectors.

[impalalover]

Originally Posted by maxwedge

Are the plugs and wires original if so they must go, the cat can be tested using a pressure gage in the ft o2 port, shouldn't be over 1.5 psi under load. BTW. I would put a 20oz bottle of Chevron Techron in there to clean up the injectors.

my 2005 with the 3400 seems to be doing the same,but runs excellent,has 70 000km's,do you think a new set of plugs or wires or both will make her feel more responsive,i have noticed some pinging in the last few weeks also,even with high octane fuel,i thought the g.m wires and plugs were good up to 100-150 000kms before you have to change them,i change my oil every 5000 km's and use castrol 5w30,have any suggestions,she isn't throwing any engine codes either,what would be a good affordable plug to put in her

[maxwedge]

You do not need high test, waste of money, second at the that mileage under normal circumstances the plugs and wires are not an issue. The pinging is something that is abnormal and probably not the traditional low octane fuel " ping." Tough to tell from here what your symptoms really are, try some injector cleaner, except for the noise, sounds like there is no driveability problem.

[bigj-dog]

I couldn't figure out how to check the pressure at the O2 sensor, so I just disconnected the pipe in front of the converter and, although it was a little loud, took it out on the open road, it had gobs of extra power, shifted and ran just perfect. I'll be installing a new cat friday after work. BTW, we installed plugs and wires at about 90k and Techron goes in every other oil change. It's a must for GM vehicles as far as I'm concerned. Haven't had an injector problem since I started using it 6 or so years ago. I'll post back as soon as I know if the solution was found. Impalalover, I'd try the Techron, but I did have a '01 Sonoma that the cat progressively plugged itself and left it powerless by 75,000 miles. Seriously powerless, couldn't even make it up my driveway. New cat and it was a new truck. The easiest way for me to tell that it was on its way out, was to pay attention to the pickup when it was cold (not outside, the engine temperatures) and then again after it warmed up. It didn't take long and the difference was VERY noticeable.

[impalalover]

Originally Posted by bigj-dog

I couldn't figure out how to check the pressure at the O2 sensor, so I just disconnected the pipe in front of the converter and, although it was a little loud, took it out on the open road, it had gobs of extra power, shifted and ran just perfect. I'll be installing a new cat friday after work. BTW, we installed plugs and wires at about 90k and Techron goes in every other oil change. It's a must for GM vehicles as far as I'm concerned. Haven't had an injector problem since I started using it 6 or so years ago. I'll post back as soon as I know if the solution was found. Impalalover, I'd try the Techron, but I did have a '01 Sonoma that the cat progressively plugged itself and left it powerless by 75,000 miles. Seriously powerless, couldn't even make it up my driveway. New cat and it was a new truck. The easiest way for me to tell that it was on its way out, was to pay attention to the pickup when it was cold (not outside, the engine temperatures) and then again after it warmed up. It didn't take long and the difference was VERY noticeable.

yes i notice that in the mornings or on cool days my car is perfect,when it is hot outside she seems to have a power loss and it seems like i am driving with my foot on the brake or like a sticky caliper,so it might be the cat??/,but should'nt she throw a code to let you know something is wrong with the cat,or what do i do,go to the dealor and get them to scan her??,thanks

[bigj-dog]

If the cat is bad, it'll get worse as the engine warms up, outside temperature shouldn't have much to do with it, but if it runs better when the engine is cold/cool, the cat is the first place i'd look. As far as the CES light goes, the one I'm working on, according to the primary driver, has been losing power slowly for quite a while, and just last week was the first time it threw a code. And that code was just a cylinder 2 misfire. If you went to a dealer, they may have the capability to check some of the sensor's information or something else that could give you more information on the cat's health, but I don't know for sure. If you want to know for sure, just unhook it and give it a try. Try your 0-60 time both w/ and w/o the cat. If you just drive it with the exhaust open, you'll think it has more power because it'll sound like it does. With the one I'm working on, there was a definite plateau in the acceleration, ie the tach wouldn't go over 3800 if you were hammering on it, so with the cat unhooked, all we had to do was watch the tach and it blew past the magic number and viola, (hopefully anyway), we have found the problem.

[maxwedge]

Hit the cat see if it rattles internally is one way to see if is bad, there is another way, but is more complex and requires a high line scanner. Partally clogged cats are a little tough to diagnose.

[impalalover]

Originally Posted by maxwedge

Hit the cat see if it rattles internally is one way to see if is bad, there is another way, but is more complex and requires a high line scanner. Partally clogged cats are a little tough to diagnose.

i just did that not more then 10 mins ago,it sounds solid and seems to be working fine today but ijust filled here up with high octane supreme fuel,replaced my plugs with original replacement plugs but still have a pinging,have no idea why,checked my oil to see if i may be haveing intake gasket problems and my temp hand is normal so i don't know why she pings

[impalalover]

Originally Posted by impalalover

i just did that not more then 10 mins ago,it sounds solid and seems to be working fine today but ijust filled here up with high octane supreme fuel,replaced my plugs with original replacement plugs but still have a pinging,have no idea why,checked my oil to see if i may be haveing intake gasket problems and my temp hand is normal so i don't know why she pings

max wedge,is there anything thqat can be done with the stock airbox to get more air flow,there is a guy on here who said he took out the airbox and cut off the front by the pcm??,will that make a difference to power and fuel savings do you think

[maxwedge]

There may be some slight additional airflow at the high rpm end, but very little and with a stock engine no real advantage, peoples expectations and the increased engine sound can throw off real world results.

[bigj-dog]

Installed a new Catco cat yesterday morning along with new O2 sensors, everything is back to normal. Old cat had liquid sloshing around in it once I got it off, usually not a good sign of it's good health.

[HeMi101]

Originally Posted by impalalover

max wedge,is there anything thqat can be done with the stock airbox to get more air flow,there is a guy on here who said he took out the airbox and cut off the front by the pcm??,will that make a difference to power and fuel savings do you think

I Gutted my airbox and added in a K&N Drop in FIlter. the gutted box it self doesn't proove much in most of the range, but helps in high rpms a little when you floor it. I just really love the sound, didn't expect much power change from it. But does feel more responsive once i got the K&N but again very little, but noticable.