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I recently bought a new (to me) 05 Impala that, as suggested in the title, was a police car. It had 155.6K miles on it, asking $3K cash. Since my Regal had blown its headgasket and had a myriad of problems wrong with it, I leaped on the chance.
Other than a few minor repairs I’ve been happy with the purchase. New front speakers, a cupholder, radio to listen to my weird music. However my first repair has popped up after 2-2 1/2 months of owning the car… the dreaded P0420 code.
Since a number of things can cause this, I’m asking some experienced guys with GM cars, namely the ones with 3800s, what are some things to look at. I do have some concerns and over the following week will try to get a better look at the problem.
Turkey Day I will be able to hook up a scan tool and have a chance to look at the O2 sensor data and have a rough idea what to look for, and plan on inducing a lean condition to see what happens. But I have some concerns.
The rubber in the radiator strut mounts allows for a fair amount of play in this car, so much that I actually feel it in the car as it accelerates or brake, or even turn. I’m concerned I have an exhaust leak due to the moving engine (and therefore, exhaust pipes) but havn’t had a chance to go climbing underneath the car. I also have no idea on how to tell if actually DO have an exhaust leak somewhere. Other concerns is if the cat is just barely below the overly sensitive threshold commonly reported on this car, how can I tell via sensor data? Another concern, the downstream O2 sensor around the nut portion is BLACK. Yeah, not kidding. Having sold auto parts for 4 years at Advance, I’ve seen my fair share of old Sensors, this does not look normal. I’ll have to get closer to make sure its not a trick of the light, but if it isn’t doesnt look good for the sensor. I also of course plan to hit it with my palm and check for broken pieces in the cat, but seems unlikely as it accelerates just fine and gas milage is pretty decent for city driving, I get about 170-200 miles on 8 gallons of gas.
Basicly I want to cover all the bases before actually trying to fix the problem. Thats just my nature. Look at all angles and then act.
PS: How can I tell if I have the HD or normal 4T65 transmission?
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Ok, as I said I’ve managed to plug up my dads scan tool and take a look at the O2 sensor data and its not good.
Both front and back sensors are switching rather rapidly and the downstream seems to mirror the front. Not a good sign. I havn’t crawled under the car yet but got as close to the exhaust system as I could to see if I could hear an exhaust leak and it does sound like I have one, but it might be the resonator. I havn’t been able to actually get under the car yet.
shame, $200 repair… ugh. I don’t have emissions testing but I’d like to have the problem solved and not have to worry about regularly checking the codes to make sure any more serious problems have manifested.
[quote=”Sovek” post=119909]Yeah, Having worked in a parts store I heard similar stories of the Bosch plugs being absolute junk in GM engines. Same goes for Autolite copper plugs, Think I had someone change the plugs with copper on one of those GM engines, came back in after the plugs fouled demanding a warranty refund.
Speaking of Evap canister, Fuel pump shuts off when unless I baby it when refueling. Best way to go about fixing this? No EVAP codes, just that minor annoyance. I can see the main line running from the gas tank, but not the one leading to the solenoid. weird.[/quote]
actually…. a common practice when tuning the 3800 is to switch to Autolite copper plugs a heat range cooler, the reason is when people up the boost with a turbo or smaller supercharger pullies the air fuel mixture becomes much easier to ignute, I think too easily, I think switching to the cooler autolite coppers reduces spark knock and allows higher boost levels, otherwise it is recommended to stay with AC Delco buy the manufacturers and even the guys tuning the engines will say the same thing, stock engine with few modifications stay with AC Delco, engines with higher boost smaller blower pullies go with a heat range cooler autolite copper.
and I agree with JTF, fuel canister lines are probably clogged or kinked if you are having issues refueling, I think sometimes even if there is issues with the canister it will act up.
So with a downstream O2 sensor mimicking the upstream, I probably should look at replacing the cat, correct?
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