exhaust/fuel injection???

[*HEAVY-CHEVY*]

yep! its crazy how the little things cause such a big affect

Check engine light is back on after 1 week.

 

[fyremanpat]

if its the same code again then chances are its ur o2 sensor...its weird that it went this long without coming on

 

[*HEAVY-CHEVY*]

if its the same code again then chances are its ur o2 sensor...its weird that it went this long without coming on

So all 4 need to be replaced? Is there any way to test them?

 

[fyremanpat]

You gotta find out whats causing it to run weird and cause it throw this code...if you go to most exhaust shops they can test your cats
http://www.obd-codes.com/p0420

 

[hapyspaz]

Use premium gas and see if the light goes off after a bit. If so, your O2 sensors are getting too sensitive and need to be replaced. Only way to determine if one or all are acting up is to hook up to a scanner and watch the readings of the sensors while the engine is running.

 

[*HEAVY-CHEVY*]

You gotta find out whats causing it to run weird and cause it throw this code...if you go to most exhaust shops they can test your cats
http://www.obd-codes.com/p0420

Well that's the thing. My tahoe runs like a dream aside from getting a little less that preferred gas mileage and when I did have it looked at by the exhaust shops they said my cats were burnt. If you crawl under and look they are blue! The thing is they were only about 3 weeks old when I got this code so they sent me to their full service shop. That is where they hooked it up to the computer and monitored the sensors and fuel pressure and came to the conclusion of faulty fuel injection.

 

[hapyspaz]

Test the EGR since you keep getting told that is an issue.
Put vacuum to it at idle. If the engine dies or stumbles, clean or replace EGR.

We already know you have someone telling you your fuel pressure is whacked. Get the fuel pressure regulator changed out. Fuel Pressure Regulator. I would recommend to just get Fuel Injector with a Gasket Set.

Fist thing I would do is have a shop look at a few things. Misfire history, what and how many times have which cylinders misfired. How do the O2 sensor readings look? Check the timing (with scanner), mine was out 6 degrees but it still ran good. If the shop that replaced your cats is affiliated with the shop that is telling you your cats are bad, make them replace them again under warranty. Who knows, they may have screwed up on install.

With the only drivability issue being less than perfect gas mileage; and a code that is a "generic" code, it is very hard to nail down the issue without more informaion.

 

[bowtiefreak]

I'd look at the O2 sensors.

 

[kope]

you can bench test your o2 sensors. its really easy all you need are a Digital Mutilmeter to quickly measures OHMS and a torch of some sort. just google o2 bench test theres a good writeup somewhere out there i used.