Exhaust/fuel injection ????

[*HEAVY-CHEVY*]

I recently had to replace my cats. I talked to multiple exhaust shops and they all told me that I cannot cut out the cats and weld in 2 new ones or it would throw the same code within a few months and also cannot install anything other than shorty headers as far as aftermarket. So I ended up spending $600 that I didn't have to replace my pipes from the manifolds back to the muffler. Then within a month I have the same code coming up. I believe it is p0420 for egr. After having it closely monitored on a computer for fuel pressure and such they tell me something is wrong with my fuel injection and I am only getting single digits on one side and double what I should in the other! My 97 Tahoe with almost 160K runs better than any other one I have ever driven! So a couple questions:

1. Anyone had any issues installing high flow cats?
2. Anyone encountering problems with fuel injection? (example. lines clogging and cracking)
3. Do I need any special tuning after installing both long tube headers and highflow cats?

 

[fyremanpat]

I had the same problem. I replaced all 4 o2 sensors..still had it. I put the magnaflow hi flow cats on...still had it...I cleaned my MAF...problem solved. If it cant read air flow accurately its not gonna burn right in the cylinder. Get a can from the auto parts store and try that.. good luck

p.s. make sure its MAF sensor cleaner! anything else can leave a residue

 

[retorq]

You replaced exhaust because of an EGR code??

I don't see how a high flow cat will throw a code either ... sounds fishy.

 

[fyremanpat]

P0420- Catalyst System Efficiency Below Threshold (Bank 1)...can mean a number of things.

# An oxygen sensor is not reading (functioning) properly
# The engine coolant temperature sensor
is not working properly
# Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
# Retarded spark timing
# The oxygen sensors in front and behind the converter are reporting too similar of readings


* Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
* Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
* Inspect the downstream heated oxygen sensor (HO2), replace if necessary
* Replace the catalytic converter

---------- Post added at 11:46 AM ---------- Previous post was at 11:46 AM ----------

http://www.obd-codes.com/p0420

 

[*HEAVY-CHEVY*]

P0420- Catalyst System Efficiency Below Threshold (Bank 1)...can mean a number of things.

# An oxygen sensor is not reading (functioning) properly
# The engine coolant temperature sensor
is not working properly
# Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
# Retarded spark timing
# The oxygen sensors in front and behind the converter are reporting too similar of readings


* Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
* Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
* Inspect the downstream heated oxygen sensor (HO2), replace if necessary
* Replace the catalytic converter

---------- Post added at 11:46 AM ---------- Previous post was at 11:46 AM ----------

http://www.obd-codes.com/p0420

So i jumped ahead cause I was told my cats were bad. I left out the part where i went in and had a Cherry Bomb "Vortex" muffler put on and it was very quiet. I was told flat out that my cats were Burnt.I then put all new exhaust on including a cherry bomb "extreme" after replacing them I am getting the same code!
As For what "Fyremanpat" says I pulled the little screen out of the maf sensor when I first got the vehicle thinking I may be able to breath better. I guess there could be some residue in there from condensation or something?

---------- Post added at 08:25 PM ---------- Previous post was at 08:22 PM ----------

You replaced exhaust because of an EGR code??

I don't see how a high flow cat will throw a code either ... sounds fishy.

Well if you throw a high flow cat in and all of a sudden your o2 sensor is getting a much higher flow I believe it is going to think something is "fishy" too. Kind of like elimination the cats all together the o2 sensor is going to notice it.

 

[retorq]

I was thinking the single sensor in front of the cats like my TBI. Sorry carry on.

 

[slomo26]

I'm getting this code also (P0420). I drove around for about an hour with a scan tool plugged in trying to see what my 02 sensors were seeing. The readings from bank 1 sensor 1 were almost identical to Bank 2 sensor 1. The same with the two downstream sensors. Since Bank 1 and 2 are identical pretty much It makes me think its not the cat or the sensors. Am I on the right track? By the way its a 99 2 door Tahoe. Thanks for any help.

 

[bowtiefreak]

I have high flow magnaflow cats with no problem. Try cleaning the MAF and the EGR.

 

[slomo26]

Ill give that a shot. Thanks

 

[gmtech]

The main thing is to not spray anything right on the wires do like a light mist and take a small pick and lightly scrap the wires to get anything off then lightly spray some brake cleaner on them and let dry and that should do the job