Need Assistance from someone who is familiar with emissions equipment.

[4g63lover]

I was driving the Galant today for her once a week drive and I gave her a little pull in second coming out of a stoplight. As I shifted into third, the SES came on. I went to Advanced Auto to get the code checked and they came up with Idle Air Control Malfunction (I knew I was throwing this code) and Catalyst Efficiency. Now, only thing I could think of short of a faulty EGR is that I did a coolant bypass after I did the V6 TB swap and use a 5/16 size hose instead of a 3/8. Would that cause the EGR to read improperly or does it not matter? I think I might be having an emissions test in April since the last emissions I had was 2008, and I would really like to get the code out of the way before I go to get the car tested. Thanks.

[mko]

I dont think the coolant lines have to do with this. This either EGR, IAC or MDP sensor problem. They all connected. Clean the EGR see if it comes back

[4g63lover]

Mdp?

[mko]

manifold differential pressure sensor

[fatal1]

catalist ineficiency would point to you exhaust. whether it is an 02 sensor or the cat itself. the mdp is similar to a map sensor it is the one on the intake manifold. iac would point to your maf more then likely...i would try and clear the codes and see if they come back...sometimes a lot of these things have a way of just clearing themselves and require no actual work. as long as you havent noticed any difference as to how your car is driving/acting that is

[stvn_mj]

I had the IAC, tps and mdp codes for months. I swapped in the v6 tb with the tps and iac and also swapped the mdp sensor for another one i bought one day prior to having to test my car at the emissions station. The codes where gone and when it got tested no codes came up and i passed I was so relieved.

[troubled4g64t]

I had this same thing on my car it was catalyst efficiency below threshold bank 1 I changed the o2 sensor and found out that the main cat was no good I also took the iac apart and cleaned it with carb cleaner they both cam up at the same time and both codes showed up after my alt. died and pretty much killed the battery so I don't know if it voltage related like a voltage drop throws the iac wacky causing the cat to plug or something

[RedGalant2k1]

catalist ineficiency would point to you exhaust. whether it is an 02 sensor or the cat itself. the mdp is similar to a map sensor it is the one on the intake manifold. iac would point to your maf more then likely...i would try and clear the codes and see if they come back...sometimes a lot of these things have a way of just clearing themselves and require no actual work. as long as you havent noticed any difference as to how your car is driving/acting that is

Not necessarily, it could be a voltage problem in the wiring and have nothing to do with the exhaust itself. Though you are correct on the likely causes.


I had this same thing on my car it was catalyst efficiency below threshold bank 1 I changed the o2 sensor and found out that the main cat was no good I also took the iac apart and cleaned it with carb cleaner they both cam up at the same time and both codes showed up after my alt. died and pretty much killed the battery so I don't know if it voltage related like a voltage drop throws the iac wacky causing the cat to plug or something

Sure a possibility, get the charging system checked. Improper alternator or battery voltage (or a shorted battery) could absolutely cause these problems.

[4g63lover]

I've cleaned the MAF when I still had the I4 TB, it got rid of the code for a while but it came back. I had this catalyst code after I did the coolant bypass and TB swap. Idle air control code came up after the TB swap and the catalyst after the coolant bypass. I have stock exhaust except for the axle-back portion. I'm going to see if I can get them deleted and see if they come back. I havent got the notice for emissions so I have a little bit of time.

How would I go about cleaning the EGR? and does anyone have a working V6 IAC theyd like to let go for cheap? I'm replacing the hose either tonight or sunday and see if that changes anything.