Catalytic converters.

[Paul Higg]

Can anyone tell me what this is all about? I had my emissions test done today and the NO was a little high. The guy that did it was a Vette guy and he said there could be three reasons. The engine may be running too lean, possible bad EGR, or the catalytic converters going bad.

Now this is where I need enlightenment.

He said something about the cats should be hotter on shut down that when they were running or SOMETHING like that. Can anyone give me the scoop on this?

Thanks.

Paul

Oh, Junk, today I removed and cleaned the IAC, it was very sooty. I also removed and cleaned the EGR and it was a disaster in there. It took almost an entire can of degreaser to clean out the gunk in there. Then I removed the air bridge going to the throttle body and opened the butterflys and looked inside and it was full of black gunk. So I started it and opened the butterflys and sprayed some carb cleaner in there while it ran. I was told this would not be a problem but I would have to pour gallons of the stuff in there to clean it out. Someday I might remove it and clean it. 90,700 on the clock, LT1.

 

[gmjunkie]

Oh, Junk, today I removed and cleaned the IAC, it was very sooty. I also removed and cleaned the EGR and it was a disaster in there. It took almost an entire can of degreaser to clean out the gunk in there. Then I removed the air bridge going to the throttle body and opened the butterflys and looked inside and it was full of black gunk. So I started it and opened the butterflys and sprayed some carb cleaner in there while it ran. I was told this would not be a problem but I would have to pour gallons of the stuff in there to clean it out. Someday I might remove it and clean it. 90,700 on the clock, LT1.

Was that before or after your Emissions Test??

 

[Paul Higg]

Oops, BEFORE the test.

 

[gmjunkie]

Oops, BEFORE the test.

You need to put at least 100-120 miles of normal to get the ECM to relearn everything after doing that!! It probly won't take that long,but I like to make sure!!I drove JimmiJams car to Charlotte and back after doing the work on it,I had to go anyway so I drove it just to make sure it wouldn't trip a code!!

 

[Paul Higg]

But the battery was never disconnected. Does that make a difference?

 

[Paul Higg]

I'm gonna go down in the garage and pull codes and see what I see.

 

[gmjunkie]

But the battery was never disconnected. Does that make a difference?

Doesn't matter,When you sprayed and cleaned the throttle body running,It changed settings in your computer from the cleaner running through it,(Fuel Trim,Timing among other things!) so now you'll have to drive it till it relearns what the engine is actually doing!!

 

[Paul Higg]

I just pulled codes Junk and all I got was an H48. Am trying to look it up. Think the cats could be going bad or the EGR. The EGR was a MESS!

 

[Paul Higg]

Dang! I can't find DTC code 48 ANYWHERE! It was in module 4. Any clues?

 

[gmjunkie]

I just pulled codes Junk and all I got was an H48. Am trying to look it up. Think the cats could be going bad or the EGR. The EGR was a MESS!

H48 is History of mis-fire symptom!! That means that it was a Missing but now it's not!!!(I'm sure it missed like hell while you were cleaning the throttle body!!)You Need to drive the car normally and then it should be alright!!

 

[Paul Higg]

Sorry Junk, but what do you mean by a miss? One thing that did happen was when my wife and I drove from our garage to the end of the subdivision and I had to accelerate from 0 to 55 because that's how fast you have to be when you leave the subdivision I heard a pop and kind of a stall then it was fine after that and then it passed emissions right after that.

Could that be the miss your were referring to?

 

[Paul Higg]

Also, why doesn't it show DTC 48 in the FSM?

 

[gmjunkie]

Sorry Junk, but what do you mean by a miss? One thing that did happen was when my wife and I drove from our garage to the end of the subdivision and I had to accelerate from 0 to 55 because that's how fast you have to be when you leave the subdivision I heard a pop and kind of a stall then it was fine after that and then it passed emissions right after that.

Could that be the miss your were referring to?

That could be it,Yes!! But what I was really talking about your Lean condition is probly caused by you cleaning the throttle body Running!! The Oxy sensors pick up the cleaner and Thinks it's Way Rich,so then it tells the ECM and it makes Drastic changes to compensate and makes it lean,So now the ECM has to relearn the premiers to get back where it was!! Drive it Normally a day or two,If it don't set the Check Engine Light it will be OK!!

 

[Paul Higg]

Yeah, that sounds logical. Junk, again you are the Corvette GURU! We drove it on several errands and had no problems whatsoever, and it was in the 90's. The fuel pump makes it start up so fast I almost now hold the key too long! Plus, the transmission service makes it seem like I am driving a different car!

But why doesn't my FSM not have code 48? Am I not looking in the right place?

Hey, BTW, I went to your site when I clicked on your avatar. I don't know if I told you but your philanthropic work is wonderful. You are a very generous man. I don't know how you feel about God, but I am a believer and someday you will be rewarded for the work you do. I didn't know you did so much to help others outside of the forum.

Now, again, why can't I find code 48? I am baffled.

 

[Vettelt193]

a general rule of thumb after that kind of work is to disconnect the battery to let the computer reset. This way it starts off with a clean slate.

Considering the carbon buildup you have I would also put 2 bottles of Techron in your tank when you fill up. Run that tank down and check the oil. I put money that the oil turns black from all the junk in your fuel system. Assuming it turns black, change the oil and you should be good to go.

 

[Paul Higg]

I had been putting Lucas in the tank for the past few fill-ups and when I changed the oil yesterday it was BLACK!

Thanks for the advice.

Paul

 

[jmhorn52]

I have a question with my 88 coupe with an auto. My car showing a code 32 EGR my mechanic reset it and it was off for a while now the service engine light is on continuously. I havent had the code checked but my guess its the EGR. When the car first starts very strong gas smell Is that the EGR Car runs good and yesterday was averaging between 24-25 MPG at 65-70 mph. Thanks for any help
John

 

[tchort]

I have a question with my 88 coupe with an auto. My car showing a code 32 EGR my mechanic reset it and it was off for a while now the service engine light is on continuously. I havent had the code checked but my guess its the EGR. When the car first starts very strong gas smell Is that the EGR Car runs good and yesterday was averaging between 24-25 MPG at 65-70 mph. Thanks for any help
John

John: I've scanned a couple pages out of my FSM on a "code 32". Don't really know how to upload them here, but I can e-mail them to ya. Shoot me an e-mail at gdstation-cars@yahoo.com