1999 Chevy Prizm – needs a new Catalytic converter

Thank you ToyotaKarl, I’ve noticed you be helpful on many threads and you have certainly added to my learning.

You got me thinking about two things, since my car is obviously suddenly choked up, I’m not throwing the P0420 code anymore, but like I need it, it’s really obvious clogged up at this point.

LOL, I bet since it’s clogged, the 2nd 02 sensor is happy with what is getting through. What little gets through is certainly hot enough to be burned up enough.

My primary concern isn’t about if I replace the catalytic converter anymore, it’s about what damaged it in the first place to not have to simply replace it again. And while reading your comments, it struck me. In 2007 I tried an experiment where you put 1 to 4 ounces of acetone in your gasoline. It reduces the surface tension of the gasoline and can improve efficiency.

True story, it really does work, so far I only see it work on V6’s and up. J&D Power associates gave an award out for how brilliant the fuel injectors are on this car, and it was already perfectly calibrated to fuel so it was a terrible idea. I got 5-7 mpg for about a tank. My next tank I got 17 and then 23 and 27 were starting to be possible again in a few weeks (really poor for this car even in city only driving.)

Edit: my article about Acetone in Gasoline.

I had some symptoms at the time that were similar to now. I think the catalytic converter mostly recovered and I didn’t have any check engine code on it or symptoms for many years to come, but this is why I think my catalytic converter didn’t last the life of the car.

That covers idea 1 that I got going thanks to you.

Idea 2:
It dawned on me that I had the habit of over filling my gasoline tank. I figured, who cares, for the last 9 years my EVAP system was dead anyway. Last couple weeks I stopped since I’m trying to repair the EVAP system with all that was mentioned on my start of this thread. I think my EVAP system is fine now, I just had to stop overfilling now that I expect this system to work. 🙂

[quote=”barneyb” post=95721]The only time I found a charcoal canister bad was a high idle event. The screen in the canister had rusted out (I blame ethanol), the little carbon granules had traveled to the carb and sticking out through the ports they blocked the throttle plate.[/quote]

For a long time I ran 87 octane in my car, but as I upgraded the spark plugs and grounding wires I could no longer see any difference in how the car ran with 85 octane. No mpg difference.

I used to get more mpg with 87, but had found 91 different.

Now that there is consistently more ethanol here in Utah, I switched back up to 87 and performance went up. I believe it has less to no ethanol? Honesty in reporting for what is in gasoline is severely lacking in the current industry.

I live in the U.S. The discovery that it is a 2000 motor was a recent discovery. The car has a rebuilt title and I don’t know if they replaced the ECU/PCM with the engine or not.

A check engine code is what lead me to replace the cam shaft position sensor several months back. A few months ago I noticed a broken wiring harness to an unknown solenoid. 16 hours into trying to find out what it was, let alone who would sell it, I went to the Toyota/Chevrolet dealer in my town and shockingly this part didn’t exist on any of the engine papers.

2 1/2 hours later, with some phone calls for help they found it on engine’s in 2000. It’s simply labeled valve. It’s the valve that runs VVTI though. Note: the valve not running didn’t just affect high rpm performance. It felt like it had high rpm and low rpm modes – my jury rig until the part arrived helped it be energized intermittently and the engine ran rough when under heavy acceleration or at idle depending on which way it was working.

Point is, don’t think this part just helps run the engine when pushed, ignore it and you’ll ruin your valves. 2 weeks into it’s replacement I still occasionally heard valve noises. I’m hoping as they get cleaned up with the fresh oil change that it was gunk and not damage.

I didn’t check engine lights other than after the cam shaft position sensor, I almost wish I had. The whole point in bringing this up was hoping to remember ECU reporting a code or not about the valve to suggest what ECU I had.

Is it possible to assume that since the valve runs at all that I have the right ECU? Pardon they call it PCM on this car.

Foreword: (5 days ago but I couldn’t post at the time)
Forgive me if this was more about the process of discovering solutions instead of having specific questions. I have become a lot more sure of myself thanks to writing down here what I’ve gleaned from my forums. And of course Toyota Karl was very helpful too. I appreciated Barneyb’s feedback as well. I hoped that placing all that happened here might help someone in a similar situation. I put it here for all the dozens of forums I’ve traveled on in the last weeks, this is the only one that I wanted a log in for. I believe a lot broke at once so perhaps that buried “the question”.

Problem 1 What started as a P0420 became obvious when my engine was choking on its exhaust.
My blue tooth active scan obii device arrived last night and the 2nd o2 sensor is all over the place confirming the bad catalytic converter.Your videos are why I’m sure of this thank you.

The 2nd O2 sensor being all over was a little different than your video. Sometimes it’s patterns were opposite of the first O2 sensor and other times it matched. I’m not sure if that means anything more, but regardless the new catalytic converter will be here any day now. (current update, I bought Torque Pro instead of the slower unpaid for android program and it read the active status faster and the first and 2nd 02 pretty much matched confirming the bad cat problem.)

Problem 2 is the EVAP system.
I’m waiting to see what codes come back up now that its all connected and I’ve added not overfilling my tank. Thanks to some answers here I know where to go next to diagnose it.

I ‘ll be report back what happens next there.

Problem 3 MAF P0100 and P0101
I think I killed it with MAF cleaner. A new one will be in tomorrow. (current update: when the MAF was replaced my car no longer “choked” so my catalytic converter may have never been severely clogged up, but it’s going in today.)

Problem 1 Solution:
When I’m done installing the catalytic converter today I wanted to include what I got from the Eastern website for proper break in procedure. http://www.easterncatalytic.com/education/tech-tips/proper-break-in-can-prevent-future-problems/

First I’ll warm up the engine for 5 minutes just letting it idle.
Then I’ll run the engine for 2 minutes at 2,500 rpms.
Finally, I’ll let the catalytic converter cool before driving.

…lastly, I’ll get that EVAP system running right ASAP, I know that it can cause the catalytic converter to go if it has been running open too much creating a rich condition (this is probably what finished the catalytic converter off since I installed it just before all of this started.)

Thanks again for all the great videos Eric. Over the last few weeks I’ve developed a firm goal that I’ll become an Automotive Technician. Increasingly, it has been a beloved hobby for 17 years. ETCG1 videos have been of great help too.

P0420 solved. 🙂

My 1999 Chevy Prizm runs so much better. The old catalytic converter wasn’t melted down or blocked up at all, but it had no efficiency what so ever.

The new converter had the P0420 gone in minutes. I took a risk and went up to a 2 1/2 inch to match my supposed cat back of 2 1/2 inches that was really 2 1/4 inches – that was a lot more work.

It worked out. It has more back pressure than the old catalytic converter, the exhaust sounds quieter and has a better flowing sound.

In the end I care more for mpg than anything else, so I’ll report that when I have enough viable data.

My P0446 and P0440 are back so that’s my next problem to finish. I thought, what they hey, that can indicate a minor leak so low and behold the gasket is bad on my gas cap. I’m sure I have solenoid failure so my next item on the agenda is to take the alligator clips I bought and crimp wires in. Take my new little 9V battery and see which solenoid doesn’t click. (I have 2 evap solenoid’s, one under the hood, another next to the canister, and a purge that goes into my intake.

At least seeing my old catalytic converter out I know I don’t appear to have a bad rich condition from my EVAP system.

Next Question
Does anyone know which wires on the solenoids get the 9V juice? Or, where to find out?