Greetings,

'02 Galant ES 2.4L, 127,000

Sorry in advance for the length of this post, trying to give as much pertinent info as possible.

Last week I had an issue with the Galant as I was getting onto the freeway. Leaving work, I have about a 5 minute drive to the freeway entrance on-ramp. The car ran fine through the city streets and at idle during the traffic light. As I was about the merge into the flow of traffic, I got on it as usual to get up to speed with the flow and the car stuttered (didn't cut out) and I backed off the accelerator and it seemed to even out. I couldn't accelerate much more though, and cruised at about 55 Mph on the ride home, about 7 miles.

I had to work the next day and got a ride to work, and I let the car sit until Sunday. Went out Sunday, and let the car warm up to operating temp (needle just short of half-way on temp gauge) Let is idle for about 20 minutes. Warm-up idle was about 1100 for the first few minutes, then dropped to about 850. This is when I noticed a sporadic drop in the idle. About every 10 or 12 seconds there was a slight stutter, then smoothed out. I put the car under load and the rpm dropped to about 650 and the intermittent stutter was more noticeable.

Let the car sit for about an hour and went back out to run it again with the same behavioral results as before. Let it get to operating temp again and decided to drive it on city streets. Didn't have any problem with acceleration. It behaved as described in the prior paragraph at stop lights under load, but it wasn't cutting or dying at the lights. Didn't take it on the freeway that day, but did use some city streets where the speed limit is 50 mph, no issue with cutting out or stuttering at those speeds.

Monday morning decided to take it to work, but deliberately let it get to operating temp before heading out. I've been letting is idle for about 10 minutes before driving it. On-ramp to the freeway is about 1 minute from my house. Had no issue with is accelerating to flow of traffic and drove 65-70 mph to work, behavior at signal lights has not changed under load. Later Monday morning I took it to a auto shop to have them check out the possibilities of the idle behavior. 3 hours later they called and advised I need to replace the catalytic converter system in it's entirety. $1,800.00

Got the car back and decided to just use the warm-up method I've been using and contemplate the price quoted. I have a Haynes for this car and did a little research under the symptoms/trouble shooting section and found a section that described the behavior I experienced on the initial trouble the first time. Haynes made reference to the EGR giving this sort of problem when accelerating, which is what I was doing that evening. I have been driving the car daily, just being deliberate with warm-up period. It gives me no problems at highway speed, however the idle at a signal light remains the same.

I have a friend who has been in the auto repair business for 30+ years, however he specializes in transmission work. Ran the scenario by him including what the repair shop quoted. He was skeptical of the catalytic converter being the issue, however he clearly stated to get a second diagnostic opinion from a specialized muffler shop. He was also under the impression that when a catalytic converter gets hot, it typically is more problematic then when warming up.

Work that has been done on the care the past 3 years.
Timing belt replaced
Idle control replaced
Cam sensor replaced
Oxygen sensors replaced (not at the same time, my bad!)
Spark plug coils were replaced about 4 years ago
Spark plus about 2 years ago

I only put about 80 miles per week of usage on this vehicle, just a work car.

So.... what does the Brain Trust think on the forum? Catalytic converter replacement or something less evil.......? Eagerly awaiting your responses.