Originally posted by 420AYE
This is what i've found out. On my car, the stuttering is related to rpms. You guys already know that. but i've also found that the stuttering eases at 3500-4200 range. this is where we have the most torque. Something else i've found is right when i start my car up, the car idles perfect, no stuttering. when i push on the peddle a little bit, up to around 2500, and leave it there, the idles will fluctuate about 500 rpms without me moving my foot. they will just go up and down until i let off or push it in farther. The hesitation usually occurs when the car is under a heavy load, and instead of giving that growl noise when accelerating, it just bucks, hicups and hesitates. If i go up a steep hill it will always hesitate, unless i can downshift and get it into that max tq rpm range. if its over or below that range it misses. I have extreme power loss when like this. You guys probably know that point in the peddle, the last little bit that when your in 5th gear, trying to pull a hill, the last bit of the peddle makes no visible difference. I can floor it and the rpms will slowly go up. and then i can 3/4 throttle it and they will go up at the same speed. but the only difference is that when i'm WOT there is hesitation, at 3/4 there isn't. So i'm thinking airflow also plays another part. I'm going to check all my battery connections, test my copmression, get new plug wires and see what i find. If anyone else expieriences these same symptoms let me know what you think. This is a mild/serious problem with us 420a 2g's, and am wondering if it has something to do with the ecu. anyone running a howell ecu got these problems?

Ok my turn. I've read thus entire post. I have a similar issue. 99 Gs mtx. Idle, partial throttles and clutching. Seems there are 4g63, 420a turbos and 420a's in this post. Code for Ses light that I have is bank01 rich. I found that my egr hose was worn and broken. I've replace that and still same symptom but it has helps the idle. I'm leanin towards my tps and or cps. I'll unplug my 02 sensor this evening and pull codes again. By the by my pocketlogger is showing unregistered today so I'll have to go to Autozone to pull the codes quicker. If you have this problem regap your plugs, check the wires for arching and look for broken air hoses. Those should always be 1st on the list for high mileage vehicles.
I'll keep ya posted.