I have a 1998 SC2 with a 5 speed. It has 181k. The car runs great until it warms up. It hesitates and stutters between 1800 -2600 rpms under load only. The car idles fine and I dont have the common surging problem. I have read a lot of posts about this problem and it seems that everyone has a lot of suggestions, but has anyone ever had this problem and successfully fixed it?
Edited by: sw2cam

 

Please tell me what you have tried, this is what *hasn't* worked yet for me:

ECU
Coil packs
Ignition Module
Ignition Cables
Ignition Plugs
Throttle Position Sensor
Engine Coolant Temperature Sensor
Crank Angle Sensor
Clean and inspect Exhaust Gas Return valve
Clean and inspect Idle Air Control valve
Fuel Pump with Strainers
Fuel Filter
Switching Traction Control on/off
Switching Cruise Control on/off

Things left to try:
Air Temp Sensor
Mainfold Air Pressure Sensor
Injectors
Fuel Pressure Regulator
Knock Sensor
Search for Vacuum Leaks
Search for Bad Electrical Connections


Facts:
Lots of people are having the same problem.
It is not intermittent but very specific in its occurrence.
It only happens when the engine has warmed up (and gone into closed loop mode).
Once the problem starts, noone has ever had it fix itself.
Nothing specific was dome to the car before the problem occurred that people can agree on.
It happens to cars that have existed for quite a while. Something is causing fuel not to be present or not burn at some specific operating point.
The operating point appears to be only on throttle position increase, at relatively low RPM.
To some extent the problem appears on the highway at cruising speed, but a much smaller effect.
On throttle position increase, a greater air mass enters the cylinders, proportionally more fuel should be injected to get stoichiometric ratio correct.
Noone here has an answer.

Possible problems relating to operating-point-specific misfires:
Possible problem 1: not enough fuel is entering to match the air intake, causing a lean cut.
Possible problem 2: excessive fuel is entering the cylinder to match intake, making mixture too rich to burn.
Possible problem 3: The stoichiometrically correct mixture is too dense for the spark energy to ignite.

Now, everyone think really really hard about it and see what you come up with!!Edited by: jilbruke

 

Got the same problem....replaced about every sensor except for the ECM....still hesistates when hot.....

I hope there's an answer.....I'm beginning to think it's a vacuum leak somewhere near the fuel tank with all of the vacuum lines and sensors around that area...

 

Okay I'm going to try to post my answer again, even though I've had it deleted a number of times already...

Check your firing order and make sure all plug leads go to all the right cylinders. Don't be fooled into thinking that if it's just on the right coil pack then it'll be fine. The wasted spark ignition in this car doesn't have enough energy in reverse to ignite some mixtures. My problem ended up being that cyl 1 and 4 leads were reversed.

I'm gonna stop there in case they decide to delete the post again, reply if that doesn't make sense and I'll try to add more information.Edited by: jilbruke

 

Nine time out of ten, a faulty coolant temperture sensor will cause this.

 

Check your plug wires, making SURE that they are where they are supposed to be......

I just fixed my car with the same symptoms.....

Changed everything without checking the obvious.....

Sure enough, the wires were not where they were supposed to be...

Car runs great!!