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Don Knight
Don Knight, ASE Certified Technician
Category: Saturn
Satisfied Customers: 1736
Experience:  40+ years
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Saturn LS: 2000 Saturn LS 2.2L Automatic. Engine idles great

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2000 Saturn LS 2.2L Automatic. Engine idles great and runs fine at part throttle. If I start off with anything but very light throttle, the engine surges back and forth. No codes and it has a new TPS. Only thing a bit out of the ordinary is that the coolant temp only gets to 170 degrees.
Welcome to JustAnswer, my name is XXXXX XXXXX I'm here to help get your problem solved. It sounds like you may have a clogged converter, remove the front oxygen sensor completely from exhaust "not just unplugged" and let me know if that helps. Thanks.
Customer: replied 4 years ago.

Took the front O2 sensor out. Same thing. I even did a back pressure test and not even 1/4 psi of back pressure. It almost feels like someone shuts off the ignition for a split second and turns it back on. But only under full load???

Try to spray fuel into throttle body and see if that allows rpm to go higher, that will let us know if problem is fuel related or ignition related. Thanks.
Customer: replied 4 years ago.

You mean at idle?


Someone else will need to be in car pressing gas while you spray fuel into the throttle body then you can see if you can get rpm above part throttle. If that only happens under load let me know. Thanks.

Customer: replied 4 years ago.

When the car is not moving, I can get the rpm to increase all the time. Also, when I put it in gear and press the brake down and hit the gas pedal it goes to torque converter stall speed without hesitation. Only when under real load and heavy acceleration it will surge and eventually reach full rpm.

Ok, now I understand. Have spark plug wires been replaced recently?
Customer: replied 4 years ago.

No, nothing recent. And no misfire codes. ST and LT trim are all ok as well.

Are you able to monitor live misfire data?
Customer: replied 4 years ago.

Yes. At idle, no misfire. In neutral at any rpm - no misfire. Whne it surges under full load, it will give a 1 misfire count randomly, but no repeated misfires.

There are a few things that come to mind here. Poor ground for ignition module, spark plug wires, poor ground going to ignition module. I would replace spark plug wires and run additional ground to ignition module. If that doesn't help replace the ignition module. Let me know how it goes or if you have more questions. Thanks Tom.
Customer: replied 4 years ago.

There are no spark plug wires as it is coil on plug. If the ignition were the problem, would I not see multiple misfires.

Sorry about that, I was thinking about the other engine. I would go ahead and replace the ignition module if running a additional ground doesn't work. If it was anything else such as weak fuel pump it would change fuel trims. You can unplug the mass airflow sensor to see if that helps, if so replace but that usually turns on check engine light too. Let me know how it goes or if you have more questions, thanks.
Customer: replied 4 years ago.

I will do as you suggest. Just one question though. If the ignition module were bad, would I not see misfires on the monitor?

Not always because its not really misfire, its more being limited. If the ignition module and ground do not help I am out of ideas. Let me know how it goes, thanks Tom.
Customer: replied 4 years ago.

Ok, cannot find a MAF on this engine. I changed out the ignition module and confirmed a good ground. Still the same. One thing that is interesting. Once I am in cruising mode, I can give it full throttle and no hesitation or surge. I even tried disconnecting the VSS - but still the same.

Ok, I'm really not sure what to think of this one. I'll open question up to see if someone else has some ideas. Do not reply or question will be locked to me only, someone will respond automatically when they can help. Thanks Tom
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Customer: replied 4 years ago.

First let me say that the professional here, Dan, was very helpful and timely and deserves an excellent rating. Some problems, especially sight unseen, really are difficult to solve and I feel he withdrew only to see if someone else could help.


Yes, I would still like some help. Thank you.


Thank you, XXXXX XXXXX continue to look for a professional to assist you. Please let me know if I can be of any further assistance while you wait.

Good morning.There is a service bulletin on this type of problem.It involves the fuel system and can be caused by either the fuel return line or the jet valve on the fuel pump module.The test calls for you to hook up a fuel pressure gage and have it routed so that you can monitor fuel pressure while driving.If the fuel pressure drops below 39 psi when the problem arises then your problem is in the fuel system.I have had a few of the Saturn's give me this type of problem which is why I remember what was causing the problem.If you do find the fuel supply to be your problem just replace the module and that should take care of your problem.Please let me know if you need any more assistance,Don
Customer: replied 4 years ago.

Thank you for your answer. I hooked up a fuel pressure gauge while driving and sure enough the fuel pressure drops drastically when the surging is present. I have ordered a new fuel pump.

Glad to help.Hope the repairs are easy.The first one of these I fought with for a few days.Thought I was going to loose what little hair I have left.Please let me know if you need more help and if not please dont forget to rate my service.have a great day,Don
Don Knight, ASE Certified Technician
Category: Saturn
Satisfied Customers: 1736
Experience: 40+ years
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