View Full Version : Hesitation Between 2000-3000 RPM!
I'm currently seeing hesitation on a 2001 Grand Am GT with 100,000 miles, but only in the 2000-3000 RPM range! This has me stumped. The spark plugs, spark-plug wires, O2 sensors, EGR valve, and fuel filter are all new as I've been catching up on maintenance and curing other problems on the car. Any ideas out there?
06-05-2007, 10:57 PM
Kind of like it surges about 200 RPM when going up a slight grade?
06-05-2007, 11:18 PM
thats the same thing my car is doing also...Any info?
06-05-2007, 11:54 PM
Sounds like a clogged cat to me.
06-06-2007, 01:15 PM
does this happen in 3rd gear? If so wasnt there a thread about it .. i think you need to re-program your pcm
I've considered getting the fuel injectors professionally cleaned off-car. I've also considered getting a muffler shop to test the pressure before and after the cat to see if there's restriction there.
It's just weird that the engine has no power in just particular RPM range alone. It goes to sleep as soon as it hits 2000, crawls its way up to 3000, and then comes to life!
06-06-2007, 09:52 PM
Andrew, that's your TCC unlocking and locking because you're using the cruise control. Its much like the transmission hunting for gears.
To OP, this sounds like an ignition control issue to me. Likely related to the 24X crank sensor or its reluctor wheel behind the crank pulley. I only say this because I've seen one car with a bad 24X crank sensor have similar problems.
I can't guarantee this will work at all as I can't recall which crank sensor the car can run without, but try this. Start the car and let it idle. Unplug the 24X crank sensor and see if it still runs. If the car doesn't die and stays running when you put it in gear, plug the 24X crank sensor back in and find a big empty parking lot to use. Unplug the sensor again while the car is running and get her up to 3 grand.
If the car doesn't misfire between 2 - 3000 rpms I'd suggest that you remove your crank pulley to inspect or replace the crank sensor or its reluctor ring.
The 24X crank sensor connector is located above the oil filter and next to the knock sensor. It will be a 3 wire connector. Just try not to burn yourself on the exhaust manifold.
Inspection of the crank-position sensor makes a lot of sense.
If there are multiple engine-speed sensors, each of them dedicated to a particular range of engine speed, failure of one sensor would explain why the symptoms are confined to just one range of engine speed.
I'll check this out when I get home from work tonight.
I unplugged the three-wire electrical connector for the crank sensor, the one that runs behind the crank pulley/harmonic balancer. I believe this is one and the same as "crank-sensor A", or the "24x crank sensor".
The car runs the same with it plugged or unplugged!
The service manual says a malfunctioning crank sensor can cause misfiring and P0300, which appears to be the underlying cause of the poor acceleration in that one particular RPM range.
Before I remove the crank pulley/harmonic balancer and replace the CKP, I'd like to see if I can get someone with the same car to unplug theirs to see if they get the same drivability symptoms as me. Also, I think you need a fancy scan tool to run the CKP learn procedure.
06-09-2007, 01:04 AM
Yes you need a Tech 2 to run the CKP Case learn. Its not necessary unless something has been modified involving the crank sensors.
The fact that your car runs the same means the 24x sensor is not at fault. Don't worry about messing with the pulley. The only other option I can postulate at this point is the ignition control module which is underneath the coils.
I'd have to see the car because this is awful specific.
06-10-2007, 05:01 PM
well it depends on what you mean by surging, alot of times that is caused by a clogged fuel filter as well, alot of times we over complicate the easy fix, i have an 02 taurus that would surge from 45 shifting into 2nd only above 3k and the fuel filter fixed it
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