my gf's 2001 coupe will be accelerating fine until about 65-70mph then will stop and the car will start bucking(for lack of a better term), then you let off the pedal and try to accerlerate again and it will start moving along just fine. Except for today it then accerlerated to 80mph and stopped and started slowing back down so again let off and it started moving along just fine. This only happens under 1/2+ throttle.
ANY INPUT WOULD APPRECIATED

thanks matt

 

sounds like limp mode (from what i understand of it). sorry i don't know many specifics, but i've heard similar symptoms being attributed to that.

try a search for limp mode or reduced power mode & see if that narrows down your problem.

 

Use the DIC to post all codes, please.

Jack

 

If in limp mode you would see the message reduced power in the dic display. You need to read and post any codes. Here's how:


READING YOUR Engine Diagnostic Codes (DTCs)
The Diagnostic Display Mode is entered with the following procedure:
1) Turn on the ignition but don't start the engine.
2) Press the RESET button to turn off any warning messages. (i.e. door open, trunk open etc…)
3) Press and hold OPTIONS
4) While holding OPTIONS, press FUEL four times within a 10-second period.

Initially, on-board diagnostics go into an Automatic Mode which shows diagnostic codes in a pre-set sequence: PCM - TCS - RTD - BCM - IPC - RADIO - HVAC - LDCM - RDCM - SCM - RFA. All codes will be displayed for each. ( i.e. PCM = 4 codes)
If none are present in a given module, you will see No More Codes on the display.
There are two kinds of diagnostic codes, Current and History designated with a letter suffix, C or ;H. A current code indicates a malfunction is present in the module displaying data. A history code indicates a problem existed sometime in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it's potential evidence of a previous problem, now resolved, that was not removed by clearing the codes.
More likely it's an indication of an intermittent malfunction.
Intermittent codes are the most challenging of the diagnostics. An intermittent code may have happened once, may have happened more than once but is inconsistent or may be happening on a regular basis but not at the time the codes are displayed. History codes can also be caused by a current malfunction in a system that is not operating at the time codes are displayed. An example is the rear window defogger which doesn't operate until the Body Control Module detects engine rpm. For history codes set by a module that does not operate with the key on and engine off, a special diagnostic tool called a Scan Tester is necessary to properly diagnose the malfunction.
Once the system has displayed all modules, it goes into the manual mode which allows selection of each module using combinations of Driver Information Center buttons. Manual mode can also be entered during the automatic sequence by pressing any button except E/M. Once the display shows Manual Diagnostics, select a module by pressing the OPTIONS button to go forward or the TRIP button to go back. Once a module is selected, a code is displayed, and if more than one are present;
press GAGES to go forward or FUEL to go back.
To exit the diagnostic mode at any time, press E/M. If you want to erase codes in a given module, press RESET
To reset the codes once in manual mode, press and hold RESET until it displays NO CODES Press OPTIONS to go to the next module. Repeat the steps until you have reset the codes in all the computer modules.
NOTE!! Only reset the codes IF you want to - it is NOT necessary to do this. Clearing a code does not repair a problem. You are simply erasing the evidence of it in the module's memory. If you clear the code/s, and extinguish the Check Engine Light, your emissions status ready will NOT allow you to pass an emissions test until you have completed the required driving cycles.
Once you have the codes, the next question is: What to do with the information?
First, consult the factory service manual. Any serious C5 Do-It-Yourself owner should invest in the Corvette Service Manual of the appropriate model year. The Service Manual is really a requirement if you want to understand and work on your C5.

Here is very good site of DTC definitions:


http://www.gearchatter.com


Make sure to include the H or C suffix!!

 

Is it an auto? Just asking because Ive heard people describe slipping gears the same way. Accelerates to the top of a gear and doesnt shift to the next (stops accelerating) until you let off and get on the gas again, allowing the trans to shift.

 

Limp mode sounds like it could be it, but it could be a failing fuel pump too. Under load its giving out right?

 

All you'll get is guesses until you post the codes. Follow the instructions in the post above to retrieve them.

 

I vote for fuel filter. Worth a try any way.

 

it's a safety feature to get you to stop driving your girlfriend's car...