I have a 97 A4. Bought it used 5 months ago, and have had this problem since I bought it. When at idle in gear or in park/neutral, just sometimes, the engine begins to shake somewhat like a misfire or gas starvation. It goes away as soon as I give it gas/let off the brake pedal. I have changed plugs twice, and the wires, and the problem still exists. Changed the air filter to no avail. What could it be?

 

Bad MAF? Try cleaning the wire on the inside...

I'm sure someone will chime in soon

Peace
Willfulone

 

I hope someone has an idea, cause it is getting very annoying

 

Is your car throwing any trouble codes that might provide a clue?

Computer Codes for 1981 – 2003 Corvettes

 

PLEASE read and post your DTC codes in the DIC memory. That will allow us to get an idea what is going on!
Here is a cool sites to help you read your codes and figure out what they mean:

This is the absolute best C5 Code web site!!!

http://www.corvettedoctor.com/Codes_Page.htm

Here is how to read the codes.

The IPC display, the 20-character, vacuum florescent screen above the steering column that says "Corvette by Chevrolet" every time you turn on the key, is a powerful device. DIY Service Techs are going to be most interested in the IPC's ability to show diagnostic trouble codes (DTC) for all the modules that transmit them.
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
3. Press and hold "options" and
4. While holding "options", press "fuel" four times within a 10-second period.
Inititially, the on-board diagnostics go into the "automatic" mode which shows each module's DTCs in a pre-set sequence:
· 10 PCM Powertrain Control Module page 6-357 - 6-361
· 28 TCS Traction Control system ABS on page 5-86
· ?? RTD Real Time damping page 3-136 (I do not have this option)
· 40 BCM Body Control Module page 8-405 UTD Page 8-727
· 60 IPC Instrument Panel Cluster page 8-508
· 80 radio page 8-213
· 99 HVAC Heater Vent-Air Conditioning page 1-118
· A0 LDCM Left Door Control module page 8-904 to 8-951
· A1 RDCM Right Door Control Module page 8-904 to 8-951
· AC SCM Seat Control module page 8-1064 -8-1082
· B0 RFA Remote Function Actuation page 8-676
For each module, all DTCs will be displayed. If none are present in a module, you will see "no more codes" on the ICP display.
There are two kinds of DTCs, "Current" and "History," designated with a letter suffix, "C" or "H". A current code indicates that the malfunction is present in the system whose module is displaying data. A history code indicates a problem existed in that module sometime in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it is possible it's evidence of a previous problem, now solved, that was not removed by clearing codes. More likely is that a history code indicates an intermittent malfunction. "Intermittents" are the most challenging DTCs. An intermittent may have happened only once, may have happened more than once but is inconsistent in its appearance or may be happening on a regular basis but not at the time the IPC is displaying codes. History codes can also be caused by a current malfunction in a system that is not operating at the time DTCs are displayed. An example is the rear window defogger which doesn¹t operate until the BCM detects engine rpm. For history codes set by a system 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 IPC has displayed all 11 modules, the system goes into the manual mode which allows selection of each module using combinations of DIC buttons. The manual mode can also be entered at any time during the automatic sequence by pressing any button except "E/M". Once the IPC displays "manual diagnostics," you may select a particular module by pressing the "options" button to go forward or the "trip" button to go back. Once a system is selected and a DTC is displayed, if more than one are present; press "gages" to move forward or "fuel" to go back.
To exit the diagnostic mode at any time, press "E/M". If you want to erase or "clear" codes, press "reset." Clearing a code does not repair a problem. You are simply erasing the evidence of it in the module's memory.
· 10 PCM Powertrain Control Module page 6-357 - 6-361 Domestic
· A=DTC set immediately and MIL is turned on
· B=MIL turned on after 2 consecutive drive trips
· C=After one failure and stored in History MIL not turned on



BC

 

I think you'll need to read the codes, too. Rough idle could be any number of things.

 

My Silverado was doing this (1999) and it was a fuel pressure regulator that was in the process of going south.

 

Try turning heat/ac off, mine does that every so often. Not throwing any codes, but rpm would drop a bit and take a while to catch up. Same as you, only at idle. Doesn't solve your problem, but might make it easier for these guys to help you out

 

Here are the only two codes that are being thrown: PCM 1571 H & RDCM B2265 H.

BTW, What is a Quick Configure? Just when I went to check the codes, (This just happened for the first time ever since I have had my vette) it said "Quick Configure 324111" on the DIC! What is that all about?

 

The 1571 code is ASR desired torque. and is a History code. Please clear the codes out and see what happens.

BC

 

I have cleared the codes over and over and nothing helps. Could it be a bad fuel pressure regulator? Maybe a bad battery, as my voltage is always at 13.1-13.4? Would a bad battery cause the quick configure message? I have never been able to get rid of the 1571 code, it is always there and always comes back.

 

When you clear the codes do the same ones come back as history?

If you think you have a bad fuel pressure regulator, take a reading in the fuel rail schrader valve. You have a vacuum controlled regulator and should see the reading increase when the vacuum is removed. I looked for the operating fuel pressuer but did not see it. It should be around low 40's at idle and high 40's with the vacuul disconnected.

I doubt if it is the regulatod but ya never know.

BC

 

I have no idea what a quick configure message is. Never seen that one before! Your P1571 has to do with a signal that your Power Train Control Module (PCM) sends the Electronic Brake traction Control Module (EBTCM).. The EBTCM is not sending the signal to the PCM.

The EBTCM is E X P E N S I V E $$$$$$$$$$$$ Most of the time that it malfunctions, it does so because of bad connections and bad grounds.

Here is something that I did to fix my 98 MN6 Coupe. I had electrical issues that would make your hair stand on end! Most all of them were caused by BAD GROUNDS!

Check out this post from a while ago:

http://forums.corvetteforum.com/show...al+information

This is a start and you have an older C5 which I see more and more forum members seeing the same types of electrical issues caused by grounds. This fix is free and easy! I recommend taking a look at the grounds! The two grounds behind the rear wheels are where your EBTCM is grounded to!

Here is a picture of one of them.

[IMG][/IMG]

 

1571 always shows as a history code, and never as a current code. It will not disappear.

I had fuel pressure checked last month, and at idle in park or drive, was at 55 psi - 60 psi. Never changed based on gear change or gas pedal increase. I have never been able to find out the correct fuel pressure(s) so I do not know if the regulator is bad.

 

The only time mine has run bad was with a loose spark plug wire. But it sounded like a dog at any speed with that.

With a 97 your air/fuel mixture might be off and maybe it's tune-up time???????

 

Sounds like my former '89 which symptoms were like fuel starvation (would bog down momentarily until you gave it some pedal) Turned out it was 2 bad injectors.....might be something to check out.

 

I will try to change the fuel pressure regulator. It might help, ut do not know. Hopefully it is inexpensive. I hope someone could chime in that has experienced this, I am on my last leg.

 

I will try to change the fuel pressure regulator. It might help, ut do not know. Hopefully it is inexpensive. I hope someone could chime in that has experienced this, I am on my last leg.

 

I have a BRAND NEW adjustable regulator that i will be willing to sell. Sold my 98 before i could install it!

Bill Curlee.