Took the car out for a drive (about 4 hours) and half way in anytime i slowed below 20mph or was at idle the engine would run horrible and struggle to stay alive but if left at idle would clear itself up than i go to leave for work this morning and it runs horrible again and stalls out what is going on???

A little info 99 coupe just installed intake, 80,000 miles otherwise stock


Bad o2? Or is the maf flipping out from the new intake? <--- wouldnt it correct itself?

 

If you don't know how to do this from the dash DIC let us know. Pulling codes is ALWAYS the first step on issues like this. Could be something as simple as fouled plugs.

 

I do not....first vette only had it for 7 months

 

I had an old jetta and u would put a paper clip in a some fuse and the engine light would blink some morse code telling u any problems....talking about something like tht?

 

Just did the old googlie on pulling codes will give it a shot when i get home

 

Here is what you need to do. Review the video first and it will help make the write up easier to understand.


Here is how to read your codes from the drivers seat.

READING YOUR C5 Engine Diagnostic Trouble Codes (DTC)

This procedure should be carried out any time you experience a problem with your C5. Most inexpensive store bought aftermarket code readers will ONLY read power train DTC’s. Reading the DTC’s with the C5 built in code reader will allow you to read ALL the modules in the vehicle.

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 the OPTIONS button
4) While holding OPTIONS, press FUEL button four times within a 10 -second period.

Initially, the on-board diagnostics go into an Automatic Mode which will cycle through each module and 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 module. ( 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 types 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. There are a few body module DTC’s that if set will prevent the module from operating properly. Once the DTC is cleared, the module will return to full function. This is not true for power train DTCs.

If you have never read and cleared your codes, there will probably be a lot of old history DTCs. It is recommended that you clear your codes and see if any come back during a driving cycle. Those are the ones that you need to concentrate on diagnosing.

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.

NOTE and a WARNING. You can read the DTCs while the engine is running. I pull mine up all the time while driving.
WARNING. Don’t become distracted while reading DTCs while your driving and cause an accident!!!!! Use common sense and drive safe.

These are some very good C5 Diagnostic Trouble Code (DTC) explanation web sites!!! They also explain how to read the DTCs

Here are some very good sites that explain what DTC mean:

http://www.gearchatter.com/viewtopic11755.php

http://www.obd-codes.com/trouble_cod...d-ii-codes.php

Make sure to include the H or C suffix when you post your DTCs!!

NOTE!!! Start the car and let it idle. Then take it for a drive and cause the problem to occur. When you return home pull the codes BEFORE you shut off the engine.


Do NOT discount the codes with the H following them. They can provide an audit trail for issues going on with the car. They ARE important in diagnosing problems.

Post ALL the codes that you pull with the engine running..........

Some codes go away WITHOUT setting an H code when you shut the engine off. You can/could have several codes that will show C or HC that do NOT show when the engine is turned off.

 

idle air controller? dirty MAF?

have you installed or cleaned any thing recently?

 

Thanks dadaroo and yea i installed a new intake and the old.intake was awful dirty

But i drove for about 2 days

 

what intake?

 

Went from a vararam to that fleebay style intake the T with 2 cone filters

 

in that case kind sounds MAF related, you sure you connected every thing so there is no leaks? did you by chance touch the wires in the MAF?

I'd pull the battery cable to reset every thing and go from there

 

I recently had this problem. I cleaned the MAF and Throttle Body with CRC specific cleaners for each. This cleared the erratic idle and stalling issue. Ensure all connections are tight from the air cleaner back to the TB.

Another fella here with the same issue found a vacuum leak as the culprit.

 

Thnx guys ill check all these when i get home

 

as mentioned b4 reset the battery and go from there

 

You may have forgot to install a vacuum line or damaged the MAF. If you look inside the screened portion of the MAF there are 3 real delicate wires with what looks like a diode attached to each wire. Make sure they are there by doing a visual check. Let us know when you find the problem.

 

Soooooo....i popped the hood and immediately saw the coupler from the bridge to the t.b. was off and remembered that i never did tighten it back on.....face to palm


But thanks for the info guys!!! Learned alot about my vette and what it can do/tell me. Glad i made this post!!

 

Glad it was simple. Now for your award------------------------------

 

My rule of thumb is after working on anything car, motorcycle, heavy equipment and a problem occurs the best place to start looking is the last place I had my hands.