I am new to this forum, and the corvette community. I recently purchased a blue 2004 targa top with 78k miles. It is automatic, cam, long tube headers, VR cold air intake, 241 cast heads (ported and polished?) and exhaust. I absolutely fell in love with the car. It was also the best value I could find. Here is the negative. And please help.

When I test drove the car, it had been in storage for a while the guy said. I don't know how long. It was traded to a diesel truck dealer so they knew little about the car. The battery was dead, so they bought a new one that day. The car started up right away. It sounded amazing. I put the car in reverse, and it dies. So it does this a couple more times, then after it "warms up" I was able to back. Out and drive it without issue. I was worried, but other than that the car runs perfectly. So I negotiated the price down $1,300 below the lowest kbb price. The next day I drove it fine after letting it warm up for a few minutes. Then today I back it out of the garage, and it dies as I go from reverse to drive. I continue to drive it to work. I go to leave for lunch, and it dies as I put it in drive. It doesn't have a consistent idle. Sometimes it idles at 900 rpm, and sometimes at about 600 rpm. Also the oil psi stays between 50-65, which seems high. My guess is the car needs a tune, but I have no experience with vettes, and little experience with "race cars". I know this is long, but if you need more info ask. I just bought the recommended oil and filter to change since I don't know what this diesel place put in it. Any help will be appreciated.

 

Chris


You have one or several common issues that are easy to check:

1- Examine the PCV rubber fitting on the passengers side of the intake manifold just aft of the throttle body. Make sure that it isn't deteriorated and causing a severe vacuum leak

There are several other mechanical fittings on the complete PCV Pluming that need to be checked for a vacuum leak. Here is your PCV SYSTEM in schematic format:




2- The air ducting between the Throttle Body and the MAF "MUST" be air tight and leak free. Make sure that the fittings between the MAF and TB are properly connected and sealed.

3- Throttle Body Blade and MAF Sense Wires Dirty. Use MAF Spray cleaned and spray the MAF sense wires clean. Clean the Throttle blade while you have the air ducting removed.

Read and post any DTCs that you have. Here's how. If you have a TON of DTCs, clear ALL of them and see what comes back. Report those findings:

READING YOUR Engine Diagnostic Codes


The Diagnostic Display Mode is entered with the following procedure:

1) Turn on the ignition but don't start the engine. NOTE! You can read the DTCs with the engine running and or driving down the road but it can distract you. BE careful! Some DTCs clear themselves when you turn the ignition OFF!

2) Press the RESET button to turn off any warning messages. (i.e. door open, trunk open ect)
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 C code indicates a malfunction is present and active 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 English/Metric (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 and hold the RESET button 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. You can GOOGLE the DTC and also find information on it.




Here is very good site that explains the DTCs:


http://www.corvette-web-central.com/C5DTCcode.html


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



Make sure to include the H or C suffix!!

 

Thanks for the help. I will check everything out that you listed. I checked the codes earlier today. I had no current codes other than one for the drivers seat. I will update after I check everything out.

 

storage car? replace all fluids asap, and in your case, start w/ the gasoline and add treatment when you do it.

 

Fluid here, and a drip under the car around this location.





Inside the Throttle body there was some fluid. I looked inside, and there was signs of fluid inside the intake. Appeared to be oil.





This nipple had no hose or cap. I don't know if it is supposed to be.

 

I cleaned the throttle body up, put everything back ensuring it was nice and tight. I started the car, and it idles at 900-950. I cycle through the gears and every time I change gears the Rpm drops to 500-600, bounces between 550-750 for about 5 seconds, then returns to 950. Also the oil pressure was right at 70 psi on start up. I shut down and checked the codes. I am going to change the oil next to see if that has any affect. Once again no check engine light, no current codes. The car was on 1/2 tank when I got it, and the salesman said that he put 91 octane in it. Later on same day Thursday I filled it up with 91. It clearly is leaking fluids. The oil pan has fluid on it, and if you see the above pictures there is other fluid. I want to add when I am pressing the gas pedal it runs as smooth as possible.

 

You still have not stated that you checked the PCV for vacuum leaks...

The uncapped fitting under the TB is a coolant passage inside the TB that people remove. Its will have ZERO effect on your issue. If its uncapped, it has been bypassed and is no longered used.

The fitting that you show in the pic whr you say theres fluid on the head area, is a steem crossover pipe. Yes, then can leak coolant. Check the tightness of the fastener and if its tight, the gasket under the titting could be bad.

The oil in the intake is from the PCV system.. Install a catch can to help control it.

 

I checked the pcv hoses, they appeared fine. They were secured as well. I had to build some Ramps to change the oil so I am in the middle of that now. I really appreciate the help.

 

Is your car stock or modded and has it ever been tuned??

How many miles on the stock O2 sensors?

Have you ever cleaned the MAF?

BC

 

I had this exact problem with my last vette, ended up being a dead 02 sensor. ...car had long tubes on it without a tune when I purchased it.

 

Wouldn't the car give me a code to work with if this were the problem.

 

Oh I didn't see if u posted ur d.i c. Findings, but yes it should. I had a po134 code on the pcm but no check engine light.

Do u have access to a scanner that's capable of reading ur 02 sensors? Couldn't hurt to double check so u can cross that off the list... I say this Cuz I've seen 02 sensors be bad but still giving a goofy reading as to not throw any codes.

 

Car has long tube headers, cam, 241 cast heads, VR cold air intake, no cats, exhaust. That's all that I know of. I don't know if it has ever been tuned. It has 78k miles on it. I have owned the car for about 5 days.

 

Thanks for the info. Do you now if the scanners at O'reilly or any part store check O2 sensors?

 

No those cheap ones wont. U can check it with hp tuners tho and since u need a tune anyways I'd have ur tuner unlock it and do a road test run b4 any dyno time.

 

I feel like the issue may be getting worse. This morning I started the car let it idle for 3-4 minutes. No issues, I shift into drive idle drops as usual, bounces around goes back to normal. I put it back in park, let the idle stabilize, and I rev it up to about 2000 rpm, then the rpm comes down, and car dies. I repeated this once more, same result. Car dies after reving the engine. At this point I don't feel comfortable driving the car.

 

i didn't think to add this info until now. When I turn the AC on or off it affects the idle a slight bit. I just assumed that was just due to the added workload of the alternator, but maybe it is more significant than I thought.

 

What torque converter are you using? Is sounds to me like you just have a bad tune. When I put a cam in my A4, It took my tuner a couple of times to dial in the "cold start" idle conditions. Once my tune was finalized, he then copied that tune to the "AC on" table so it behaved the same when turned on.

That's my WAG.

 

I have no idea on the torque converter. This is the problem with getting a car someone else built.

 

If the car had a dead battery for a while, as it did, could that cause the computer to forget the tune? That's a long shot I know.