This is for a 99 Vette A4 Switched them out last night had no problems during install. Start the car up and idleing funny no sensor problems or nothing. car was on for a good 10 min idle went up then down up then down i reved my engine a lil and soundend like a whistle. i did not have a Torque wrench i just hand tightend them. i come to check it this morning and check enging light is on. and idle is going up then down up then down..... HELP would be very ...uhh helpfull

 

You probably have a vacuum leak. Please check the DIC for any codes and post them so we can see what the computer is telling you.

BC

 

How do i check the DIC Codes??

 

The whistle is likely caused by one of your gaskets getting sucked in, you could try re-tightening the bolts but I would say you would be much better (safer) to remove the manifold and start over. You should also buy/borrow/rent a torque wrench good for 18 foot lbs (double check that setting though, I'm going by memory).

 

Did you get the very small vac. line/hose on the rear of the intake connected????

 

Exactly what happened to mine. Put in new gasket and works fine.

 

when I did mine, I overlooked the rear vacumn line and had the same condition you report. Check it out and by all means use a torque wrench to tighten the bolts.
Joe

 

Well i We did EVERYTHING, this time in daylight. everything like it said on LS1howto.com the check engine light was still on. i drove around for a good 4 min. everything seemed normal assept at stops it acted like it wanted to stall. then i took it to auto zone. they did a check it was 2 of my o2 sensors and multi cylinder mis fires. they said i need new spark plugs. Car has 49k miles spark plugs havent been changed yet and do push it a lil. could it be that or need gaskets?

 

Sounds like a plug wire just isnt connected completely. Does your A/c only blow on defrost? If that is the case, the rear vacuum hose isnt connected (the stupid dealer didnt put mine back on when they replaced the fuel sending unit sensor, had to fix myself)....My guess would be when you pulled the plug wires, you didnt quite get it put back on the coil or the plug completely

Daren

 

Recommendation. Get an ohm meter and read the resistance of your spark plug wires. Each wire should be between 250 and 600 ohms. If it is greater than that the wires are shot. While you are at it, change the spark plugs. MAKE SURE the engine is C O L D before you remove the plugs or you colud strip out the heads. Also recommend torqueing the plugs rather than just tightening them.

Check your codes using this procedure.

Obtaining Vehicle Codes from the DIC


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:

Turn on the ignition but don't start the engine.
Press the "reset" button to turn off any warning messages
Press and hold "options" and
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.

The codes should tell you what is wrong.

BC

 

If you have a loose plug wire you will know it at more than just idle. The LS1 runs like crap on 7 cylinders (I found out the hard way).

If you have just put an LS6 intake manifold on a 99 345 LS1 it is now getting much more air into it and it will think it is running lean. It will drive your 02 sensors nuts.

I had the same thing happen on my 00. After the mods I took it to a good tuner and all of that went away, plus I'm getting as much as possible out of the mods I paid for.

Working in daylight....

Auto Zone on a Corvette....

 

I don't think he's talking about having Autozone work on the car. He probably went there to pull the codes. Autozone parts counter will let you use a scan tool for free, in the hope you will buy the needed parts from them. If you leave a deposit, they will even let you take it home, use it and return it for a full refund of your deposit. ($150). I know we don't need it on the C5, but it came in handy this weekend while I was working on my daily driver.

 

Sounds like he has more than one issue going on at once. Please post your codes so we can see what is going on and provide advice.

If he disconnected the wires it is totaly possible to have a bad wire. Vacuum leak is another very real possibility!

The code will help narrow stuff down!

BC